Ydb stable 22-4-4322.4.43

x-stable-origin-commit: 8d49d46cc834835bf3e50870516acd7376a63bcf

92 files changed, 17857 insertions, 0 deletions

diff --git a/contrib/go/_std_1.18/src/math/abs.go b/contrib/go/_std_1.18/src/math/abs.go
new file mode 100644
index 0000000000..df83add695
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/abs.go
@@ -0,0 +1,14 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Abs returns the absolute value of x.
+//
+// Special cases are:
+//	Abs(±Inf) = +Inf
+//	Abs(NaN) = NaN
+func Abs(x float64) float64 {
+	return Float64frombits(Float64bits(x) &^ (1 << 63))
+}
diff --git a/contrib/go/_std_1.18/src/math/acosh.go b/contrib/go/_std_1.18/src/math/acosh.go
new file mode 100644
index 0000000000..f74e0b62fb
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/acosh.go
@@ -0,0 +1,64 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// The original C code, the long comment, and the constants
+// below are from FreeBSD's /usr/src/lib/msun/src/e_acosh.c
+// and came with this notice. The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+//
+// __ieee754_acosh(x)
+// Method :
+//	Based on
+//	        acosh(x) = log [ x + sqrt(x*x-1) ]
+//	we have
+//	        acosh(x) := log(x)+ln2,	if x is large; else
+//	        acosh(x) := log(2x-1/(sqrt(x*x-1)+x)) if x>2; else
+//	        acosh(x) := log1p(t+sqrt(2.0*t+t*t)); where t=x-1.
+//
+// Special cases:
+//	acosh(x) is NaN with signal if x<1.
+//	acosh(NaN) is NaN without signal.
+//
+
+// Acosh returns the inverse hyperbolic cosine of x.
+//
+// Special cases are:
+//	Acosh(+Inf) = +Inf
+//	Acosh(x) = NaN if x < 1
+//	Acosh(NaN) = NaN
+func Acosh(x float64) float64 {
+	if haveArchAcosh {
+		return archAcosh(x)
+	}
+	return acosh(x)
+}
+
+func acosh(x float64) float64 {
+	const Large = 1 << 28 // 2**28
+	// first case is special case
+	switch {
+	case x < 1 || IsNaN(x):
+		return NaN()
+	case x == 1:
+		return 0
+	case x >= Large:
+		return Log(x) + Ln2 // x > 2**28
+	case x > 2:
+		return Log(2*x - 1/(x+Sqrt(x*x-1))) // 2**28 > x > 2
+	}
+	t := x - 1
+	return Log1p(t + Sqrt(2*t+t*t)) // 2 >= x > 1
+}
diff --git a/contrib/go/_std_1.18/src/math/asin.go b/contrib/go/_std_1.18/src/math/asin.go
new file mode 100644
index 0000000000..989a74155b
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/asin.go
@@ -0,0 +1,65 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Floating-point arcsine and arccosine.
+
+	They are implemented by computing the arctangent
+	after appropriate range reduction.
+*/
+
+// Asin returns the arcsine, in radians, of x.
+//
+// Special cases are:
+//	Asin(±0) = ±0
+//	Asin(x) = NaN if x < -1 or x > 1
+func Asin(x float64) float64 {
+	if haveArchAsin {
+		return archAsin(x)
+	}
+	return asin(x)
+}
+
+func asin(x float64) float64 {
+	if x == 0 {
+		return x // special case
+	}
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+	if x > 1 {
+		return NaN() // special case
+	}
+
+	temp := Sqrt(1 - x*x)
+	if x > 0.7 {
+		temp = Pi/2 - satan(temp/x)
+	} else {
+		temp = satan(x / temp)
+	}
+
+	if sign {
+		temp = -temp
+	}
+	return temp
+}
+
+// Acos returns the arccosine, in radians, of x.
+//
+// Special case is:
+//	Acos(x) = NaN if x < -1 or x > 1
+func Acos(x float64) float64 {
+	if haveArchAcos {
+		return archAcos(x)
+	}
+	return acos(x)
+}
+
+func acos(x float64) float64 {
+	return Pi/2 - Asin(x)
+}
diff --git a/contrib/go/_std_1.18/src/math/asinh.go b/contrib/go/_std_1.18/src/math/asinh.go
new file mode 100644
index 0000000000..6dcb241c1f
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/asinh.go
@@ -0,0 +1,76 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// The original C code, the long comment, and the constants
+// below are from FreeBSD's /usr/src/lib/msun/src/s_asinh.c
+// and came with this notice. The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+//
+// asinh(x)
+// Method :
+//	Based on
+//	        asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
+//	we have
+//	asinh(x) := x  if  1+x*x=1,
+//	         := sign(x)*(log(x)+ln2)) for large |x|, else
+//	         := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else
+//	         := sign(x)*log1p(|x| + x**2/(1 + sqrt(1+x**2)))
+//
+
+// Asinh returns the inverse hyperbolic sine of x.
+//
+// Special cases are:
+//	Asinh(±0) = ±0
+//	Asinh(±Inf) = ±Inf
+//	Asinh(NaN) = NaN
+func Asinh(x float64) float64 {
+	if haveArchAsinh {
+		return archAsinh(x)
+	}
+	return asinh(x)
+}
+
+func asinh(x float64) float64 {
+	const (
+		Ln2      = 6.93147180559945286227e-01 // 0x3FE62E42FEFA39EF
+		NearZero = 1.0 / (1 << 28)            // 2**-28
+		Large    = 1 << 28                    // 2**28
+	)
+	// special cases
+	if IsNaN(x) || IsInf(x, 0) {
+		return x
+	}
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+	var temp float64
+	switch {
+	case x > Large:
+		temp = Log(x) + Ln2 // |x| > 2**28
+	case x > 2:
+		temp = Log(2*x + 1/(Sqrt(x*x+1)+x)) // 2**28 > |x| > 2.0
+	case x < NearZero:
+		temp = x // |x| < 2**-28
+	default:
+		temp = Log1p(x + x*x/(1+Sqrt(1+x*x))) // 2.0 > |x| > 2**-28
+	}
+	if sign {
+		temp = -temp
+	}
+	return temp
+}
diff --git a/contrib/go/_std_1.18/src/math/atan.go b/contrib/go/_std_1.18/src/math/atan.go
new file mode 100644
index 0000000000..69af860161
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/atan.go
@@ -0,0 +1,110 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Floating-point arctangent.
+*/
+
+// The original C code, the long comment, and the constants below were
+// from http://netlib.sandia.gov/cephes/cmath/atan.c, available from
+// http://www.netlib.org/cephes/cmath.tgz.
+// The go code is a version of the original C.
+//
+// atan.c
+// Inverse circular tangent (arctangent)
+//
+// SYNOPSIS:
+// double x, y, atan();
+// y = atan( x );
+//
+// DESCRIPTION:
+// Returns radian angle between -pi/2 and +pi/2 whose tangent is x.
+//
+// Range reduction is from three intervals into the interval from zero to 0.66.
+// The approximant uses a rational function of degree 4/5 of the form
+// x + x**3 P(x)/Q(x).
+//
+// ACCURACY:
+//                      Relative error:
+// arithmetic   domain    # trials  peak     rms
+//    DEC       -10, 10   50000     2.4e-17  8.3e-18
+//    IEEE      -10, 10   10^6      1.8e-16  5.0e-17
+//
+// Cephes Math Library Release 2.8:  June, 2000
+// Copyright 1984, 1987, 1989, 1992, 2000 by Stephen L. Moshier
+//
+// The readme file at http://netlib.sandia.gov/cephes/ says:
+//    Some software in this archive may be from the book _Methods and
+// Programs for Mathematical Functions_ (Prentice-Hall or Simon & Schuster
+// International, 1989) or from the Cephes Mathematical Library, a
+// commercial product. In either event, it is copyrighted by the author.
+// What you see here may be used freely but it comes with no support or
+// guarantee.
+//
+//   The two known misprints in the book are repaired here in the
+// source listings for the gamma function and the incomplete beta
+// integral.
+//
+//   Stephen L. Moshier
+//   moshier@na-net.ornl.gov
+
+// xatan evaluates a series valid in the range [0, 0.66].
+func xatan(x float64) float64 {
+	const (
+		P0 = -8.750608600031904122785e-01
+		P1 = -1.615753718733365076637e+01
+		P2 = -7.500855792314704667340e+01
+		P3 = -1.228866684490136173410e+02
+		P4 = -6.485021904942025371773e+01
+		Q0 = +2.485846490142306297962e+01
+		Q1 = +1.650270098316988542046e+02
+		Q2 = +4.328810604912902668951e+02
+		Q3 = +4.853903996359136964868e+02
+		Q4 = +1.945506571482613964425e+02
+	)
+	z := x * x
+	z = z * ((((P0*z+P1)*z+P2)*z+P3)*z + P4) / (((((z+Q0)*z+Q1)*z+Q2)*z+Q3)*z + Q4)
+	z = x*z + x
+	return z
+}
+
+// satan reduces its argument (known to be positive)
+// to the range [0, 0.66] and calls xatan.
+func satan(x float64) float64 {
+	const (
+		Morebits = 6.123233995736765886130e-17 // pi/2 = PIO2 + Morebits
+		Tan3pio8 = 2.41421356237309504880      // tan(3*pi/8)
+	)
+	if x <= 0.66 {
+		return xatan(x)
+	}
+	if x > Tan3pio8 {
+		return Pi/2 - xatan(1/x) + Morebits
+	}
+	return Pi/4 + xatan((x-1)/(x+1)) + 0.5*Morebits
+}
+
+// Atan returns the arctangent, in radians, of x.
+//
+// Special cases are:
+//      Atan(±0) = ±0
+//      Atan(±Inf) = ±Pi/2
+func Atan(x float64) float64 {
+	if haveArchAtan {
+		return archAtan(x)
+	}
+	return atan(x)
+}
+
+func atan(x float64) float64 {
+	if x == 0 {
+		return x
+	}
+	if x > 0 {
+		return satan(x)
+	}
+	return -satan(-x)
+}
diff --git a/contrib/go/_std_1.18/src/math/atan2.go b/contrib/go/_std_1.18/src/math/atan2.go
new file mode 100644
index 0000000000..11d7e81acd
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/atan2.go
@@ -0,0 +1,76 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Atan2 returns the arc tangent of y/x, using
+// the signs of the two to determine the quadrant
+// of the return value.
+//
+// Special cases are (in order):
+//	Atan2(y, NaN) = NaN
+//	Atan2(NaN, x) = NaN
+//	Atan2(+0, x>=0) = +0
+//	Atan2(-0, x>=0) = -0
+//	Atan2(+0, x<=-0) = +Pi
+//	Atan2(-0, x<=-0) = -Pi
+//	Atan2(y>0, 0) = +Pi/2
+//	Atan2(y<0, 0) = -Pi/2
+//	Atan2(+Inf, +Inf) = +Pi/4
+//	Atan2(-Inf, +Inf) = -Pi/4
+//	Atan2(+Inf, -Inf) = 3Pi/4
+//	Atan2(-Inf, -Inf) = -3Pi/4
+//	Atan2(y, +Inf) = 0
+//	Atan2(y>0, -Inf) = +Pi
+//	Atan2(y<0, -Inf) = -Pi
+//	Atan2(+Inf, x) = +Pi/2
+//	Atan2(-Inf, x) = -Pi/2
+func Atan2(y, x float64) float64 {
+	if haveArchAtan2 {
+		return archAtan2(y, x)
+	}
+	return atan2(y, x)
+}
+
+func atan2(y, x float64) float64 {
+	// special cases
+	switch {
+	case IsNaN(y) || IsNaN(x):
+		return NaN()
+	case y == 0:
+		if x >= 0 && !Signbit(x) {
+			return Copysign(0, y)
+		}
+		return Copysign(Pi, y)
+	case x == 0:
+		return Copysign(Pi/2, y)
+	case IsInf(x, 0):
+		if IsInf(x, 1) {
+			switch {
+			case IsInf(y, 0):
+				return Copysign(Pi/4, y)
+			default:
+				return Copysign(0, y)
+			}
+		}
+		switch {
+		case IsInf(y, 0):
+			return Copysign(3*Pi/4, y)
+		default:
+			return Copysign(Pi, y)
+		}
+	case IsInf(y, 0):
+		return Copysign(Pi/2, y)
+	}
+
+	// Call atan and determine the quadrant.
+	q := Atan(y / x)
+	if x < 0 {
+		if q <= 0 {
+			return q + Pi
+		}
+		return q - Pi
+	}
+	return q
+}
diff --git a/contrib/go/_std_1.18/src/math/atanh.go b/contrib/go/_std_1.18/src/math/atanh.go
new file mode 100644
index 0000000000..fe8bd6d8a4
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/atanh.go
@@ -0,0 +1,84 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// The original C code, the long comment, and the constants
+// below are from FreeBSD's /usr/src/lib/msun/src/e_atanh.c
+// and came with this notice. The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+//
+// __ieee754_atanh(x)
+// Method :
+//	1. Reduce x to positive by atanh(-x) = -atanh(x)
+//	2. For x>=0.5
+//	            1              2x                          x
+//	atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
+//	            2             1 - x                      1 - x
+//
+//	For x<0.5
+//	atanh(x) = 0.5*log1p(2x+2x*x/(1-x))
+//
+// Special cases:
+//	atanh(x) is NaN if |x| > 1 with signal;
+//	atanh(NaN) is that NaN with no signal;
+//	atanh(+-1) is +-INF with signal.
+//
+
+// Atanh returns the inverse hyperbolic tangent of x.
+//
+// Special cases are:
+//	Atanh(1) = +Inf
+//	Atanh(±0) = ±0
+//	Atanh(-1) = -Inf
+//	Atanh(x) = NaN if x < -1 or x > 1
+//	Atanh(NaN) = NaN
+func Atanh(x float64) float64 {
+	if haveArchAtanh {
+		return archAtanh(x)
+	}
+	return atanh(x)
+}
+
+func atanh(x float64) float64 {
+	const NearZero = 1.0 / (1 << 28) // 2**-28
+	// special cases
+	switch {
+	case x < -1 || x > 1 || IsNaN(x):
+		return NaN()
+	case x == 1:
+		return Inf(1)
+	case x == -1:
+		return Inf(-1)
+	}
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+	var temp float64
+	switch {
+	case x < NearZero:
+		temp = x
+	case x < 0.5:
+		temp = x + x
+		temp = 0.5 * Log1p(temp+temp*x/(1-x))
+	default:
+		temp = 0.5 * Log1p((x+x)/(1-x))
+	}
+	if sign {
+		temp = -temp
+	}
+	return temp
+}
diff --git a/contrib/go/_std_1.18/src/math/big/accuracy_string.go b/contrib/go/_std_1.18/src/math/big/accuracy_string.go
new file mode 100644
index 0000000000..1501ace00d
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/accuracy_string.go
@@ -0,0 +1,17 @@
+// Code generated by "stringer -type=Accuracy"; DO NOT EDIT.
+
+package big
+
+import "strconv"
+
+const _Accuracy_name = "BelowExactAbove"
+
+var _Accuracy_index = [...]uint8{0, 5, 10, 15}
+
+func (i Accuracy) String() string {
+	i -= -1
+	if i < 0 || i >= Accuracy(len(_Accuracy_index)-1) {
+		return "Accuracy(" + strconv.FormatInt(int64(i+-1), 10) + ")"
+	}
+	return _Accuracy_name[_Accuracy_index[i]:_Accuracy_index[i+1]]
+}
diff --git a/contrib/go/_std_1.18/src/math/big/arith.go b/contrib/go/_std_1.18/src/math/big/arith.go
new file mode 100644
index 0000000000..8f55c195d4
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/arith.go
@@ -0,0 +1,277 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file provides Go implementations of elementary multi-precision
+// arithmetic operations on word vectors. These have the suffix _g.
+// These are needed for platforms without assembly implementations of these routines.
+// This file also contains elementary operations that can be implemented
+// sufficiently efficiently in Go.
+
+package big
+
+import "math/bits"
+
+// A Word represents a single digit of a multi-precision unsigned integer.
+type Word uint
+
+const (
+	_S = _W / 8 // word size in bytes
+
+	_W = bits.UintSize // word size in bits
+	_B = 1 << _W       // digit base
+	_M = _B - 1        // digit mask
+)
+
+// Many of the loops in this file are of the form
+//   for i := 0; i < len(z) && i < len(x) && i < len(y); i++
+// i < len(z) is the real condition.
+// However, checking i < len(x) && i < len(y) as well is faster than
+// having the compiler do a bounds check in the body of the loop;
+// remarkably it is even faster than hoisting the bounds check
+// out of the loop, by doing something like
+//   _, _ = x[len(z)-1], y[len(z)-1]
+// There are other ways to hoist the bounds check out of the loop,
+// but the compiler's BCE isn't powerful enough for them (yet?).
+// See the discussion in CL 164966.
+
+// ----------------------------------------------------------------------------
+// Elementary operations on words
+//
+// These operations are used by the vector operations below.
+
+// z1<<_W + z0 = x*y
+func mulWW_g(x, y Word) (z1, z0 Word) {
+	hi, lo := bits.Mul(uint(x), uint(y))
+	return Word(hi), Word(lo)
+}
+
+// z1<<_W + z0 = x*y + c
+func mulAddWWW_g(x, y, c Word) (z1, z0 Word) {
+	hi, lo := bits.Mul(uint(x), uint(y))
+	var cc uint
+	lo, cc = bits.Add(lo, uint(c), 0)
+	return Word(hi + cc), Word(lo)
+}
+
+// nlz returns the number of leading zeros in x.
+// Wraps bits.LeadingZeros call for convenience.
+func nlz(x Word) uint {
+	return uint(bits.LeadingZeros(uint(x)))
+}
+
+// The resulting carry c is either 0 or 1.
+func addVV_g(z, x, y []Word) (c Word) {
+	// The comment near the top of this file discusses this for loop condition.
+	for i := 0; i < len(z) && i < len(x) && i < len(y); i++ {
+		zi, cc := bits.Add(uint(x[i]), uint(y[i]), uint(c))
+		z[i] = Word(zi)
+		c = Word(cc)
+	}
+	return
+}
+
+// The resulting carry c is either 0 or 1.
+func subVV_g(z, x, y []Word) (c Word) {
+	// The comment near the top of this file discusses this for loop condition.
+	for i := 0; i < len(z) && i < len(x) && i < len(y); i++ {
+		zi, cc := bits.Sub(uint(x[i]), uint(y[i]), uint(c))
+		z[i] = Word(zi)
+		c = Word(cc)
+	}
+	return
+}
+
+// The resulting carry c is either 0 or 1.
+func addVW_g(z, x []Word, y Word) (c Word) {
+	c = y
+	// The comment near the top of this file discusses this for loop condition.
+	for i := 0; i < len(z) && i < len(x); i++ {
+		zi, cc := bits.Add(uint(x[i]), uint(c), 0)
+		z[i] = Word(zi)
+		c = Word(cc)
+	}
+	return
+}
+
+// addVWlarge is addVW, but intended for large z.
+// The only difference is that we check on every iteration
+// whether we are done with carries,
+// and if so, switch to a much faster copy instead.
+// This is only a good idea for large z,
+// because the overhead of the check and the function call
+// outweigh the benefits when z is small.
+func addVWlarge(z, x []Word, y Word) (c Word) {
+	c = y
+	// The comment near the top of this file discusses this for loop condition.
+	for i := 0; i < len(z) && i < len(x); i++ {
+		if c == 0 {
+			copy(z[i:], x[i:])
+			return
+		}
+		zi, cc := bits.Add(uint(x[i]), uint(c), 0)
+		z[i] = Word(zi)
+		c = Word(cc)
+	}
+	return
+}
+
+func subVW_g(z, x []Word, y Word) (c Word) {
+	c = y
+	// The comment near the top of this file discusses this for loop condition.
+	for i := 0; i < len(z) && i < len(x); i++ {
+		zi, cc := bits.Sub(uint(x[i]), uint(c), 0)
+		z[i] = Word(zi)
+		c = Word(cc)
+	}
+	return
+}
+
+// subVWlarge is to subVW as addVWlarge is to addVW.
+func subVWlarge(z, x []Word, y Word) (c Word) {
+	c = y
+	// The comment near the top of this file discusses this for loop condition.
+	for i := 0; i < len(z) && i < len(x); i++ {
+		if c == 0 {
+			copy(z[i:], x[i:])
+			return
+		}
+		zi, cc := bits.Sub(uint(x[i]), uint(c), 0)
+		z[i] = Word(zi)
+		c = Word(cc)
+	}
+	return
+}
+
+func shlVU_g(z, x []Word, s uint) (c Word) {
+	if s == 0 {
+		copy(z, x)
+		return
+	}
+	if len(z) == 0 {
+		return
+	}
+	s &= _W - 1 // hint to the compiler that shifts by s don't need guard code
+	ŝ := _W - s
+	ŝ &= _W - 1 // ditto
+	c = x[len(z)-1] >> ŝ
+	for i := len(z) - 1; i > 0; i-- {
+		z[i] = x[i]<<s | x[i-1]>>ŝ
+	}
+	z[0] = x[0] << s
+	return
+}
+
+func shrVU_g(z, x []Word, s uint) (c Word) {
+	if s == 0 {
+		copy(z, x)
+		return
+	}
+	if len(z) == 0 {
+		return
+	}
+	if len(x) != len(z) {
+		// This is an invariant guaranteed by the caller.
+		panic("len(x) != len(z)")
+	}
+	s &= _W - 1 // hint to the compiler that shifts by s don't need guard code
+	ŝ := _W - s
+	ŝ &= _W - 1 // ditto
+	c = x[0] << ŝ
+	for i := 1; i < len(z); i++ {
+		z[i-1] = x[i-1]>>s | x[i]<<ŝ
+	}
+	z[len(z)-1] = x[len(z)-1] >> s
+	return
+}
+
+func mulAddVWW_g(z, x []Word, y, r Word) (c Word) {
+	c = r
+	// The comment near the top of this file discusses this for loop condition.
+	for i := 0; i < len(z) && i < len(x); i++ {
+		c, z[i] = mulAddWWW_g(x[i], y, c)
+	}
+	return
+}
+
+func addMulVVW_g(z, x []Word, y Word) (c Word) {
+	// The comment near the top of this file discusses this for loop condition.
+	for i := 0; i < len(z) && i < len(x); i++ {
+		z1, z0 := mulAddWWW_g(x[i], y, z[i])
+		lo, cc := bits.Add(uint(z0), uint(c), 0)
+		c, z[i] = Word(cc), Word(lo)
+		c += z1
+	}
+	return
+}
+
+// q = ( x1 << _W + x0 - r)/y. m = floor(( _B^2 - 1 ) / d - _B). Requiring x1<y.
+// An approximate reciprocal with a reference to "Improved Division by Invariant Integers
+// (IEEE Transactions on Computers, 11 Jun. 2010)"
+func divWW(x1, x0, y, m Word) (q, r Word) {
+	s := nlz(y)
+	if s != 0 {
+		x1 = x1<<s | x0>>(_W-s)
+		x0 <<= s
+		y <<= s
+	}
+	d := uint(y)
+	// We know that
+	//   m = ⎣(B^2-1)/d⎦-B
+	//   ⎣(B^2-1)/d⎦ = m+B
+	//   (B^2-1)/d = m+B+delta1    0 <= delta1 <= (d-1)/d
+	//   B^2/d = m+B+delta2        0 <= delta2 <= 1
+	// The quotient we're trying to compute is
+	//   quotient = ⎣(x1*B+x0)/d⎦
+	//            = ⎣(x1*B*(B^2/d)+x0*(B^2/d))/B^2⎦
+	//            = ⎣(x1*B*(m+B+delta2)+x0*(m+B+delta2))/B^2⎦
+	//            = ⎣(x1*m+x1*B+x0)/B + x0*m/B^2 + delta2*(x1*B+x0)/B^2⎦
+	// The latter two terms of this three-term sum are between 0 and 1.
+	// So we can compute just the first term, and we will be low by at most 2.
+	t1, t0 := bits.Mul(uint(m), uint(x1))
+	_, c := bits.Add(t0, uint(x0), 0)
+	t1, _ = bits.Add(t1, uint(x1), c)
+	// The quotient is either t1, t1+1, or t1+2.
+	// We'll try t1 and adjust if needed.
+	qq := t1
+	// compute remainder r=x-d*q.
+	dq1, dq0 := bits.Mul(d, qq)
+	r0, b := bits.Sub(uint(x0), dq0, 0)
+	r1, _ := bits.Sub(uint(x1), dq1, b)
+	// The remainder we just computed is bounded above by B+d:
+	// r = x1*B + x0 - d*q.
+	//   = x1*B + x0 - d*⎣(x1*m+x1*B+x0)/B⎦
+	//   = x1*B + x0 - d*((x1*m+x1*B+x0)/B-alpha)                                   0 <= alpha < 1
+	//   = x1*B + x0 - x1*d/B*m                         - x1*d - x0*d/B + d*alpha
+	//   = x1*B + x0 - x1*d/B*⎣(B^2-1)/d-B⎦             - x1*d - x0*d/B + d*alpha
+	//   = x1*B + x0 - x1*d/B*⎣(B^2-1)/d-B⎦             - x1*d - x0*d/B + d*alpha
+	//   = x1*B + x0 - x1*d/B*((B^2-1)/d-B-beta)        - x1*d - x0*d/B + d*alpha   0 <= beta < 1
+	//   = x1*B + x0 - x1*B + x1/B + x1*d + x1*d/B*beta - x1*d - x0*d/B + d*alpha
+	//   =        x0        + x1/B        + x1*d/B*beta        - x0*d/B + d*alpha
+	//   = x0*(1-d/B) + x1*(1+d*beta)/B + d*alpha
+	//   <  B*(1-d/B) +  d*B/B          + d          because x0<B (and 1-d/B>0), x1<d, 1+d*beta<=B, alpha<1
+	//   =  B - d     +  d              + d
+	//   = B+d
+	// So r1 can only be 0 or 1. If r1 is 1, then we know q was too small.
+	// Add 1 to q and subtract d from r. That guarantees that r is <B, so
+	// we no longer need to keep track of r1.
+	if r1 != 0 {
+		qq++
+		r0 -= d
+	}
+	// If the remainder is still too large, increment q one more time.
+	if r0 >= d {
+		qq++
+		r0 -= d
+	}
+	return Word(qq), Word(r0 >> s)
+}
+
+// reciprocalWord return the reciprocal of the divisor. rec = floor(( _B^2 - 1 ) / u - _B). u = d1 << nlz(d1).
+func reciprocalWord(d1 Word) Word {
+	u := uint(d1 << nlz(d1))
+	x1 := ^u
+	x0 := uint(_M)
+	rec, _ := bits.Div(x1, x0, u) // (_B^2-1)/U-_B = (_B*(_M-C)+_M)/U
+	return Word(rec)
+}
diff --git a/contrib/go/_std_1.18/src/math/big/arith_amd64.go b/contrib/go/_std_1.18/src/math/big/arith_amd64.go
new file mode 100644
index 0000000000..89108fe149
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/arith_amd64.go
@@ -0,0 +1,12 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !math_big_pure_go
+// +build !math_big_pure_go
+
+package big
+
+import "internal/cpu"
+
+var support_adx = cpu.X86.HasADX && cpu.X86.HasBMI2
diff --git a/contrib/go/_std_1.18/src/math/big/arith_amd64.s b/contrib/go/_std_1.18/src/math/big/arith_amd64.s
new file mode 100644
index 0000000000..5c72a27d8d
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/arith_amd64.s
@@ -0,0 +1,526 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !math_big_pure_go
+// +build !math_big_pure_go
+
+#include "textflag.h"
+
+// This file provides fast assembly versions for the elementary
+// arithmetic operations on vectors implemented in arith.go.
+
+// func mulWW(x, y Word) (z1, z0 Word)
+TEXT ·mulWW(SB),NOSPLIT,$0
+	MOVQ x+0(FP), AX
+	MULQ y+8(FP)
+	MOVQ DX, z1+16(FP)
+	MOVQ AX, z0+24(FP)
+	RET
+
+
+
+// The carry bit is saved with SBBQ Rx, Rx: if the carry was set, Rx is -1, otherwise it is 0.
+// It is restored with ADDQ Rx, Rx: if Rx was -1 the carry is set, otherwise it is cleared.
+// This is faster than using rotate instructions.
+
+// func addVV(z, x, y []Word) (c Word)
+TEXT ·addVV(SB),NOSPLIT,$0
+	MOVQ z_len+8(FP), DI
+	MOVQ x+24(FP), R8
+	MOVQ y+48(FP), R9
+	MOVQ z+0(FP), R10
+
+	MOVQ $0, CX		// c = 0
+	MOVQ $0, SI		// i = 0
+
+	// s/JL/JMP/ below to disable the unrolled loop
+	SUBQ $4, DI		// n -= 4
+	JL V1			// if n < 0 goto V1
+
+U1:	// n >= 0
+	// regular loop body unrolled 4x
+	ADDQ CX, CX		// restore CF
+	MOVQ 0(R8)(SI*8), R11
+	MOVQ 8(R8)(SI*8), R12
+	MOVQ 16(R8)(SI*8), R13
+	MOVQ 24(R8)(SI*8), R14
+	ADCQ 0(R9)(SI*8), R11
+	ADCQ 8(R9)(SI*8), R12
+	ADCQ 16(R9)(SI*8), R13
+	ADCQ 24(R9)(SI*8), R14
+	MOVQ R11, 0(R10)(SI*8)
+	MOVQ R12, 8(R10)(SI*8)
+	MOVQ R13, 16(R10)(SI*8)
+	MOVQ R14, 24(R10)(SI*8)
+	SBBQ CX, CX		// save CF
+
+	ADDQ $4, SI		// i += 4
+	SUBQ $4, DI		// n -= 4
+	JGE U1			// if n >= 0 goto U1
+
+V1:	ADDQ $4, DI		// n += 4
+	JLE E1			// if n <= 0 goto E1
+
+L1:	// n > 0
+	ADDQ CX, CX		// restore CF
+	MOVQ 0(R8)(SI*8), R11
+	ADCQ 0(R9)(SI*8), R11
+	MOVQ R11, 0(R10)(SI*8)
+	SBBQ CX, CX		// save CF
+
+	ADDQ $1, SI		// i++
+	SUBQ $1, DI		// n--
+	JG L1			// if n > 0 goto L1
+
+E1:	NEGQ CX
+	MOVQ CX, c+72(FP)	// return c
+	RET
+
+
+// func subVV(z, x, y []Word) (c Word)
+// (same as addVV except for SBBQ instead of ADCQ and label names)
+TEXT ·subVV(SB),NOSPLIT,$0
+	MOVQ z_len+8(FP), DI
+	MOVQ x+24(FP), R8
+	MOVQ y+48(FP), R9
+	MOVQ z+0(FP), R10
+
+	MOVQ $0, CX		// c = 0
+	MOVQ $0, SI		// i = 0
+
+	// s/JL/JMP/ below to disable the unrolled loop
+	SUBQ $4, DI		// n -= 4
+	JL V2			// if n < 0 goto V2
+
+U2:	// n >= 0
+	// regular loop body unrolled 4x
+	ADDQ CX, CX		// restore CF
+	MOVQ 0(R8)(SI*8), R11
+	MOVQ 8(R8)(SI*8), R12
+	MOVQ 16(R8)(SI*8), R13
+	MOVQ 24(R8)(SI*8), R14
+	SBBQ 0(R9)(SI*8), R11
+	SBBQ 8(R9)(SI*8), R12
+	SBBQ 16(R9)(SI*8), R13
+	SBBQ 24(R9)(SI*8), R14
+	MOVQ R11, 0(R10)(SI*8)
+	MOVQ R12, 8(R10)(SI*8)
+	MOVQ R13, 16(R10)(SI*8)
+	MOVQ R14, 24(R10)(SI*8)
+	SBBQ CX, CX		// save CF
+
+	ADDQ $4, SI		// i += 4
+	SUBQ $4, DI		// n -= 4
+	JGE U2			// if n >= 0 goto U2
+
+V2:	ADDQ $4, DI		// n += 4
+	JLE E2			// if n <= 0 goto E2
+
+L2:	// n > 0
+	ADDQ CX, CX		// restore CF
+	MOVQ 0(R8)(SI*8), R11
+	SBBQ 0(R9)(SI*8), R11
+	MOVQ R11, 0(R10)(SI*8)
+	SBBQ CX, CX		// save CF
+
+	ADDQ $1, SI		// i++
+	SUBQ $1, DI		// n--
+	JG L2			// if n > 0 goto L2
+
+E2:	NEGQ CX
+	MOVQ CX, c+72(FP)	// return c
+	RET
+
+
+// func addVW(z, x []Word, y Word) (c Word)
+TEXT ·addVW(SB),NOSPLIT,$0
+	MOVQ z_len+8(FP), DI
+	CMPQ DI, $32
+	JG large
+	MOVQ x+24(FP), R8
+	MOVQ y+48(FP), CX	// c = y
+	MOVQ z+0(FP), R10
+
+	MOVQ $0, SI		// i = 0
+
+	// s/JL/JMP/ below to disable the unrolled loop
+	SUBQ $4, DI		// n -= 4
+	JL V3			// if n < 4 goto V3
+
+U3:	// n >= 0
+	// regular loop body unrolled 4x
+	MOVQ 0(R8)(SI*8), R11
+	MOVQ 8(R8)(SI*8), R12
+	MOVQ 16(R8)(SI*8), R13
+	MOVQ 24(R8)(SI*8), R14
+	ADDQ CX, R11
+	ADCQ $0, R12
+	ADCQ $0, R13
+	ADCQ $0, R14
+	SBBQ CX, CX		// save CF
+	NEGQ CX
+	MOVQ R11, 0(R10)(SI*8)
+	MOVQ R12, 8(R10)(SI*8)
+	MOVQ R13, 16(R10)(SI*8)
+	MOVQ R14, 24(R10)(SI*8)
+
+	ADDQ $4, SI		// i += 4
+	SUBQ $4, DI		// n -= 4
+	JGE U3			// if n >= 0 goto U3
+
+V3:	ADDQ $4, DI		// n += 4
+	JLE E3			// if n <= 0 goto E3
+
+L3:	// n > 0
+	ADDQ 0(R8)(SI*8), CX
+	MOVQ CX, 0(R10)(SI*8)
+	SBBQ CX, CX		// save CF
+	NEGQ CX
+
+	ADDQ $1, SI		// i++
+	SUBQ $1, DI		// n--
+	JG L3			// if n > 0 goto L3
+
+E3:	MOVQ CX, c+56(FP)	// return c
+	RET
+large:
+	JMP ·addVWlarge(SB)
+
+
+// func subVW(z, x []Word, y Word) (c Word)
+// (same as addVW except for SUBQ/SBBQ instead of ADDQ/ADCQ and label names)
+TEXT ·subVW(SB),NOSPLIT,$0
+	MOVQ z_len+8(FP), DI
+	CMPQ DI, $32
+	JG large
+	MOVQ x+24(FP), R8
+	MOVQ y+48(FP), CX	// c = y
+	MOVQ z+0(FP), R10
+
+	MOVQ $0, SI		// i = 0
+
+	// s/JL/JMP/ below to disable the unrolled loop
+	SUBQ $4, DI		// n -= 4
+	JL V4			// if n < 4 goto V4
+
+U4:	// n >= 0
+	// regular loop body unrolled 4x
+	MOVQ 0(R8)(SI*8), R11
+	MOVQ 8(R8)(SI*8), R12
+	MOVQ 16(R8)(SI*8), R13
+	MOVQ 24(R8)(SI*8), R14
+	SUBQ CX, R11
+	SBBQ $0, R12
+	SBBQ $0, R13
+	SBBQ $0, R14
+	SBBQ CX, CX		// save CF
+	NEGQ CX
+	MOVQ R11, 0(R10)(SI*8)
+	MOVQ R12, 8(R10)(SI*8)
+	MOVQ R13, 16(R10)(SI*8)
+	MOVQ R14, 24(R10)(SI*8)
+
+	ADDQ $4, SI		// i += 4
+	SUBQ $4, DI		// n -= 4
+	JGE U4			// if n >= 0 goto U4
+
+V4:	ADDQ $4, DI		// n += 4
+	JLE E4			// if n <= 0 goto E4
+
+L4:	// n > 0
+	MOVQ 0(R8)(SI*8), R11
+	SUBQ CX, R11
+	MOVQ R11, 0(R10)(SI*8)
+	SBBQ CX, CX		// save CF
+	NEGQ CX
+
+	ADDQ $1, SI		// i++
+	SUBQ $1, DI		// n--
+	JG L4			// if n > 0 goto L4
+
+E4:	MOVQ CX, c+56(FP)	// return c
+	RET
+large:
+	JMP ·subVWlarge(SB)
+
+
+// func shlVU(z, x []Word, s uint) (c Word)
+TEXT ·shlVU(SB),NOSPLIT,$0
+	MOVQ z_len+8(FP), BX	// i = z
+	SUBQ $1, BX		// i--
+	JL X8b			// i < 0	(n <= 0)
+
+	// n > 0
+	MOVQ z+0(FP), R10
+	MOVQ x+24(FP), R8
+	MOVQ s+48(FP), CX
+	MOVQ (R8)(BX*8), AX	// w1 = x[n-1]
+	MOVQ $0, DX
+	SHLQ CX, AX, DX		// w1>>ŝ
+	MOVQ DX, c+56(FP)
+
+	CMPQ BX, $0
+	JLE X8a			// i <= 0
+
+	// i > 0
+L8:	MOVQ AX, DX		// w = w1
+	MOVQ -8(R8)(BX*8), AX	// w1 = x[i-1]
+	SHLQ CX, AX, DX		// w<<s | w1>>ŝ
+	MOVQ DX, (R10)(BX*8)	// z[i] = w<<s | w1>>ŝ
+	SUBQ $1, BX		// i--
+	JG L8			// i > 0
+
+	// i <= 0
+X8a:	SHLQ CX, AX		// w1<<s
+	MOVQ AX, (R10)		// z[0] = w1<<s
+	RET
+
+X8b:	MOVQ $0, c+56(FP)
+	RET
+
+
+// func shrVU(z, x []Word, s uint) (c Word)
+TEXT ·shrVU(SB),NOSPLIT,$0
+	MOVQ z_len+8(FP), R11
+	SUBQ $1, R11		// n--
+	JL X9b			// n < 0	(n <= 0)
+
+	// n > 0
+	MOVQ z+0(FP), R10
+	MOVQ x+24(FP), R8
+	MOVQ s+48(FP), CX
+	MOVQ (R8), AX		// w1 = x[0]
+	MOVQ $0, DX
+	SHRQ CX, AX, DX		// w1<<ŝ
+	MOVQ DX, c+56(FP)
+
+	MOVQ $0, BX		// i = 0
+	JMP E9
+
+	// i < n-1
+L9:	MOVQ AX, DX		// w = w1
+	MOVQ 8(R8)(BX*8), AX	// w1 = x[i+1]
+	SHRQ CX, AX, DX		// w>>s | w1<<ŝ
+	MOVQ DX, (R10)(BX*8)	// z[i] = w>>s | w1<<ŝ
+	ADDQ $1, BX		// i++
+
+E9:	CMPQ BX, R11
+	JL L9			// i < n-1
+
+	// i >= n-1
+X9a:	SHRQ CX, AX		// w1>>s
+	MOVQ AX, (R10)(R11*8)	// z[n-1] = w1>>s
+	RET
+
+X9b:	MOVQ $0, c+56(FP)
+	RET
+
+
+// func mulAddVWW(z, x []Word, y, r Word) (c Word)
+TEXT ·mulAddVWW(SB),NOSPLIT,$0
+	MOVQ z+0(FP), R10
+	MOVQ x+24(FP), R8
+	MOVQ y+48(FP), R9
+	MOVQ r+56(FP), CX	// c = r
+	MOVQ z_len+8(FP), R11
+	MOVQ $0, BX		// i = 0
+
+	CMPQ R11, $4
+	JL E5
+
+U5:	// i+4 <= n
+	// regular loop body unrolled 4x
+	MOVQ (0*8)(R8)(BX*8), AX
+	MULQ R9
+	ADDQ CX, AX
+	ADCQ $0, DX
+	MOVQ AX, (0*8)(R10)(BX*8)
+	MOVQ DX, CX
+	MOVQ (1*8)(R8)(BX*8), AX
+	MULQ R9
+	ADDQ CX, AX
+	ADCQ $0, DX
+	MOVQ AX, (1*8)(R10)(BX*8)
+	MOVQ DX, CX
+	MOVQ (2*8)(R8)(BX*8), AX
+	MULQ R9
+	ADDQ CX, AX
+	ADCQ $0, DX
+	MOVQ AX, (2*8)(R10)(BX*8)
+	MOVQ DX, CX
+	MOVQ (3*8)(R8)(BX*8), AX
+	MULQ R9
+	ADDQ CX, AX
+	ADCQ $0, DX
+	MOVQ AX, (3*8)(R10)(BX*8)
+	MOVQ DX, CX
+	ADDQ $4, BX		// i += 4
+
+	LEAQ 4(BX), DX
+	CMPQ DX, R11
+	JLE U5
+	JMP E5
+
+L5:	MOVQ (R8)(BX*8), AX
+	MULQ R9
+	ADDQ CX, AX
+	ADCQ $0, DX
+	MOVQ AX, (R10)(BX*8)
+	MOVQ DX, CX
+	ADDQ $1, BX		// i++
+
+E5:	CMPQ BX, R11		// i < n
+	JL L5
+
+	MOVQ CX, c+64(FP)
+	RET
+
+
+// func addMulVVW(z, x []Word, y Word) (c Word)
+TEXT ·addMulVVW(SB),NOSPLIT,$0
+	CMPB ·support_adx(SB), $1
+	JEQ adx
+	MOVQ z+0(FP), R10
+	MOVQ x+24(FP), R8
+	MOVQ y+48(FP), R9
+	MOVQ z_len+8(FP), R11
+	MOVQ $0, BX		// i = 0
+	MOVQ $0, CX		// c = 0
+	MOVQ R11, R12
+	ANDQ $-2, R12
+	CMPQ R11, $2
+	JAE A6
+	JMP E6
+
+A6:
+	MOVQ (R8)(BX*8), AX
+	MULQ R9
+	ADDQ (R10)(BX*8), AX
+	ADCQ $0, DX
+	ADDQ CX, AX
+	ADCQ $0, DX
+	MOVQ DX, CX
+	MOVQ AX, (R10)(BX*8)
+
+	MOVQ (8)(R8)(BX*8), AX
+	MULQ R9
+	ADDQ (8)(R10)(BX*8), AX
+	ADCQ $0, DX
+	ADDQ CX, AX
+	ADCQ $0, DX
+	MOVQ DX, CX
+	MOVQ AX, (8)(R10)(BX*8)
+
+	ADDQ $2, BX
+	CMPQ BX, R12
+	JL A6
+	JMP E6
+
+L6:	MOVQ (R8)(BX*8), AX
+	MULQ R9
+	ADDQ CX, AX
+	ADCQ $0, DX
+	ADDQ AX, (R10)(BX*8)
+	ADCQ $0, DX
+	MOVQ DX, CX
+	ADDQ $1, BX		// i++
+
+E6:	CMPQ BX, R11		// i < n
+	JL L6
+
+	MOVQ CX, c+56(FP)
+	RET
+
+adx:
+	MOVQ z_len+8(FP), R11
+	MOVQ z+0(FP), R10
+	MOVQ x+24(FP), R8
+	MOVQ y+48(FP), DX
+	MOVQ $0, BX   // i = 0
+	MOVQ $0, CX   // carry
+	CMPQ R11, $8
+	JAE  adx_loop_header
+	CMPQ BX, R11
+	JL adx_short
+	MOVQ CX, c+56(FP)
+	RET
+
+adx_loop_header:
+	MOVQ  R11, R13
+	ANDQ  $-8, R13
+adx_loop:
+	XORQ  R9, R9  // unset flags
+	MULXQ (R8), SI, DI
+	ADCXQ CX,SI
+	ADOXQ (R10), SI
+	MOVQ  SI,(R10)
+
+	MULXQ 8(R8), AX, CX
+	ADCXQ DI, AX
+	ADOXQ 8(R10), AX
+	MOVQ  AX, 8(R10)
+
+	MULXQ 16(R8), SI, DI
+	ADCXQ CX, SI
+	ADOXQ 16(R10), SI
+	MOVQ  SI, 16(R10)
+
+	MULXQ 24(R8), AX, CX
+	ADCXQ DI, AX
+	ADOXQ 24(R10), AX
+	MOVQ  AX, 24(R10)
+
+	MULXQ 32(R8), SI, DI
+	ADCXQ CX, SI
+	ADOXQ 32(R10), SI
+	MOVQ  SI, 32(R10)
+
+	MULXQ 40(R8), AX, CX
+	ADCXQ DI, AX
+	ADOXQ 40(R10), AX
+	MOVQ  AX, 40(R10)
+
+	MULXQ 48(R8), SI, DI
+	ADCXQ CX, SI
+	ADOXQ 48(R10), SI
+	MOVQ  SI, 48(R10)
+
+	MULXQ 56(R8), AX, CX
+	ADCXQ DI, AX
+	ADOXQ 56(R10), AX
+	MOVQ  AX, 56(R10)
+
+	ADCXQ R9, CX
+	ADOXQ R9, CX
+
+	ADDQ $64, R8
+	ADDQ $64, R10
+	ADDQ $8, BX
+
+	CMPQ BX, R13
+	JL adx_loop
+	MOVQ z+0(FP), R10
+	MOVQ x+24(FP), R8
+	CMPQ BX, R11
+	JL adx_short
+	MOVQ CX, c+56(FP)
+	RET
+
+adx_short:
+	MULXQ (R8)(BX*8), SI, DI
+	ADDQ CX, SI
+	ADCQ $0, DI
+	ADDQ SI, (R10)(BX*8)
+	ADCQ $0, DI
+	MOVQ DI, CX
+	ADDQ $1, BX		// i++
+
+	CMPQ BX, R11
+	JL adx_short
+
+	MOVQ CX, c+56(FP)
+	RET
+
+
+
diff --git a/contrib/go/_std_1.18/src/math/big/arith_decl.go b/contrib/go/_std_1.18/src/math/big/arith_decl.go
new file mode 100644
index 0000000000..eea3d6b325
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/arith_decl.go
@@ -0,0 +1,19 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !math_big_pure_go
+// +build !math_big_pure_go
+
+package big
+
+// implemented in arith_$GOARCH.s
+func mulWW(x, y Word) (z1, z0 Word)
+func addVV(z, x, y []Word) (c Word)
+func subVV(z, x, y []Word) (c Word)
+func addVW(z, x []Word, y Word) (c Word)
+func subVW(z, x []Word, y Word) (c Word)
+func shlVU(z, x []Word, s uint) (c Word)
+func shrVU(z, x []Word, s uint) (c Word)
+func mulAddVWW(z, x []Word, y, r Word) (c Word)
+func addMulVVW(z, x []Word, y Word) (c Word)
diff --git a/contrib/go/_std_1.18/src/math/big/decimal.go b/contrib/go/_std_1.18/src/math/big/decimal.go
new file mode 100644
index 0000000000..716f03bfa4
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/decimal.go
@@ -0,0 +1,270 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements multi-precision decimal numbers.
+// The implementation is for float to decimal conversion only;
+// not general purpose use.
+// The only operations are precise conversion from binary to
+// decimal and rounding.
+//
+// The key observation and some code (shr) is borrowed from
+// strconv/decimal.go: conversion of binary fractional values can be done
+// precisely in multi-precision decimal because 2 divides 10 (required for
+// >> of mantissa); but conversion of decimal floating-point values cannot
+// be done precisely in binary representation.
+//
+// In contrast to strconv/decimal.go, only right shift is implemented in
+// decimal format - left shift can be done precisely in binary format.
+
+package big
+
+// A decimal represents an unsigned floating-point number in decimal representation.
+// The value of a non-zero decimal d is d.mant * 10**d.exp with 0.1 <= d.mant < 1,
+// with the most-significant mantissa digit at index 0. For the zero decimal, the
+// mantissa length and exponent are 0.
+// The zero value for decimal represents a ready-to-use 0.0.
+type decimal struct {
+	mant []byte // mantissa ASCII digits, big-endian
+	exp  int    // exponent
+}
+
+// at returns the i'th mantissa digit, starting with the most significant digit at 0.
+func (d *decimal) at(i int) byte {
+	if 0 <= i && i < len(d.mant) {
+		return d.mant[i]
+	}
+	return '0'
+}
+
+// Maximum shift amount that can be done in one pass without overflow.
+// A Word has _W bits and (1<<maxShift - 1)*10 + 9 must fit into Word.
+const maxShift = _W - 4
+
+// TODO(gri) Since we know the desired decimal precision when converting
+// a floating-point number, we may be able to limit the number of decimal
+// digits that need to be computed by init by providing an additional
+// precision argument and keeping track of when a number was truncated early
+// (equivalent of "sticky bit" in binary rounding).
+
+// TODO(gri) Along the same lines, enforce some limit to shift magnitudes
+// to avoid "infinitely" long running conversions (until we run out of space).
+
+// Init initializes x to the decimal representation of m << shift (for
+// shift >= 0), or m >> -shift (for shift < 0).
+func (x *decimal) init(m nat, shift int) {
+	// special case 0
+	if len(m) == 0 {
+		x.mant = x.mant[:0]
+		x.exp = 0
+		return
+	}
+
+	// Optimization: If we need to shift right, first remove any trailing
+	// zero bits from m to reduce shift amount that needs to be done in
+	// decimal format (since that is likely slower).
+	if shift < 0 {
+		ntz := m.trailingZeroBits()
+		s := uint(-shift)
+		if s >= ntz {
+			s = ntz // shift at most ntz bits
+		}
+		m = nat(nil).shr(m, s)
+		shift += int(s)
+	}
+
+	// Do any shift left in binary representation.
+	if shift > 0 {
+		m = nat(nil).shl(m, uint(shift))
+		shift = 0
+	}
+
+	// Convert mantissa into decimal representation.
+	s := m.utoa(10)
+	n := len(s)
+	x.exp = n
+	// Trim trailing zeros; instead the exponent is tracking
+	// the decimal point independent of the number of digits.
+	for n > 0 && s[n-1] == '0' {
+		n--
+	}
+	x.mant = append(x.mant[:0], s[:n]...)
+
+	// Do any (remaining) shift right in decimal representation.
+	if shift < 0 {
+		for shift < -maxShift {
+			shr(x, maxShift)
+			shift += maxShift
+		}
+		shr(x, uint(-shift))
+	}
+}
+
+// shr implements x >> s, for s <= maxShift.
+func shr(x *decimal, s uint) {
+	// Division by 1<<s using shift-and-subtract algorithm.
+
+	// pick up enough leading digits to cover first shift
+	r := 0 // read index
+	var n Word
+	for n>>s == 0 && r < len(x.mant) {
+		ch := Word(x.mant[r])
+		r++
+		n = n*10 + ch - '0'
+	}
+	if n == 0 {
+		// x == 0; shouldn't get here, but handle anyway
+		x.mant = x.mant[:0]
+		return
+	}
+	for n>>s == 0 {
+		r++
+		n *= 10
+	}
+	x.exp += 1 - r
+
+	// read a digit, write a digit
+	w := 0 // write index
+	mask := Word(1)<<s - 1
+	for r < len(x.mant) {
+		ch := Word(x.mant[r])
+		r++
+		d := n >> s
+		n &= mask // n -= d << s
+		x.mant[w] = byte(d + '0')
+		w++
+		n = n*10 + ch - '0'
+	}
+
+	// write extra digits that still fit
+	for n > 0 && w < len(x.mant) {
+		d := n >> s
+		n &= mask
+		x.mant[w] = byte(d + '0')
+		w++
+		n = n * 10
+	}
+	x.mant = x.mant[:w] // the number may be shorter (e.g. 1024 >> 10)
+
+	// append additional digits that didn't fit
+	for n > 0 {
+		d := n >> s
+		n &= mask
+		x.mant = append(x.mant, byte(d+'0'))
+		n = n * 10
+	}
+
+	trim(x)
+}
+
+func (x *decimal) String() string {
+	if len(x.mant) == 0 {
+		return "0"
+	}
+
+	var buf []byte
+	switch {
+	case x.exp <= 0:
+		// 0.00ddd
+		buf = make([]byte, 0, 2+(-x.exp)+len(x.mant))
+		buf = append(buf, "0."...)
+		buf = appendZeros(buf, -x.exp)
+		buf = append(buf, x.mant...)
+
+	case /* 0 < */ x.exp < len(x.mant):
+		// dd.ddd
+		buf = make([]byte, 0, 1+len(x.mant))
+		buf = append(buf, x.mant[:x.exp]...)
+		buf = append(buf, '.')
+		buf = append(buf, x.mant[x.exp:]...)
+
+	default: // len(x.mant) <= x.exp
+		// ddd00
+		buf = make([]byte, 0, x.exp)
+		buf = append(buf, x.mant...)
+		buf = appendZeros(buf, x.exp-len(x.mant))
+	}
+
+	return string(buf)
+}
+
+// appendZeros appends n 0 digits to buf and returns buf.
+func appendZeros(buf []byte, n int) []byte {
+	for ; n > 0; n-- {
+		buf = append(buf, '0')
+	}
+	return buf
+}
+
+// shouldRoundUp reports if x should be rounded up
+// if shortened to n digits. n must be a valid index
+// for x.mant.
+func shouldRoundUp(x *decimal, n int) bool {
+	if x.mant[n] == '5' && n+1 == len(x.mant) {
+		// exactly halfway - round to even
+		return n > 0 && (x.mant[n-1]-'0')&1 != 0
+	}
+	// not halfway - digit tells all (x.mant has no trailing zeros)
+	return x.mant[n] >= '5'
+}
+
+// round sets x to (at most) n mantissa digits by rounding it
+// to the nearest even value with n (or fever) mantissa digits.
+// If n < 0, x remains unchanged.
+func (x *decimal) round(n int) {
+	if n < 0 || n >= len(x.mant) {
+		return // nothing to do
+	}
+
+	if shouldRoundUp(x, n) {
+		x.roundUp(n)
+	} else {
+		x.roundDown(n)
+	}
+}
+
+func (x *decimal) roundUp(n int) {
+	if n < 0 || n >= len(x.mant) {
+		return // nothing to do
+	}
+	// 0 <= n < len(x.mant)
+
+	// find first digit < '9'
+	for n > 0 && x.mant[n-1] >= '9' {
+		n--
+	}
+
+	if n == 0 {
+		// all digits are '9's => round up to '1' and update exponent
+		x.mant[0] = '1' // ok since len(x.mant) > n
+		x.mant = x.mant[:1]
+		x.exp++
+		return
+	}
+
+	// n > 0 && x.mant[n-1] < '9'
+	x.mant[n-1]++
+	x.mant = x.mant[:n]
+	// x already trimmed
+}
+
+func (x *decimal) roundDown(n int) {
+	if n < 0 || n >= len(x.mant) {
+		return // nothing to do
+	}
+	x.mant = x.mant[:n]
+	trim(x)
+}
+
+// trim cuts off any trailing zeros from x's mantissa;
+// they are meaningless for the value of x.
+func trim(x *decimal) {
+	i := len(x.mant)
+	for i > 0 && x.mant[i-1] == '0' {
+		i--
+	}
+	x.mant = x.mant[:i]
+	if i == 0 {
+		x.exp = 0
+	}
+}
diff --git a/contrib/go/_std_1.18/src/math/big/doc.go b/contrib/go/_std_1.18/src/math/big/doc.go
new file mode 100644
index 0000000000..65ed019b74
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/doc.go
@@ -0,0 +1,99 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package big implements arbitrary-precision arithmetic (big numbers).
+The following numeric types are supported:
+
+	Int    signed integers
+	Rat    rational numbers
+	Float  floating-point numbers
+
+The zero value for an Int, Rat, or Float correspond to 0. Thus, new
+values can be declared in the usual ways and denote 0 without further
+initialization:
+
+	var x Int        // &x is an *Int of value 0
+	var r = &Rat{}   // r is a *Rat of value 0
+	y := new(Float)  // y is a *Float of value 0
+
+Alternatively, new values can be allocated and initialized with factory
+functions of the form:
+
+	func NewT(v V) *T
+
+For instance, NewInt(x) returns an *Int set to the value of the int64
+argument x, NewRat(a, b) returns a *Rat set to the fraction a/b where
+a and b are int64 values, and NewFloat(f) returns a *Float initialized
+to the float64 argument f. More flexibility is provided with explicit
+setters, for instance:
+
+	var z1 Int
+	z1.SetUint64(123)                 // z1 := 123
+	z2 := new(Rat).SetFloat64(1.25)   // z2 := 5/4
+	z3 := new(Float).SetInt(z1)       // z3 := 123.0
+
+Setters, numeric operations and predicates are represented as methods of
+the form:
+
+	func (z *T) SetV(v V) *T          // z = v
+	func (z *T) Unary(x *T) *T        // z = unary x
+	func (z *T) Binary(x, y *T) *T    // z = x binary y
+	func (x *T) Pred() P              // p = pred(x)
+
+with T one of Int, Rat, or Float. For unary and binary operations, the
+result is the receiver (usually named z in that case; see below); if it
+is one of the operands x or y it may be safely overwritten (and its memory
+reused).
+
+Arithmetic expressions are typically written as a sequence of individual
+method calls, with each call corresponding to an operation. The receiver
+denotes the result and the method arguments are the operation's operands.
+For instance, given three *Int values a, b and c, the invocation
+
+	c.Add(a, b)
+
+computes the sum a + b and stores the result in c, overwriting whatever
+value was held in c before. Unless specified otherwise, operations permit
+aliasing of parameters, so it is perfectly ok to write
+
+	sum.Add(sum, x)
+
+to accumulate values x in a sum.
+
+(By always passing in a result value via the receiver, memory use can be
+much better controlled. Instead of having to allocate new memory for each
+result, an operation can reuse the space allocated for the result value,
+and overwrite that value with the new result in the process.)
+
+Notational convention: Incoming method parameters (including the receiver)
+are named consistently in the API to clarify their use. Incoming operands
+are usually named x, y, a, b, and so on, but never z. A parameter specifying
+the result is named z (typically the receiver).
+
+For instance, the arguments for (*Int).Add are named x and y, and because
+the receiver specifies the result destination, it is called z:
+
+	func (z *Int) Add(x, y *Int) *Int
+
+Methods of this form typically return the incoming receiver as well, to
+enable simple call chaining.
+
+Methods which don't require a result value to be passed in (for instance,
+Int.Sign), simply return the result. In this case, the receiver is typically
+the first operand, named x:
+
+	func (x *Int) Sign() int
+
+Various methods support conversions between strings and corresponding
+numeric values, and vice versa: *Int, *Rat, and *Float values implement
+the Stringer interface for a (default) string representation of the value,
+but also provide SetString methods to initialize a value from a string in
+a variety of supported formats (see the respective SetString documentation).
+
+Finally, *Int, *Rat, and *Float satisfy the fmt package's Scanner interface
+for scanning and (except for *Rat) the Formatter interface for formatted
+printing.
+*/
+package big
diff --git a/contrib/go/_std_1.18/src/math/big/float.go b/contrib/go/_std_1.18/src/math/big/float.go
new file mode 100644
index 0000000000..a8c91a6e54
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/float.go
@@ -0,0 +1,1732 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements multi-precision floating-point numbers.
+// Like in the GNU MPFR library (https://www.mpfr.org/), operands
+// can be of mixed precision. Unlike MPFR, the rounding mode is
+// not specified with each operation, but with each operand. The
+// rounding mode of the result operand determines the rounding
+// mode of an operation. This is a from-scratch implementation.
+
+package big
+
+import (
+	"fmt"
+	"math"
+	"math/bits"
+)
+
+const debugFloat = false // enable for debugging
+
+// A nonzero finite Float represents a multi-precision floating point number
+//
+//   sign × mantissa × 2**exponent
+//
+// with 0.5 <= mantissa < 1.0, and MinExp <= exponent <= MaxExp.
+// A Float may also be zero (+0, -0) or infinite (+Inf, -Inf).
+// All Floats are ordered, and the ordering of two Floats x and y
+// is defined by x.Cmp(y).
+//
+// Each Float value also has a precision, rounding mode, and accuracy.
+// The precision is the maximum number of mantissa bits available to
+// represent the value. The rounding mode specifies how a result should
+// be rounded to fit into the mantissa bits, and accuracy describes the
+// rounding error with respect to the exact result.
+//
+// Unless specified otherwise, all operations (including setters) that
+// specify a *Float variable for the result (usually via the receiver
+// with the exception of MantExp), round the numeric result according
+// to the precision and rounding mode of the result variable.
+//
+// If the provided result precision is 0 (see below), it is set to the
+// precision of the argument with the largest precision value before any
+// rounding takes place, and the rounding mode remains unchanged. Thus,
+// uninitialized Floats provided as result arguments will have their
+// precision set to a reasonable value determined by the operands, and
+// their mode is the zero value for RoundingMode (ToNearestEven).
+//
+// By setting the desired precision to 24 or 53 and using matching rounding
+// mode (typically ToNearestEven), Float operations produce the same results
+// as the corresponding float32 or float64 IEEE-754 arithmetic for operands
+// that correspond to normal (i.e., not denormal) float32 or float64 numbers.
+// Exponent underflow and overflow lead to a 0 or an Infinity for different
+// values than IEEE-754 because Float exponents have a much larger range.
+//
+// The zero (uninitialized) value for a Float is ready to use and represents
+// the number +0.0 exactly, with precision 0 and rounding mode ToNearestEven.
+//
+// Operations always take pointer arguments (*Float) rather
+// than Float values, and each unique Float value requires
+// its own unique *Float pointer. To "copy" a Float value,
+// an existing (or newly allocated) Float must be set to
+// a new value using the Float.Set method; shallow copies
+// of Floats are not supported and may lead to errors.
+type Float struct {
+	prec uint32
+	mode RoundingMode
+	acc  Accuracy
+	form form
+	neg  bool
+	mant nat
+	exp  int32
+}
+
+// An ErrNaN panic is raised by a Float operation that would lead to
+// a NaN under IEEE-754 rules. An ErrNaN implements the error interface.
+type ErrNaN struct {
+	msg string
+}
+
+func (err ErrNaN) Error() string {
+	return err.msg
+}
+
+// NewFloat allocates and returns a new Float set to x,
+// with precision 53 and rounding mode ToNearestEven.
+// NewFloat panics with ErrNaN if x is a NaN.
+func NewFloat(x float64) *Float {
+	if math.IsNaN(x) {
+		panic(ErrNaN{"NewFloat(NaN)"})
+	}
+	return new(Float).SetFloat64(x)
+}
+
+// Exponent and precision limits.
+const (
+	MaxExp  = math.MaxInt32  // largest supported exponent
+	MinExp  = math.MinInt32  // smallest supported exponent
+	MaxPrec = math.MaxUint32 // largest (theoretically) supported precision; likely memory-limited
+)
+
+// Internal representation: The mantissa bits x.mant of a nonzero finite
+// Float x are stored in a nat slice long enough to hold up to x.prec bits;
+// the slice may (but doesn't have to) be shorter if the mantissa contains
+// trailing 0 bits. x.mant is normalized if the msb of x.mant == 1 (i.e.,
+// the msb is shifted all the way "to the left"). Thus, if the mantissa has
+// trailing 0 bits or x.prec is not a multiple of the Word size _W,
+// x.mant[0] has trailing zero bits. The msb of the mantissa corresponds
+// to the value 0.5; the exponent x.exp shifts the binary point as needed.
+//
+// A zero or non-finite Float x ignores x.mant and x.exp.
+//
+// x                 form      neg      mant         exp
+// ----------------------------------------------------------
+// ±0                zero      sign     -            -
+// 0 < |x| < +Inf    finite    sign     mantissa     exponent
+// ±Inf              inf       sign     -            -
+
+// A form value describes the internal representation.
+type form byte
+
+// The form value order is relevant - do not change!
+const (
+	zero form = iota
+	finite
+	inf
+)
+
+// RoundingMode determines how a Float value is rounded to the
+// desired precision. Rounding may change the Float value; the
+// rounding error is described by the Float's Accuracy.
+type RoundingMode byte
+
+// These constants define supported rounding modes.
+const (
+	ToNearestEven RoundingMode = iota // == IEEE 754-2008 roundTiesToEven
+	ToNearestAway                     // == IEEE 754-2008 roundTiesToAway
+	ToZero                            // == IEEE 754-2008 roundTowardZero
+	AwayFromZero                      // no IEEE 754-2008 equivalent
+	ToNegativeInf                     // == IEEE 754-2008 roundTowardNegative
+	ToPositiveInf                     // == IEEE 754-2008 roundTowardPositive
+)
+
+//go:generate stringer -type=RoundingMode
+
+// Accuracy describes the rounding error produced by the most recent
+// operation that generated a Float value, relative to the exact value.
+type Accuracy int8
+
+// Constants describing the Accuracy of a Float.
+const (
+	Below Accuracy = -1
+	Exact Accuracy = 0
+	Above Accuracy = +1
+)
+
+//go:generate stringer -type=Accuracy
+
+// SetPrec sets z's precision to prec and returns the (possibly) rounded
+// value of z. Rounding occurs according to z's rounding mode if the mantissa
+// cannot be represented in prec bits without loss of precision.
+// SetPrec(0) maps all finite values to ±0; infinite values remain unchanged.
+// If prec > MaxPrec, it is set to MaxPrec.
+func (z *Float) SetPrec(prec uint) *Float {
+	z.acc = Exact // optimistically assume no rounding is needed
+
+	// special case
+	if prec == 0 {
+		z.prec = 0
+		if z.form == finite {
+			// truncate z to 0
+			z.acc = makeAcc(z.neg)
+			z.form = zero
+		}
+		return z
+	}
+
+	// general case
+	if prec > MaxPrec {
+		prec = MaxPrec
+	}
+	old := z.prec
+	z.prec = uint32(prec)
+	if z.prec < old {
+		z.round(0)
+	}
+	return z
+}
+
+func makeAcc(above bool) Accuracy {
+	if above {
+		return Above
+	}
+	return Below
+}
+
+// SetMode sets z's rounding mode to mode and returns an exact z.
+// z remains unchanged otherwise.
+// z.SetMode(z.Mode()) is a cheap way to set z's accuracy to Exact.
+func (z *Float) SetMode(mode RoundingMode) *Float {
+	z.mode = mode
+	z.acc = Exact
+	return z
+}
+
+// Prec returns the mantissa precision of x in bits.
+// The result may be 0 for |x| == 0 and |x| == Inf.
+func (x *Float) Prec() uint {
+	return uint(x.prec)
+}
+
+// MinPrec returns the minimum precision required to represent x exactly
+// (i.e., the smallest prec before x.SetPrec(prec) would start rounding x).
+// The result is 0 for |x| == 0 and |x| == Inf.
+func (x *Float) MinPrec() uint {
+	if x.form != finite {
+		return 0
+	}
+	return uint(len(x.mant))*_W - x.mant.trailingZeroBits()
+}
+
+// Mode returns the rounding mode of x.
+func (x *Float) Mode() RoundingMode {
+	return x.mode
+}
+
+// Acc returns the accuracy of x produced by the most recent
+// operation, unless explicitly documented otherwise by that
+// operation.
+func (x *Float) Acc() Accuracy {
+	return x.acc
+}
+
+// Sign returns:
+//
+//	-1 if x <   0
+//	 0 if x is ±0
+//	+1 if x >   0
+//
+func (x *Float) Sign() int {
+	if debugFloat {
+		x.validate()
+	}
+	if x.form == zero {
+		return 0
+	}
+	if x.neg {
+		return -1
+	}
+	return 1
+}
+
+// MantExp breaks x into its mantissa and exponent components
+// and returns the exponent. If a non-nil mant argument is
+// provided its value is set to the mantissa of x, with the
+// same precision and rounding mode as x. The components
+// satisfy x == mant × 2**exp, with 0.5 <= |mant| < 1.0.
+// Calling MantExp with a nil argument is an efficient way to
+// get the exponent of the receiver.
+//
+// Special cases are:
+//
+//	(  ±0).MantExp(mant) = 0, with mant set to   ±0
+//	(±Inf).MantExp(mant) = 0, with mant set to ±Inf
+//
+// x and mant may be the same in which case x is set to its
+// mantissa value.
+func (x *Float) MantExp(mant *Float) (exp int) {
+	if debugFloat {
+		x.validate()
+	}
+	if x.form == finite {
+		exp = int(x.exp)
+	}
+	if mant != nil {
+		mant.Copy(x)
+		if mant.form == finite {
+			mant.exp = 0
+		}
+	}
+	return
+}
+
+func (z *Float) setExpAndRound(exp int64, sbit uint) {
+	if exp < MinExp {
+		// underflow
+		z.acc = makeAcc(z.neg)
+		z.form = zero
+		return
+	}
+
+	if exp > MaxExp {
+		// overflow
+		z.acc = makeAcc(!z.neg)
+		z.form = inf
+		return
+	}
+
+	z.form = finite
+	z.exp = int32(exp)
+	z.round(sbit)
+}
+
+// SetMantExp sets z to mant × 2**exp and returns z.
+// The result z has the same precision and rounding mode
+// as mant. SetMantExp is an inverse of MantExp but does
+// not require 0.5 <= |mant| < 1.0. Specifically, for a
+// given x of type *Float, SetMantExp relates to MantExp
+// as follows:
+//
+//	mant := new(Float)
+//	new(Float).SetMantExp(mant, x.MantExp(mant)).Cmp(x) == 0
+//
+// Special cases are:
+//
+//	z.SetMantExp(  ±0, exp) =   ±0
+//	z.SetMantExp(±Inf, exp) = ±Inf
+//
+// z and mant may be the same in which case z's exponent
+// is set to exp.
+func (z *Float) SetMantExp(mant *Float, exp int) *Float {
+	if debugFloat {
+		z.validate()
+		mant.validate()
+	}
+	z.Copy(mant)
+
+	if z.form == finite {
+		// 0 < |mant| < +Inf
+		z.setExpAndRound(int64(z.exp)+int64(exp), 0)
+	}
+	return z
+}
+
+// Signbit reports whether x is negative or negative zero.
+func (x *Float) Signbit() bool {
+	return x.neg
+}
+
+// IsInf reports whether x is +Inf or -Inf.
+func (x *Float) IsInf() bool {
+	return x.form == inf
+}
+
+// IsInt reports whether x is an integer.
+// ±Inf values are not integers.
+func (x *Float) IsInt() bool {
+	if debugFloat {
+		x.validate()
+	}
+	// special cases
+	if x.form != finite {
+		return x.form == zero
+	}
+	// x.form == finite
+	if x.exp <= 0 {
+		return false
+	}
+	// x.exp > 0
+	return x.prec <= uint32(x.exp) || x.MinPrec() <= uint(x.exp) // not enough bits for fractional mantissa
+}
+
+// debugging support
+func (x *Float) validate() {
+	if !debugFloat {
+		// avoid performance bugs
+		panic("validate called but debugFloat is not set")
+	}
+	if x.form != finite {
+		return
+	}
+	m := len(x.mant)
+	if m == 0 {
+		panic("nonzero finite number with empty mantissa")
+	}
+	const msb = 1 << (_W - 1)
+	if x.mant[m-1]&msb == 0 {
+		panic(fmt.Sprintf("msb not set in last word %#x of %s", x.mant[m-1], x.Text('p', 0)))
+	}
+	if x.prec == 0 {
+		panic("zero precision finite number")
+	}
+}
+
+// round rounds z according to z.mode to z.prec bits and sets z.acc accordingly.
+// sbit must be 0 or 1 and summarizes any "sticky bit" information one might
+// have before calling round. z's mantissa must be normalized (with the msb set)
+// or empty.
+//
+// CAUTION: The rounding modes ToNegativeInf, ToPositiveInf are affected by the
+// sign of z. For correct rounding, the sign of z must be set correctly before
+// calling round.
+func (z *Float) round(sbit uint) {
+	if debugFloat {
+		z.validate()
+	}
+
+	z.acc = Exact
+	if z.form != finite {
+		// ±0 or ±Inf => nothing left to do
+		return
+	}
+	// z.form == finite && len(z.mant) > 0
+	// m > 0 implies z.prec > 0 (checked by validate)
+
+	m := uint32(len(z.mant)) // present mantissa length in words
+	bits := m * _W           // present mantissa bits; bits > 0
+	if bits <= z.prec {
+		// mantissa fits => nothing to do
+		return
+	}
+	// bits > z.prec
+
+	// Rounding is based on two bits: the rounding bit (rbit) and the
+	// sticky bit (sbit). The rbit is the bit immediately before the
+	// z.prec leading mantissa bits (the "0.5"). The sbit is set if any
+	// of the bits before the rbit are set (the "0.25", "0.125", etc.):
+	//
+	//   rbit  sbit  => "fractional part"
+	//
+	//   0     0        == 0
+	//   0     1        >  0  , < 0.5
+	//   1     0        == 0.5
+	//   1     1        >  0.5, < 1.0
+
+	// bits > z.prec: mantissa too large => round
+	r := uint(bits - z.prec - 1) // rounding bit position; r >= 0
+	rbit := z.mant.bit(r) & 1    // rounding bit; be safe and ensure it's a single bit
+	// The sticky bit is only needed for rounding ToNearestEven
+	// or when the rounding bit is zero. Avoid computation otherwise.
+	if sbit == 0 && (rbit == 0 || z.mode == ToNearestEven) {
+		sbit = z.mant.sticky(r)
+	}
+	sbit &= 1 // be safe and ensure it's a single bit
+
+	// cut off extra words
+	n := (z.prec + (_W - 1)) / _W // mantissa length in words for desired precision
+	if m > n {
+		copy(z.mant, z.mant[m-n:]) // move n last words to front
+		z.mant = z.mant[:n]
+	}
+
+	// determine number of trailing zero bits (ntz) and compute lsb mask of mantissa's least-significant word
+	ntz := n*_W - z.prec // 0 <= ntz < _W
+	lsb := Word(1) << ntz
+
+	// round if result is inexact
+	if rbit|sbit != 0 {
+		// Make rounding decision: The result mantissa is truncated ("rounded down")
+		// by default. Decide if we need to increment, or "round up", the (unsigned)
+		// mantissa.
+		inc := false
+		switch z.mode {
+		case ToNegativeInf:
+			inc = z.neg
+		case ToZero:
+			// nothing to do
+		case ToNearestEven:
+			inc = rbit != 0 && (sbit != 0 || z.mant[0]&lsb != 0)
+		case ToNearestAway:
+			inc = rbit != 0
+		case AwayFromZero:
+			inc = true
+		case ToPositiveInf:
+			inc = !z.neg
+		default:
+			panic("unreachable")
+		}
+
+		// A positive result (!z.neg) is Above the exact result if we increment,
+		// and it's Below if we truncate (Exact results require no rounding).
+		// For a negative result (z.neg) it is exactly the opposite.
+		z.acc = makeAcc(inc != z.neg)
+
+		if inc {
+			// add 1 to mantissa
+			if addVW(z.mant, z.mant, lsb) != 0 {
+				// mantissa overflow => adjust exponent
+				if z.exp >= MaxExp {
+					// exponent overflow
+					z.form = inf
+					return
+				}
+				z.exp++
+				// adjust mantissa: divide by 2 to compensate for exponent adjustment
+				shrVU(z.mant, z.mant, 1)
+				// set msb == carry == 1 from the mantissa overflow above
+				const msb = 1 << (_W - 1)
+				z.mant[n-1] |= msb
+			}
+		}
+	}
+
+	// zero out trailing bits in least-significant word
+	z.mant[0] &^= lsb - 1
+
+	if debugFloat {
+		z.validate()
+	}
+}
+
+func (z *Float) setBits64(neg bool, x uint64) *Float {
+	if z.prec == 0 {
+		z.prec = 64
+	}
+	z.acc = Exact
+	z.neg = neg
+	if x == 0 {
+		z.form = zero
+		return z
+	}
+	// x != 0
+	z.form = finite
+	s := bits.LeadingZeros64(x)
+	z.mant = z.mant.setUint64(x << uint(s))
+	z.exp = int32(64 - s) // always fits
+	if z.prec < 64 {
+		z.round(0)
+	}
+	return z
+}
+
+// SetUint64 sets z to the (possibly rounded) value of x and returns z.
+// If z's precision is 0, it is changed to 64 (and rounding will have
+// no effect).
+func (z *Float) SetUint64(x uint64) *Float {
+	return z.setBits64(false, x)
+}
+
+// SetInt64 sets z to the (possibly rounded) value of x and returns z.
+// If z's precision is 0, it is changed to 64 (and rounding will have
+// no effect).
+func (z *Float) SetInt64(x int64) *Float {
+	u := x
+	if u < 0 {
+		u = -u
+	}
+	// We cannot simply call z.SetUint64(uint64(u)) and change
+	// the sign afterwards because the sign affects rounding.
+	return z.setBits64(x < 0, uint64(u))
+}
+
+// SetFloat64 sets z to the (possibly rounded) value of x and returns z.
+// If z's precision is 0, it is changed to 53 (and rounding will have
+// no effect). SetFloat64 panics with ErrNaN if x is a NaN.
+func (z *Float) SetFloat64(x float64) *Float {
+	if z.prec == 0 {
+		z.prec = 53
+	}
+	if math.IsNaN(x) {
+		panic(ErrNaN{"Float.SetFloat64(NaN)"})
+	}
+	z.acc = Exact
+	z.neg = math.Signbit(x) // handle -0, -Inf correctly
+	if x == 0 {
+		z.form = zero
+		return z
+	}
+	if math.IsInf(x, 0) {
+		z.form = inf
+		return z
+	}
+	// normalized x != 0
+	z.form = finite
+	fmant, exp := math.Frexp(x) // get normalized mantissa
+	z.mant = z.mant.setUint64(1<<63 | math.Float64bits(fmant)<<11)
+	z.exp = int32(exp) // always fits
+	if z.prec < 53 {
+		z.round(0)
+	}
+	return z
+}
+
+// fnorm normalizes mantissa m by shifting it to the left
+// such that the msb of the most-significant word (msw) is 1.
+// It returns the shift amount. It assumes that len(m) != 0.
+func fnorm(m nat) int64 {
+	if debugFloat && (len(m) == 0 || m[len(m)-1] == 0) {
+		panic("msw of mantissa is 0")
+	}
+	s := nlz(m[len(m)-1])
+	if s > 0 {
+		c := shlVU(m, m, s)
+		if debugFloat && c != 0 {
+			panic("nlz or shlVU incorrect")
+		}
+	}
+	return int64(s)
+}
+
+// SetInt sets z to the (possibly rounded) value of x and returns z.
+// If z's precision is 0, it is changed to the larger of x.BitLen()
+// or 64 (and rounding will have no effect).
+func (z *Float) SetInt(x *Int) *Float {
+	// TODO(gri) can be more efficient if z.prec > 0
+	// but small compared to the size of x, or if there
+	// are many trailing 0's.
+	bits := uint32(x.BitLen())
+	if z.prec == 0 {
+		z.prec = umax32(bits, 64)
+	}
+	z.acc = Exact
+	z.neg = x.neg
+	if len(x.abs) == 0 {
+		z.form = zero
+		return z
+	}
+	// x != 0
+	z.mant = z.mant.set(x.abs)
+	fnorm(z.mant)
+	z.setExpAndRound(int64(bits), 0)
+	return z
+}
+
+// SetRat sets z to the (possibly rounded) value of x and returns z.
+// If z's precision is 0, it is changed to the largest of a.BitLen(),
+// b.BitLen(), or 64; with x = a/b.
+func (z *Float) SetRat(x *Rat) *Float {
+	if x.IsInt() {
+		return z.SetInt(x.Num())
+	}
+	var a, b Float
+	a.SetInt(x.Num())
+	b.SetInt(x.Denom())
+	if z.prec == 0 {
+		z.prec = umax32(a.prec, b.prec)
+	}
+	return z.Quo(&a, &b)
+}
+
+// SetInf sets z to the infinite Float -Inf if signbit is
+// set, or +Inf if signbit is not set, and returns z. The
+// precision of z is unchanged and the result is always
+// Exact.
+func (z *Float) SetInf(signbit bool) *Float {
+	z.acc = Exact
+	z.form = inf
+	z.neg = signbit
+	return z
+}
+
+// Set sets z to the (possibly rounded) value of x and returns z.
+// If z's precision is 0, it is changed to the precision of x
+// before setting z (and rounding will have no effect).
+// Rounding is performed according to z's precision and rounding
+// mode; and z's accuracy reports the result error relative to the
+// exact (not rounded) result.
+func (z *Float) Set(x *Float) *Float {
+	if debugFloat {
+		x.validate()
+	}
+	z.acc = Exact
+	if z != x {
+		z.form = x.form
+		z.neg = x.neg
+		if x.form == finite {
+			z.exp = x.exp
+			z.mant = z.mant.set(x.mant)
+		}
+		if z.prec == 0 {
+			z.prec = x.prec
+		} else if z.prec < x.prec {
+			z.round(0)
+		}
+	}
+	return z
+}
+
+// Copy sets z to x, with the same precision, rounding mode, and
+// accuracy as x, and returns z. x is not changed even if z and
+// x are the same.
+func (z *Float) Copy(x *Float) *Float {
+	if debugFloat {
+		x.validate()
+	}
+	if z != x {
+		z.prec = x.prec
+		z.mode = x.mode
+		z.acc = x.acc
+		z.form = x.form
+		z.neg = x.neg
+		if z.form == finite {
+			z.mant = z.mant.set(x.mant)
+			z.exp = x.exp
+		}
+	}
+	return z
+}
+
+// msb32 returns the 32 most significant bits of x.
+func msb32(x nat) uint32 {
+	i := len(x) - 1
+	if i < 0 {
+		return 0
+	}
+	if debugFloat && x[i]&(1<<(_W-1)) == 0 {
+		panic("x not normalized")
+	}
+	switch _W {
+	case 32:
+		return uint32(x[i])
+	case 64:
+		return uint32(x[i] >> 32)
+	}
+	panic("unreachable")
+}
+
+// msb64 returns the 64 most significant bits of x.
+func msb64(x nat) uint64 {
+	i := len(x) - 1
+	if i < 0 {
+		return 0
+	}
+	if debugFloat && x[i]&(1<<(_W-1)) == 0 {
+		panic("x not normalized")
+	}
+	switch _W {
+	case 32:
+		v := uint64(x[i]) << 32
+		if i > 0 {
+			v |= uint64(x[i-1])
+		}
+		return v
+	case 64:
+		return uint64(x[i])
+	}
+	panic("unreachable")
+}
+
+// Uint64 returns the unsigned integer resulting from truncating x
+// towards zero. If 0 <= x <= math.MaxUint64, the result is Exact
+// if x is an integer and Below otherwise.
+// The result is (0, Above) for x < 0, and (math.MaxUint64, Below)
+// for x > math.MaxUint64.
+func (x *Float) Uint64() (uint64, Accuracy) {
+	if debugFloat {
+		x.validate()
+	}
+
+	switch x.form {
+	case finite:
+		if x.neg {
+			return 0, Above
+		}
+		// 0 < x < +Inf
+		if x.exp <= 0 {
+			// 0 < x < 1
+			return 0, Below
+		}
+		// 1 <= x < Inf
+		if x.exp <= 64 {
+			// u = trunc(x) fits into a uint64
+			u := msb64(x.mant) >> (64 - uint32(x.exp))
+			if x.MinPrec() <= 64 {
+				return u, Exact
+			}
+			return u, Below // x truncated
+		}
+		// x too large
+		return math.MaxUint64, Below
+
+	case zero:
+		return 0, Exact
+
+	case inf:
+		if x.neg {
+			return 0, Above
+		}
+		return math.MaxUint64, Below
+	}
+
+	panic("unreachable")
+}
+
+// Int64 returns the integer resulting from truncating x towards zero.
+// If math.MinInt64 <= x <= math.MaxInt64, the result is Exact if x is
+// an integer, and Above (x < 0) or Below (x > 0) otherwise.
+// The result is (math.MinInt64, Above) for x < math.MinInt64,
+// and (math.MaxInt64, Below) for x > math.MaxInt64.
+func (x *Float) Int64() (int64, Accuracy) {
+	if debugFloat {
+		x.validate()
+	}
+
+	switch x.form {
+	case finite:
+		// 0 < |x| < +Inf
+		acc := makeAcc(x.neg)
+		if x.exp <= 0 {
+			// 0 < |x| < 1
+			return 0, acc
+		}
+		// x.exp > 0
+
+		// 1 <= |x| < +Inf
+		if x.exp <= 63 {
+			// i = trunc(x) fits into an int64 (excluding math.MinInt64)
+			i := int64(msb64(x.mant) >> (64 - uint32(x.exp)))
+			if x.neg {
+				i = -i
+			}
+			if x.MinPrec() <= uint(x.exp) {
+				return i, Exact
+			}
+			return i, acc // x truncated
+		}
+		if x.neg {
+			// check for special case x == math.MinInt64 (i.e., x == -(0.5 << 64))
+			if x.exp == 64 && x.MinPrec() == 1 {
+				acc = Exact
+			}
+			return math.MinInt64, acc
+		}
+		// x too large
+		return math.MaxInt64, Below
+
+	case zero:
+		return 0, Exact
+
+	case inf:
+		if x.neg {
+			return math.MinInt64, Above
+		}
+		return math.MaxInt64, Below
+	}
+
+	panic("unreachable")
+}
+
+// Float32 returns the float32 value nearest to x. If x is too small to be
+// represented by a float32 (|x| < math.SmallestNonzeroFloat32), the result
+// is (0, Below) or (-0, Above), respectively, depending on the sign of x.
+// If x is too large to be represented by a float32 (|x| > math.MaxFloat32),
+// the result is (+Inf, Above) or (-Inf, Below), depending on the sign of x.
+func (x *Float) Float32() (float32, Accuracy) {
+	if debugFloat {
+		x.validate()
+	}
+
+	switch x.form {
+	case finite:
+		// 0 < |x| < +Inf
+
+		const (
+			fbits = 32                //        float size
+			mbits = 23                //        mantissa size (excluding implicit msb)
+			ebits = fbits - mbits - 1 //     8  exponent size
+			bias  = 1<<(ebits-1) - 1  //   127  exponent bias
+			dmin  = 1 - bias - mbits  //  -149  smallest unbiased exponent (denormal)
+			emin  = 1 - bias          //  -126  smallest unbiased exponent (normal)
+			emax  = bias              //   127  largest unbiased exponent (normal)
+		)
+
+		// Float mantissa m is 0.5 <= m < 1.0; compute exponent e for float32 mantissa.
+		e := x.exp - 1 // exponent for normal mantissa m with 1.0 <= m < 2.0
+
+		// Compute precision p for float32 mantissa.
+		// If the exponent is too small, we have a denormal number before
+		// rounding and fewer than p mantissa bits of precision available
+		// (the exponent remains fixed but the mantissa gets shifted right).
+		p := mbits + 1 // precision of normal float
+		if e < emin {
+			// recompute precision
+			p = mbits + 1 - emin + int(e)
+			// If p == 0, the mantissa of x is shifted so much to the right
+			// that its msb falls immediately to the right of the float32
+			// mantissa space. In other words, if the smallest denormal is
+			// considered "1.0", for p == 0, the mantissa value m is >= 0.5.
+			// If m > 0.5, it is rounded up to 1.0; i.e., the smallest denormal.
+			// If m == 0.5, it is rounded down to even, i.e., 0.0.
+			// If p < 0, the mantissa value m is <= "0.25" which is never rounded up.
+			if p < 0 /* m <= 0.25 */ || p == 0 && x.mant.sticky(uint(len(x.mant))*_W-1) == 0 /* m == 0.5 */ {
+				// underflow to ±0
+				if x.neg {
+					var z float32
+					return -z, Above
+				}
+				return 0.0, Below
+			}
+			// otherwise, round up
+			// We handle p == 0 explicitly because it's easy and because
+			// Float.round doesn't support rounding to 0 bits of precision.
+			if p == 0 {
+				if x.neg {
+					return -math.SmallestNonzeroFloat32, Below
+				}
+				return math.SmallestNonzeroFloat32, Above
+			}
+		}
+		// p > 0
+
+		// round
+		var r Float
+		r.prec = uint32(p)
+		r.Set(x)
+		e = r.exp - 1
+
+		// Rounding may have caused r to overflow to ±Inf
+		// (rounding never causes underflows to 0).
+		// If the exponent is too large, also overflow to ±Inf.
+		if r.form == inf || e > emax {
+			// overflow
+			if x.neg {
+				return float32(math.Inf(-1)), Below
+			}
+			return float32(math.Inf(+1)), Above
+		}
+		// e <= emax
+
+		// Determine sign, biased exponent, and mantissa.
+		var sign, bexp, mant uint32
+		if x.neg {
+			sign = 1 << (fbits - 1)
+		}
+
+		// Rounding may have caused a denormal number to
+		// become normal. Check again.
+		if e < emin {
+			// denormal number: recompute precision
+			// Since rounding may have at best increased precision
+			// and we have eliminated p <= 0 early, we know p > 0.
+			// bexp == 0 for denormals
+			p = mbits + 1 - emin + int(e)
+			mant = msb32(r.mant) >> uint(fbits-p)
+		} else {
+			// normal number: emin <= e <= emax
+			bexp = uint32(e+bias) << mbits
+			mant = msb32(r.mant) >> ebits & (1<<mbits - 1) // cut off msb (implicit 1 bit)
+		}
+
+		return math.Float32frombits(sign | bexp | mant), r.acc
+
+	case zero:
+		if x.neg {
+			var z float32
+			return -z, Exact
+		}
+		return 0.0, Exact
+
+	case inf:
+		if x.neg {
+			return float32(math.Inf(-1)), Exact
+		}
+		return float32(math.Inf(+1)), Exact
+	}
+
+	panic("unreachable")
+}
+
+// Float64 returns the float64 value nearest to x. If x is too small to be
+// represented by a float64 (|x| < math.SmallestNonzeroFloat64), the result
+// is (0, Below) or (-0, Above), respectively, depending on the sign of x.
+// If x is too large to be represented by a float64 (|x| > math.MaxFloat64),
+// the result is (+Inf, Above) or (-Inf, Below), depending on the sign of x.
+func (x *Float) Float64() (float64, Accuracy) {
+	if debugFloat {
+		x.validate()
+	}
+
+	switch x.form {
+	case finite:
+		// 0 < |x| < +Inf
+
+		const (
+			fbits = 64                //        float size
+			mbits = 52                //        mantissa size (excluding implicit msb)
+			ebits = fbits - mbits - 1 //    11  exponent size
+			bias  = 1<<(ebits-1) - 1  //  1023  exponent bias
+			dmin  = 1 - bias - mbits  // -1074  smallest unbiased exponent (denormal)
+			emin  = 1 - bias          // -1022  smallest unbiased exponent (normal)
+			emax  = bias              //  1023  largest unbiased exponent (normal)
+		)
+
+		// Float mantissa m is 0.5 <= m < 1.0; compute exponent e for float64 mantissa.
+		e := x.exp - 1 // exponent for normal mantissa m with 1.0 <= m < 2.0
+
+		// Compute precision p for float64 mantissa.
+		// If the exponent is too small, we have a denormal number before
+		// rounding and fewer than p mantissa bits of precision available
+		// (the exponent remains fixed but the mantissa gets shifted right).
+		p := mbits + 1 // precision of normal float
+		if e < emin {
+			// recompute precision
+			p = mbits + 1 - emin + int(e)
+			// If p == 0, the mantissa of x is shifted so much to the right
+			// that its msb falls immediately to the right of the float64
+			// mantissa space. In other words, if the smallest denormal is
+			// considered "1.0", for p == 0, the mantissa value m is >= 0.5.
+			// If m > 0.5, it is rounded up to 1.0; i.e., the smallest denormal.
+			// If m == 0.5, it is rounded down to even, i.e., 0.0.
+			// If p < 0, the mantissa value m is <= "0.25" which is never rounded up.
+			if p < 0 /* m <= 0.25 */ || p == 0 && x.mant.sticky(uint(len(x.mant))*_W-1) == 0 /* m == 0.5 */ {
+				// underflow to ±0
+				if x.neg {
+					var z float64
+					return -z, Above
+				}
+				return 0.0, Below
+			}
+			// otherwise, round up
+			// We handle p == 0 explicitly because it's easy and because
+			// Float.round doesn't support rounding to 0 bits of precision.
+			if p == 0 {
+				if x.neg {
+					return -math.SmallestNonzeroFloat64, Below
+				}
+				return math.SmallestNonzeroFloat64, Above
+			}
+		}
+		// p > 0
+
+		// round
+		var r Float
+		r.prec = uint32(p)
+		r.Set(x)
+		e = r.exp - 1
+
+		// Rounding may have caused r to overflow to ±Inf
+		// (rounding never causes underflows to 0).
+		// If the exponent is too large, also overflow to ±Inf.
+		if r.form == inf || e > emax {
+			// overflow
+			if x.neg {
+				return math.Inf(-1), Below
+			}
+			return math.Inf(+1), Above
+		}
+		// e <= emax
+
+		// Determine sign, biased exponent, and mantissa.
+		var sign, bexp, mant uint64
+		if x.neg {
+			sign = 1 << (fbits - 1)
+		}
+
+		// Rounding may have caused a denormal number to
+		// become normal. Check again.
+		if e < emin {
+			// denormal number: recompute precision
+			// Since rounding may have at best increased precision
+			// and we have eliminated p <= 0 early, we know p > 0.
+			// bexp == 0 for denormals
+			p = mbits + 1 - emin + int(e)
+			mant = msb64(r.mant) >> uint(fbits-p)
+		} else {
+			// normal number: emin <= e <= emax
+			bexp = uint64(e+bias) << mbits
+			mant = msb64(r.mant) >> ebits & (1<<mbits - 1) // cut off msb (implicit 1 bit)
+		}
+
+		return math.Float64frombits(sign | bexp | mant), r.acc
+
+	case zero:
+		if x.neg {
+			var z float64
+			return -z, Exact
+		}
+		return 0.0, Exact
+
+	case inf:
+		if x.neg {
+			return math.Inf(-1), Exact
+		}
+		return math.Inf(+1), Exact
+	}
+
+	panic("unreachable")
+}
+
+// Int returns the result of truncating x towards zero;
+// or nil if x is an infinity.
+// The result is Exact if x.IsInt(); otherwise it is Below
+// for x > 0, and Above for x < 0.
+// If a non-nil *Int argument z is provided, Int stores
+// the result in z instead of allocating a new Int.
+func (x *Float) Int(z *Int) (*Int, Accuracy) {
+	if debugFloat {
+		x.validate()
+	}
+
+	if z == nil && x.form <= finite {
+		z = new(Int)
+	}
+
+	switch x.form {
+	case finite:
+		// 0 < |x| < +Inf
+		acc := makeAcc(x.neg)
+		if x.exp <= 0 {
+			// 0 < |x| < 1
+			return z.SetInt64(0), acc
+		}
+		// x.exp > 0
+
+		// 1 <= |x| < +Inf
+		// determine minimum required precision for x
+		allBits := uint(len(x.mant)) * _W
+		exp := uint(x.exp)
+		if x.MinPrec() <= exp {
+			acc = Exact
+		}
+		// shift mantissa as needed
+		if z == nil {
+			z = new(Int)
+		}
+		z.neg = x.neg
+		switch {
+		case exp > allBits:
+			z.abs = z.abs.shl(x.mant, exp-allBits)
+		default:
+			z.abs = z.abs.set(x.mant)
+		case exp < allBits:
+			z.abs = z.abs.shr(x.mant, allBits-exp)
+		}
+		return z, acc
+
+	case zero:
+		return z.SetInt64(0), Exact
+
+	case inf:
+		return nil, makeAcc(x.neg)
+	}
+
+	panic("unreachable")
+}
+
+// Rat returns the rational number corresponding to x;
+// or nil if x is an infinity.
+// The result is Exact if x is not an Inf.
+// If a non-nil *Rat argument z is provided, Rat stores
+// the result in z instead of allocating a new Rat.
+func (x *Float) Rat(z *Rat) (*Rat, Accuracy) {
+	if debugFloat {
+		x.validate()
+	}
+
+	if z == nil && x.form <= finite {
+		z = new(Rat)
+	}
+
+	switch x.form {
+	case finite:
+		// 0 < |x| < +Inf
+		allBits := int32(len(x.mant)) * _W
+		// build up numerator and denominator
+		z.a.neg = x.neg
+		switch {
+		case x.exp > allBits:
+			z.a.abs = z.a.abs.shl(x.mant, uint(x.exp-allBits))
+			z.b.abs = z.b.abs[:0] // == 1 (see Rat)
+			// z already in normal form
+		default:
+			z.a.abs = z.a.abs.set(x.mant)
+			z.b.abs = z.b.abs[:0] // == 1 (see Rat)
+			// z already in normal form
+		case x.exp < allBits:
+			z.a.abs = z.a.abs.set(x.mant)
+			t := z.b.abs.setUint64(1)
+			z.b.abs = t.shl(t, uint(allBits-x.exp))
+			z.norm()
+		}
+		return z, Exact
+
+	case zero:
+		return z.SetInt64(0), Exact
+
+	case inf:
+		return nil, makeAcc(x.neg)
+	}
+
+	panic("unreachable")
+}
+
+// Abs sets z to the (possibly rounded) value |x| (the absolute value of x)
+// and returns z.
+func (z *Float) Abs(x *Float) *Float {
+	z.Set(x)
+	z.neg = false
+	return z
+}
+
+// Neg sets z to the (possibly rounded) value of x with its sign negated,
+// and returns z.
+func (z *Float) Neg(x *Float) *Float {
+	z.Set(x)
+	z.neg = !z.neg
+	return z
+}
+
+func validateBinaryOperands(x, y *Float) {
+	if !debugFloat {
+		// avoid performance bugs
+		panic("validateBinaryOperands called but debugFloat is not set")
+	}
+	if len(x.mant) == 0 {
+		panic("empty mantissa for x")
+	}
+	if len(y.mant) == 0 {
+		panic("empty mantissa for y")
+	}
+}
+
+// z = x + y, ignoring signs of x and y for the addition
+// but using the sign of z for rounding the result.
+// x and y must have a non-empty mantissa and valid exponent.
+func (z *Float) uadd(x, y *Float) {
+	// Note: This implementation requires 2 shifts most of the
+	// time. It is also inefficient if exponents or precisions
+	// differ by wide margins. The following article describes
+	// an efficient (but much more complicated) implementation
+	// compatible with the internal representation used here:
+	//
+	// Vincent Lefèvre: "The Generic Multiple-Precision Floating-
+	// Point Addition With Exact Rounding (as in the MPFR Library)"
+	// http://www.vinc17.net/research/papers/rnc6.pdf
+
+	if debugFloat {
+		validateBinaryOperands(x, y)
+	}
+
+	// compute exponents ex, ey for mantissa with "binary point"
+	// on the right (mantissa.0) - use int64 to avoid overflow
+	ex := int64(x.exp) - int64(len(x.mant))*_W
+	ey := int64(y.exp) - int64(len(y.mant))*_W
+
+	al := alias(z.mant, x.mant) || alias(z.mant, y.mant)
+
+	// TODO(gri) having a combined add-and-shift primitive
+	//           could make this code significantly faster
+	switch {
+	case ex < ey:
+		if al {
+			t := nat(nil).shl(y.mant, uint(ey-ex))
+			z.mant = z.mant.add(x.mant, t)
+		} else {
+			z.mant = z.mant.shl(y.mant, uint(ey-ex))
+			z.mant = z.mant.add(x.mant, z.mant)
+		}
+	default:
+		// ex == ey, no shift needed
+		z.mant = z.mant.add(x.mant, y.mant)
+	case ex > ey:
+		if al {
+			t := nat(nil).shl(x.mant, uint(ex-ey))
+			z.mant = z.mant.add(t, y.mant)
+		} else {
+			z.mant = z.mant.shl(x.mant, uint(ex-ey))
+			z.mant = z.mant.add(z.mant, y.mant)
+		}
+		ex = ey
+	}
+	// len(z.mant) > 0
+
+	z.setExpAndRound(ex+int64(len(z.mant))*_W-fnorm(z.mant), 0)
+}
+
+// z = x - y for |x| > |y|, ignoring signs of x and y for the subtraction
+// but using the sign of z for rounding the result.
+// x and y must have a non-empty mantissa and valid exponent.
+func (z *Float) usub(x, y *Float) {
+	// This code is symmetric to uadd.
+	// We have not factored the common code out because
+	// eventually uadd (and usub) should be optimized
+	// by special-casing, and the code will diverge.
+
+	if debugFloat {
+		validateBinaryOperands(x, y)
+	}
+
+	ex := int64(x.exp) - int64(len(x.mant))*_W
+	ey := int64(y.exp) - int64(len(y.mant))*_W
+
+	al := alias(z.mant, x.mant) || alias(z.mant, y.mant)
+
+	switch {
+	case ex < ey:
+		if al {
+			t := nat(nil).shl(y.mant, uint(ey-ex))
+			z.mant = t.sub(x.mant, t)
+		} else {
+			z.mant = z.mant.shl(y.mant, uint(ey-ex))
+			z.mant = z.mant.sub(x.mant, z.mant)
+		}
+	default:
+		// ex == ey, no shift needed
+		z.mant = z.mant.sub(x.mant, y.mant)
+	case ex > ey:
+		if al {
+			t := nat(nil).shl(x.mant, uint(ex-ey))
+			z.mant = t.sub(t, y.mant)
+		} else {
+			z.mant = z.mant.shl(x.mant, uint(ex-ey))
+			z.mant = z.mant.sub(z.mant, y.mant)
+		}
+		ex = ey
+	}
+
+	// operands may have canceled each other out
+	if len(z.mant) == 0 {
+		z.acc = Exact
+		z.form = zero
+		z.neg = false
+		return
+	}
+	// len(z.mant) > 0
+
+	z.setExpAndRound(ex+int64(len(z.mant))*_W-fnorm(z.mant), 0)
+}
+
+// z = x * y, ignoring signs of x and y for the multiplication
+// but using the sign of z for rounding the result.
+// x and y must have a non-empty mantissa and valid exponent.
+func (z *Float) umul(x, y *Float) {
+	if debugFloat {
+		validateBinaryOperands(x, y)
+	}
+
+	// Note: This is doing too much work if the precision
+	// of z is less than the sum of the precisions of x
+	// and y which is often the case (e.g., if all floats
+	// have the same precision).
+	// TODO(gri) Optimize this for the common case.
+
+	e := int64(x.exp) + int64(y.exp)
+	if x == y {
+		z.mant = z.mant.sqr(x.mant)
+	} else {
+		z.mant = z.mant.mul(x.mant, y.mant)
+	}
+	z.setExpAndRound(e-fnorm(z.mant), 0)
+}
+
+// z = x / y, ignoring signs of x and y for the division
+// but using the sign of z for rounding the result.
+// x and y must have a non-empty mantissa and valid exponent.
+func (z *Float) uquo(x, y *Float) {
+	if debugFloat {
+		validateBinaryOperands(x, y)
+	}
+
+	// mantissa length in words for desired result precision + 1
+	// (at least one extra bit so we get the rounding bit after
+	// the division)
+	n := int(z.prec/_W) + 1
+
+	// compute adjusted x.mant such that we get enough result precision
+	xadj := x.mant
+	if d := n - len(x.mant) + len(y.mant); d > 0 {
+		// d extra words needed => add d "0 digits" to x
+		xadj = make(nat, len(x.mant)+d)
+		copy(xadj[d:], x.mant)
+	}
+	// TODO(gri): If we have too many digits (d < 0), we should be able
+	// to shorten x for faster division. But we must be extra careful
+	// with rounding in that case.
+
+	// Compute d before division since there may be aliasing of x.mant
+	// (via xadj) or y.mant with z.mant.
+	d := len(xadj) - len(y.mant)
+
+	// divide
+	var r nat
+	z.mant, r = z.mant.div(nil, xadj, y.mant)
+	e := int64(x.exp) - int64(y.exp) - int64(d-len(z.mant))*_W
+
+	// The result is long enough to include (at least) the rounding bit.
+	// If there's a non-zero remainder, the corresponding fractional part
+	// (if it were computed), would have a non-zero sticky bit (if it were
+	// zero, it couldn't have a non-zero remainder).
+	var sbit uint
+	if len(r) > 0 {
+		sbit = 1
+	}
+
+	z.setExpAndRound(e-fnorm(z.mant), sbit)
+}
+
+// ucmp returns -1, 0, or +1, depending on whether
+// |x| < |y|, |x| == |y|, or |x| > |y|.
+// x and y must have a non-empty mantissa and valid exponent.
+func (x *Float) ucmp(y *Float) int {
+	if debugFloat {
+		validateBinaryOperands(x, y)
+	}
+
+	switch {
+	case x.exp < y.exp:
+		return -1
+	case x.exp > y.exp:
+		return +1
+	}
+	// x.exp == y.exp
+
+	// compare mantissas
+	i := len(x.mant)
+	j := len(y.mant)
+	for i > 0 || j > 0 {
+		var xm, ym Word
+		if i > 0 {
+			i--
+			xm = x.mant[i]
+		}
+		if j > 0 {
+			j--
+			ym = y.mant[j]
+		}
+		switch {
+		case xm < ym:
+			return -1
+		case xm > ym:
+			return +1
+		}
+	}
+
+	return 0
+}
+
+// Handling of sign bit as defined by IEEE 754-2008, section 6.3:
+//
+// When neither the inputs nor result are NaN, the sign of a product or
+// quotient is the exclusive OR of the operands’ signs; the sign of a sum,
+// or of a difference x−y regarded as a sum x+(−y), differs from at most
+// one of the addends’ signs; and the sign of the result of conversions,
+// the quantize operation, the roundToIntegral operations, and the
+// roundToIntegralExact (see 5.3.1) is the sign of the first or only operand.
+// These rules shall apply even when operands or results are zero or infinite.
+//
+// When the sum of two operands with opposite signs (or the difference of
+// two operands with like signs) is exactly zero, the sign of that sum (or
+// difference) shall be +0 in all rounding-direction attributes except
+// roundTowardNegative; under that attribute, the sign of an exact zero
+// sum (or difference) shall be −0. However, x+x = x−(−x) retains the same
+// sign as x even when x is zero.
+//
+// See also: https://play.golang.org/p/RtH3UCt5IH
+
+// Add sets z to the rounded sum x+y and returns z. If z's precision is 0,
+// it is changed to the larger of x's or y's precision before the operation.
+// Rounding is performed according to z's precision and rounding mode; and
+// z's accuracy reports the result error relative to the exact (not rounded)
+// result. Add panics with ErrNaN if x and y are infinities with opposite
+// signs. The value of z is undefined in that case.
+func (z *Float) Add(x, y *Float) *Float {
+	if debugFloat {
+		x.validate()
+		y.validate()
+	}
+
+	if z.prec == 0 {
+		z.prec = umax32(x.prec, y.prec)
+	}
+
+	if x.form == finite && y.form == finite {
+		// x + y (common case)
+
+		// Below we set z.neg = x.neg, and when z aliases y this will
+		// change the y operand's sign. This is fine, because if an
+		// operand aliases the receiver it'll be overwritten, but we still
+		// want the original x.neg and y.neg values when we evaluate
+		// x.neg != y.neg, so we need to save y.neg before setting z.neg.
+		yneg := y.neg
+
+		z.neg = x.neg
+		if x.neg == yneg {
+			// x + y == x + y
+			// (-x) + (-y) == -(x + y)
+			z.uadd(x, y)
+		} else {
+			// x + (-y) == x - y == -(y - x)
+			// (-x) + y == y - x == -(x - y)
+			if x.ucmp(y) > 0 {
+				z.usub(x, y)
+			} else {
+				z.neg = !z.neg
+				z.usub(y, x)
+			}
+		}
+		if z.form == zero && z.mode == ToNegativeInf && z.acc == Exact {
+			z.neg = true
+		}
+		return z
+	}
+
+	if x.form == inf && y.form == inf && x.neg != y.neg {
+		// +Inf + -Inf
+		// -Inf + +Inf
+		// value of z is undefined but make sure it's valid
+		z.acc = Exact
+		z.form = zero
+		z.neg = false
+		panic(ErrNaN{"addition of infinities with opposite signs"})
+	}
+
+	if x.form == zero && y.form == zero {
+		// ±0 + ±0
+		z.acc = Exact
+		z.form = zero
+		z.neg = x.neg && y.neg // -0 + -0 == -0
+		return z
+	}
+
+	if x.form == inf || y.form == zero {
+		// ±Inf + y
+		// x + ±0
+		return z.Set(x)
+	}
+
+	// ±0 + y
+	// x + ±Inf
+	return z.Set(y)
+}
+
+// Sub sets z to the rounded difference x-y and returns z.
+// Precision, rounding, and accuracy reporting are as for Add.
+// Sub panics with ErrNaN if x and y are infinities with equal
+// signs. The value of z is undefined in that case.
+func (z *Float) Sub(x, y *Float) *Float {
+	if debugFloat {
+		x.validate()
+		y.validate()
+	}
+
+	if z.prec == 0 {
+		z.prec = umax32(x.prec, y.prec)
+	}
+
+	if x.form == finite && y.form == finite {
+		// x - y (common case)
+		yneg := y.neg
+		z.neg = x.neg
+		if x.neg != yneg {
+			// x - (-y) == x + y
+			// (-x) - y == -(x + y)
+			z.uadd(x, y)
+		} else {
+			// x - y == x - y == -(y - x)
+			// (-x) - (-y) == y - x == -(x - y)
+			if x.ucmp(y) > 0 {
+				z.usub(x, y)
+			} else {
+				z.neg = !z.neg
+				z.usub(y, x)
+			}
+		}
+		if z.form == zero && z.mode == ToNegativeInf && z.acc == Exact {
+			z.neg = true
+		}
+		return z
+	}
+
+	if x.form == inf && y.form == inf && x.neg == y.neg {
+		// +Inf - +Inf
+		// -Inf - -Inf
+		// value of z is undefined but make sure it's valid
+		z.acc = Exact
+		z.form = zero
+		z.neg = false
+		panic(ErrNaN{"subtraction of infinities with equal signs"})
+	}
+
+	if x.form == zero && y.form == zero {
+		// ±0 - ±0
+		z.acc = Exact
+		z.form = zero
+		z.neg = x.neg && !y.neg // -0 - +0 == -0
+		return z
+	}
+
+	if x.form == inf || y.form == zero {
+		// ±Inf - y
+		// x - ±0
+		return z.Set(x)
+	}
+
+	// ±0 - y
+	// x - ±Inf
+	return z.Neg(y)
+}
+
+// Mul sets z to the rounded product x*y and returns z.
+// Precision, rounding, and accuracy reporting are as for Add.
+// Mul panics with ErrNaN if one operand is zero and the other
+// operand an infinity. The value of z is undefined in that case.
+func (z *Float) Mul(x, y *Float) *Float {
+	if debugFloat {
+		x.validate()
+		y.validate()
+	}
+
+	if z.prec == 0 {
+		z.prec = umax32(x.prec, y.prec)
+	}
+
+	z.neg = x.neg != y.neg
+
+	if x.form == finite && y.form == finite {
+		// x * y (common case)
+		z.umul(x, y)
+		return z
+	}
+
+	z.acc = Exact
+	if x.form == zero && y.form == inf || x.form == inf && y.form == zero {
+		// ±0 * ±Inf
+		// ±Inf * ±0
+		// value of z is undefined but make sure it's valid
+		z.form = zero
+		z.neg = false
+		panic(ErrNaN{"multiplication of zero with infinity"})
+	}
+
+	if x.form == inf || y.form == inf {
+		// ±Inf * y
+		// x * ±Inf
+		z.form = inf
+		return z
+	}
+
+	// ±0 * y
+	// x * ±0
+	z.form = zero
+	return z
+}
+
+// Quo sets z to the rounded quotient x/y and returns z.
+// Precision, rounding, and accuracy reporting are as for Add.
+// Quo panics with ErrNaN if both operands are zero or infinities.
+// The value of z is undefined in that case.
+func (z *Float) Quo(x, y *Float) *Float {
+	if debugFloat {
+		x.validate()
+		y.validate()
+	}
+
+	if z.prec == 0 {
+		z.prec = umax32(x.prec, y.prec)
+	}
+
+	z.neg = x.neg != y.neg
+
+	if x.form == finite && y.form == finite {
+		// x / y (common case)
+		z.uquo(x, y)
+		return z
+	}
+
+	z.acc = Exact
+	if x.form == zero && y.form == zero || x.form == inf && y.form == inf {
+		// ±0 / ±0
+		// ±Inf / ±Inf
+		// value of z is undefined but make sure it's valid
+		z.form = zero
+		z.neg = false
+		panic(ErrNaN{"division of zero by zero or infinity by infinity"})
+	}
+
+	if x.form == zero || y.form == inf {
+		// ±0 / y
+		// x / ±Inf
+		z.form = zero
+		return z
+	}
+
+	// x / ±0
+	// ±Inf / y
+	z.form = inf
+	return z
+}
+
+// Cmp compares x and y and returns:
+//
+//   -1 if x <  y
+//    0 if x == y (incl. -0 == 0, -Inf == -Inf, and +Inf == +Inf)
+//   +1 if x >  y
+//
+func (x *Float) Cmp(y *Float) int {
+	if debugFloat {
+		x.validate()
+		y.validate()
+	}
+
+	mx := x.ord()
+	my := y.ord()
+	switch {
+	case mx < my:
+		return -1
+	case mx > my:
+		return +1
+	}
+	// mx == my
+
+	// only if |mx| == 1 we have to compare the mantissae
+	switch mx {
+	case -1:
+		return y.ucmp(x)
+	case +1:
+		return x.ucmp(y)
+	}
+
+	return 0
+}
+
+// ord classifies x and returns:
+//
+//	-2 if -Inf == x
+//	-1 if -Inf < x < 0
+//	 0 if x == 0 (signed or unsigned)
+//	+1 if 0 < x < +Inf
+//	+2 if x == +Inf
+//
+func (x *Float) ord() int {
+	var m int
+	switch x.form {
+	case finite:
+		m = 1
+	case zero:
+		return 0
+	case inf:
+		m = 2
+	}
+	if x.neg {
+		m = -m
+	}
+	return m
+}
+
+func umax32(x, y uint32) uint32 {
+	if x > y {
+		return x
+	}
+	return y
+}
diff --git a/contrib/go/_std_1.18/src/math/big/floatconv.go b/contrib/go/_std_1.18/src/math/big/floatconv.go
new file mode 100644
index 0000000000..57b7df3936
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/floatconv.go
@@ -0,0 +1,304 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements string-to-Float conversion functions.
+
+package big
+
+import (
+	"fmt"
+	"io"
+	"strings"
+)
+
+var floatZero Float
+
+// SetString sets z to the value of s and returns z and a boolean indicating
+// success. s must be a floating-point number of the same format as accepted
+// by Parse, with base argument 0. The entire string (not just a prefix) must
+// be valid for success. If the operation failed, the value of z is undefined
+// but the returned value is nil.
+func (z *Float) SetString(s string) (*Float, bool) {
+	if f, _, err := z.Parse(s, 0); err == nil {
+		return f, true
+	}
+	return nil, false
+}
+
+// scan is like Parse but reads the longest possible prefix representing a valid
+// floating point number from an io.ByteScanner rather than a string. It serves
+// as the implementation of Parse. It does not recognize ±Inf and does not expect
+// EOF at the end.
+func (z *Float) scan(r io.ByteScanner, base int) (f *Float, b int, err error) {
+	prec := z.prec
+	if prec == 0 {
+		prec = 64
+	}
+
+	// A reasonable value in case of an error.
+	z.form = zero
+
+	// sign
+	z.neg, err = scanSign(r)
+	if err != nil {
+		return
+	}
+
+	// mantissa
+	var fcount int // fractional digit count; valid if <= 0
+	z.mant, b, fcount, err = z.mant.scan(r, base, true)
+	if err != nil {
+		return
+	}
+
+	// exponent
+	var exp int64
+	var ebase int
+	exp, ebase, err = scanExponent(r, true, base == 0)
+	if err != nil {
+		return
+	}
+
+	// special-case 0
+	if len(z.mant) == 0 {
+		z.prec = prec
+		z.acc = Exact
+		z.form = zero
+		f = z
+		return
+	}
+	// len(z.mant) > 0
+
+	// The mantissa may have a radix point (fcount <= 0) and there
+	// may be a nonzero exponent exp. The radix point amounts to a
+	// division by b**(-fcount). An exponent means multiplication by
+	// ebase**exp. Finally, mantissa normalization (shift left) requires
+	// a correcting multiplication by 2**(-shiftcount). Multiplications
+	// are commutative, so we can apply them in any order as long as there
+	// is no loss of precision. We only have powers of 2 and 10, and
+	// we split powers of 10 into the product of the same powers of
+	// 2 and 5. This reduces the size of the multiplication factor
+	// needed for base-10 exponents.
+
+	// normalize mantissa and determine initial exponent contributions
+	exp2 := int64(len(z.mant))*_W - fnorm(z.mant)
+	exp5 := int64(0)
+
+	// determine binary or decimal exponent contribution of radix point
+	if fcount < 0 {
+		// The mantissa has a radix point ddd.dddd; and
+		// -fcount is the number of digits to the right
+		// of '.'. Adjust relevant exponent accordingly.
+		d := int64(fcount)
+		switch b {
+		case 10:
+			exp5 = d
+			fallthrough // 10**e == 5**e * 2**e
+		case 2:
+			exp2 += d
+		case 8:
+			exp2 += d * 3 // octal digits are 3 bits each
+		case 16:
+			exp2 += d * 4 // hexadecimal digits are 4 bits each
+		default:
+			panic("unexpected mantissa base")
+		}
+		// fcount consumed - not needed anymore
+	}
+
+	// take actual exponent into account
+	switch ebase {
+	case 10:
+		exp5 += exp
+		fallthrough // see fallthrough above
+	case 2:
+		exp2 += exp
+	default:
+		panic("unexpected exponent base")
+	}
+	// exp consumed - not needed anymore
+
+	// apply 2**exp2
+	if MinExp <= exp2 && exp2 <= MaxExp {
+		z.prec = prec
+		z.form = finite
+		z.exp = int32(exp2)
+		f = z
+	} else {
+		err = fmt.Errorf("exponent overflow")
+		return
+	}
+
+	if exp5 == 0 {
+		// no decimal exponent contribution
+		z.round(0)
+		return
+	}
+	// exp5 != 0
+
+	// apply 5**exp5
+	p := new(Float).SetPrec(z.Prec() + 64) // use more bits for p -- TODO(gri) what is the right number?
+	if exp5 < 0 {
+		z.Quo(z, p.pow5(uint64(-exp5)))
+	} else {
+		z.Mul(z, p.pow5(uint64(exp5)))
+	}
+
+	return
+}
+
+// These powers of 5 fit into a uint64.
+//
+//	for p, q := uint64(0), uint64(1); p < q; p, q = q, q*5 {
+//		fmt.Println(q)
+//	}
+//
+var pow5tab = [...]uint64{
+	1,
+	5,
+	25,
+	125,
+	625,
+	3125,
+	15625,
+	78125,
+	390625,
+	1953125,
+	9765625,
+	48828125,
+	244140625,
+	1220703125,
+	6103515625,
+	30517578125,
+	152587890625,
+	762939453125,
+	3814697265625,
+	19073486328125,
+	95367431640625,
+	476837158203125,
+	2384185791015625,
+	11920928955078125,
+	59604644775390625,
+	298023223876953125,
+	1490116119384765625,
+	7450580596923828125,
+}
+
+// pow5 sets z to 5**n and returns z.
+// n must not be negative.
+func (z *Float) pow5(n uint64) *Float {
+	const m = uint64(len(pow5tab) - 1)
+	if n <= m {
+		return z.SetUint64(pow5tab[n])
+	}
+	// n > m
+
+	z.SetUint64(pow5tab[m])
+	n -= m
+
+	// use more bits for f than for z
+	// TODO(gri) what is the right number?
+	f := new(Float).SetPrec(z.Prec() + 64).SetUint64(5)
+
+	for n > 0 {
+		if n&1 != 0 {
+			z.Mul(z, f)
+		}
+		f.Mul(f, f)
+		n >>= 1
+	}
+
+	return z
+}
+
+// Parse parses s which must contain a text representation of a floating-
+// point number with a mantissa in the given conversion base (the exponent
+// is always a decimal number), or a string representing an infinite value.
+//
+// For base 0, an underscore character ``_'' may appear between a base
+// prefix and an adjacent digit, and between successive digits; such
+// underscores do not change the value of the number, or the returned
+// digit count. Incorrect placement of underscores is reported as an
+// error if there are no other errors. If base != 0, underscores are
+// not recognized and thus terminate scanning like any other character
+// that is not a valid radix point or digit.
+//
+// It sets z to the (possibly rounded) value of the corresponding floating-
+// point value, and returns z, the actual base b, and an error err, if any.
+// The entire string (not just a prefix) must be consumed for success.
+// If z's precision is 0, it is changed to 64 before rounding takes effect.
+// The number must be of the form:
+//
+//     number    = [ sign ] ( float | "inf" | "Inf" ) .
+//     sign      = "+" | "-" .
+//     float     = ( mantissa | prefix pmantissa ) [ exponent ] .
+//     prefix    = "0" [ "b" | "B" | "o" | "O" | "x" | "X" ] .
+//     mantissa  = digits "." [ digits ] | digits | "." digits .
+//     pmantissa = [ "_" ] digits "." [ digits ] | [ "_" ] digits | "." digits .
+//     exponent  = ( "e" | "E" | "p" | "P" ) [ sign ] digits .
+//     digits    = digit { [ "_" ] digit } .
+//     digit     = "0" ... "9" | "a" ... "z" | "A" ... "Z" .
+//
+// The base argument must be 0, 2, 8, 10, or 16. Providing an invalid base
+// argument will lead to a run-time panic.
+//
+// For base 0, the number prefix determines the actual base: A prefix of
+// ``0b'' or ``0B'' selects base 2, ``0o'' or ``0O'' selects base 8, and
+// ``0x'' or ``0X'' selects base 16. Otherwise, the actual base is 10 and
+// no prefix is accepted. The octal prefix "0" is not supported (a leading
+// "0" is simply considered a "0").
+//
+// A "p" or "P" exponent indicates a base 2 (rather then base 10) exponent;
+// for instance, "0x1.fffffffffffffp1023" (using base 0) represents the
+// maximum float64 value. For hexadecimal mantissae, the exponent character
+// must be one of 'p' or 'P', if present (an "e" or "E" exponent indicator
+// cannot be distinguished from a mantissa digit).
+//
+// The returned *Float f is nil and the value of z is valid but not
+// defined if an error is reported.
+//
+func (z *Float) Parse(s string, base int) (f *Float, b int, err error) {
+	// scan doesn't handle ±Inf
+	if len(s) == 3 && (s == "Inf" || s == "inf") {
+		f = z.SetInf(false)
+		return
+	}
+	if len(s) == 4 && (s[0] == '+' || s[0] == '-') && (s[1:] == "Inf" || s[1:] == "inf") {
+		f = z.SetInf(s[0] == '-')
+		return
+	}
+
+	r := strings.NewReader(s)
+	if f, b, err = z.scan(r, base); err != nil {
+		return
+	}
+
+	// entire string must have been consumed
+	if ch, err2 := r.ReadByte(); err2 == nil {
+		err = fmt.Errorf("expected end of string, found %q", ch)
+	} else if err2 != io.EOF {
+		err = err2
+	}
+
+	return
+}
+
+// ParseFloat is like f.Parse(s, base) with f set to the given precision
+// and rounding mode.
+func ParseFloat(s string, base int, prec uint, mode RoundingMode) (f *Float, b int, err error) {
+	return new(Float).SetPrec(prec).SetMode(mode).Parse(s, base)
+}
+
+var _ fmt.Scanner = (*Float)(nil) // *Float must implement fmt.Scanner
+
+// Scan is a support routine for fmt.Scanner; it sets z to the value of
+// the scanned number. It accepts formats whose verbs are supported by
+// fmt.Scan for floating point values, which are:
+// 'b' (binary), 'e', 'E', 'f', 'F', 'g' and 'G'.
+// Scan doesn't handle ±Inf.
+func (z *Float) Scan(s fmt.ScanState, ch rune) error {
+	s.SkipSpace()
+	_, _, err := z.scan(byteReader{s}, 0)
+	return err
+}
diff --git a/contrib/go/_std_1.18/src/math/big/floatmarsh.go b/contrib/go/_std_1.18/src/math/big/floatmarsh.go
new file mode 100644
index 0000000000..d1c1dab069
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/floatmarsh.go
@@ -0,0 +1,120 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements encoding/decoding of Floats.
+
+package big
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+// Gob codec version. Permits backward-compatible changes to the encoding.
+const floatGobVersion byte = 1
+
+// GobEncode implements the gob.GobEncoder interface.
+// The Float value and all its attributes (precision,
+// rounding mode, accuracy) are marshaled.
+func (x *Float) GobEncode() ([]byte, error) {
+	if x == nil {
+		return nil, nil
+	}
+
+	// determine max. space (bytes) required for encoding
+	sz := 1 + 1 + 4 // version + mode|acc|form|neg (3+2+2+1bit) + prec
+	n := 0          // number of mantissa words
+	if x.form == finite {
+		// add space for mantissa and exponent
+		n = int((x.prec + (_W - 1)) / _W) // required mantissa length in words for given precision
+		// actual mantissa slice could be shorter (trailing 0's) or longer (unused bits):
+		// - if shorter, only encode the words present
+		// - if longer, cut off unused words when encoding in bytes
+		//   (in practice, this should never happen since rounding
+		//   takes care of it, but be safe and do it always)
+		if len(x.mant) < n {
+			n = len(x.mant)
+		}
+		// len(x.mant) >= n
+		sz += 4 + n*_S // exp + mant
+	}
+	buf := make([]byte, sz)
+
+	buf[0] = floatGobVersion
+	b := byte(x.mode&7)<<5 | byte((x.acc+1)&3)<<3 | byte(x.form&3)<<1
+	if x.neg {
+		b |= 1
+	}
+	buf[1] = b
+	binary.BigEndian.PutUint32(buf[2:], x.prec)
+
+	if x.form == finite {
+		binary.BigEndian.PutUint32(buf[6:], uint32(x.exp))
+		x.mant[len(x.mant)-n:].bytes(buf[10:]) // cut off unused trailing words
+	}
+
+	return buf, nil
+}
+
+// GobDecode implements the gob.GobDecoder interface.
+// The result is rounded per the precision and rounding mode of
+// z unless z's precision is 0, in which case z is set exactly
+// to the decoded value.
+func (z *Float) GobDecode(buf []byte) error {
+	if len(buf) == 0 {
+		// Other side sent a nil or default value.
+		*z = Float{}
+		return nil
+	}
+
+	if buf[0] != floatGobVersion {
+		return fmt.Errorf("Float.GobDecode: encoding version %d not supported", buf[0])
+	}
+
+	oldPrec := z.prec
+	oldMode := z.mode
+
+	b := buf[1]
+	z.mode = RoundingMode((b >> 5) & 7)
+	z.acc = Accuracy((b>>3)&3) - 1
+	z.form = form((b >> 1) & 3)
+	z.neg = b&1 != 0
+	z.prec = binary.BigEndian.Uint32(buf[2:])
+
+	if z.form == finite {
+		z.exp = int32(binary.BigEndian.Uint32(buf[6:]))
+		z.mant = z.mant.setBytes(buf[10:])
+	}
+
+	if oldPrec != 0 {
+		z.mode = oldMode
+		z.SetPrec(uint(oldPrec))
+	}
+
+	return nil
+}
+
+// MarshalText implements the encoding.TextMarshaler interface.
+// Only the Float value is marshaled (in full precision), other
+// attributes such as precision or accuracy are ignored.
+func (x *Float) MarshalText() (text []byte, err error) {
+	if x == nil {
+		return []byte("<nil>"), nil
+	}
+	var buf []byte
+	return x.Append(buf, 'g', -1), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface.
+// The result is rounded per the precision and rounding mode of z.
+// If z's precision is 0, it is changed to 64 before rounding takes
+// effect.
+func (z *Float) UnmarshalText(text []byte) error {
+	// TODO(gri): get rid of the []byte/string conversion
+	_, _, err := z.Parse(string(text), 0)
+	if err != nil {
+		err = fmt.Errorf("math/big: cannot unmarshal %q into a *big.Float (%v)", text, err)
+	}
+	return err
+}
diff --git a/contrib/go/_std_1.18/src/math/big/ftoa.go b/contrib/go/_std_1.18/src/math/big/ftoa.go
new file mode 100644
index 0000000000..5506e6e425
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/ftoa.go
@@ -0,0 +1,536 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements Float-to-string conversion functions.
+// It is closely following the corresponding implementation
+// in strconv/ftoa.go, but modified and simplified for Float.
+
+package big
+
+import (
+	"bytes"
+	"fmt"
+	"strconv"
+)
+
+// Text converts the floating-point number x to a string according
+// to the given format and precision prec. The format is one of:
+//
+//	'e'	-d.dddde±dd, decimal exponent, at least two (possibly 0) exponent digits
+//	'E'	-d.ddddE±dd, decimal exponent, at least two (possibly 0) exponent digits
+//	'f'	-ddddd.dddd, no exponent
+//	'g'	like 'e' for large exponents, like 'f' otherwise
+//	'G'	like 'E' for large exponents, like 'f' otherwise
+//	'x'	-0xd.dddddp±dd, hexadecimal mantissa, decimal power of two exponent
+//	'p'	-0x.dddp±dd, hexadecimal mantissa, decimal power of two exponent (non-standard)
+//	'b'	-ddddddp±dd, decimal mantissa, decimal power of two exponent (non-standard)
+//
+// For the power-of-two exponent formats, the mantissa is printed in normalized form:
+//
+//	'x'	hexadecimal mantissa in [1, 2), or 0
+//	'p'	hexadecimal mantissa in [½, 1), or 0
+//	'b'	decimal integer mantissa using x.Prec() bits, or 0
+//
+// Note that the 'x' form is the one used by most other languages and libraries.
+//
+// If format is a different character, Text returns a "%" followed by the
+// unrecognized format character.
+//
+// The precision prec controls the number of digits (excluding the exponent)
+// printed by the 'e', 'E', 'f', 'g', 'G', and 'x' formats.
+// For 'e', 'E', 'f', and 'x', it is the number of digits after the decimal point.
+// For 'g' and 'G' it is the total number of digits. A negative precision selects
+// the smallest number of decimal digits necessary to identify the value x uniquely
+// using x.Prec() mantissa bits.
+// The prec value is ignored for the 'b' and 'p' formats.
+func (x *Float) Text(format byte, prec int) string {
+	cap := 10 // TODO(gri) determine a good/better value here
+	if prec > 0 {
+		cap += prec
+	}
+	return string(x.Append(make([]byte, 0, cap), format, prec))
+}
+
+// String formats x like x.Text('g', 10).
+// (String must be called explicitly, Float.Format does not support %s verb.)
+func (x *Float) String() string {
+	return x.Text('g', 10)
+}
+
+// Append appends to buf the string form of the floating-point number x,
+// as generated by x.Text, and returns the extended buffer.
+func (x *Float) Append(buf []byte, fmt byte, prec int) []byte {
+	// sign
+	if x.neg {
+		buf = append(buf, '-')
+	}
+
+	// Inf
+	if x.form == inf {
+		if !x.neg {
+			buf = append(buf, '+')
+		}
+		return append(buf, "Inf"...)
+	}
+
+	// pick off easy formats
+	switch fmt {
+	case 'b':
+		return x.fmtB(buf)
+	case 'p':
+		return x.fmtP(buf)
+	case 'x':
+		return x.fmtX(buf, prec)
+	}
+
+	// Algorithm:
+	//   1) convert Float to multiprecision decimal
+	//   2) round to desired precision
+	//   3) read digits out and format
+
+	// 1) convert Float to multiprecision decimal
+	var d decimal // == 0.0
+	if x.form == finite {
+		// x != 0
+		d.init(x.mant, int(x.exp)-x.mant.bitLen())
+	}
+
+	// 2) round to desired precision
+	shortest := false
+	if prec < 0 {
+		shortest = true
+		roundShortest(&d, x)
+		// Precision for shortest representation mode.
+		switch fmt {
+		case 'e', 'E':
+			prec = len(d.mant) - 1
+		case 'f':
+			prec = max(len(d.mant)-d.exp, 0)
+		case 'g', 'G':
+			prec = len(d.mant)
+		}
+	} else {
+		// round appropriately
+		switch fmt {
+		case 'e', 'E':
+			// one digit before and number of digits after decimal point
+			d.round(1 + prec)
+		case 'f':
+			// number of digits before and after decimal point
+			d.round(d.exp + prec)
+		case 'g', 'G':
+			if prec == 0 {
+				prec = 1
+			}
+			d.round(prec)
+		}
+	}
+
+	// 3) read digits out and format
+	switch fmt {
+	case 'e', 'E':
+		return fmtE(buf, fmt, prec, d)
+	case 'f':
+		return fmtF(buf, prec, d)
+	case 'g', 'G':
+		// trim trailing fractional zeros in %e format
+		eprec := prec
+		if eprec > len(d.mant) && len(d.mant) >= d.exp {
+			eprec = len(d.mant)
+		}
+		// %e is used if the exponent from the conversion
+		// is less than -4 or greater than or equal to the precision.
+		// If precision was the shortest possible, use eprec = 6 for
+		// this decision.
+		if shortest {
+			eprec = 6
+		}
+		exp := d.exp - 1
+		if exp < -4 || exp >= eprec {
+			if prec > len(d.mant) {
+				prec = len(d.mant)
+			}
+			return fmtE(buf, fmt+'e'-'g', prec-1, d)
+		}
+		if prec > d.exp {
+			prec = len(d.mant)
+		}
+		return fmtF(buf, max(prec-d.exp, 0), d)
+	}
+
+	// unknown format
+	if x.neg {
+		buf = buf[:len(buf)-1] // sign was added prematurely - remove it again
+	}
+	return append(buf, '%', fmt)
+}
+
+func roundShortest(d *decimal, x *Float) {
+	// if the mantissa is zero, the number is zero - stop now
+	if len(d.mant) == 0 {
+		return
+	}
+
+	// Approach: All numbers in the interval [x - 1/2ulp, x + 1/2ulp]
+	// (possibly exclusive) round to x for the given precision of x.
+	// Compute the lower and upper bound in decimal form and find the
+	// shortest decimal number d such that lower <= d <= upper.
+
+	// TODO(gri) strconv/ftoa.do describes a shortcut in some cases.
+	// See if we can use it (in adjusted form) here as well.
+
+	// 1) Compute normalized mantissa mant and exponent exp for x such
+	// that the lsb of mant corresponds to 1/2 ulp for the precision of
+	// x (i.e., for mant we want x.prec + 1 bits).
+	mant := nat(nil).set(x.mant)
+	exp := int(x.exp) - mant.bitLen()
+	s := mant.bitLen() - int(x.prec+1)
+	switch {
+	case s < 0:
+		mant = mant.shl(mant, uint(-s))
+	case s > 0:
+		mant = mant.shr(mant, uint(+s))
+	}
+	exp += s
+	// x = mant * 2**exp with lsb(mant) == 1/2 ulp of x.prec
+
+	// 2) Compute lower bound by subtracting 1/2 ulp.
+	var lower decimal
+	var tmp nat
+	lower.init(tmp.sub(mant, natOne), exp)
+
+	// 3) Compute upper bound by adding 1/2 ulp.
+	var upper decimal
+	upper.init(tmp.add(mant, natOne), exp)
+
+	// The upper and lower bounds are possible outputs only if
+	// the original mantissa is even, so that ToNearestEven rounding
+	// would round to the original mantissa and not the neighbors.
+	inclusive := mant[0]&2 == 0 // test bit 1 since original mantissa was shifted by 1
+
+	// Now we can figure out the minimum number of digits required.
+	// Walk along until d has distinguished itself from upper and lower.
+	for i, m := range d.mant {
+		l := lower.at(i)
+		u := upper.at(i)
+
+		// Okay to round down (truncate) if lower has a different digit
+		// or if lower is inclusive and is exactly the result of rounding
+		// down (i.e., and we have reached the final digit of lower).
+		okdown := l != m || inclusive && i+1 == len(lower.mant)
+
+		// Okay to round up if upper has a different digit and either upper
+		// is inclusive or upper is bigger than the result of rounding up.
+		okup := m != u && (inclusive || m+1 < u || i+1 < len(upper.mant))
+
+		// If it's okay to do either, then round to the nearest one.
+		// If it's okay to do only one, do it.
+		switch {
+		case okdown && okup:
+			d.round(i + 1)
+			return
+		case okdown:
+			d.roundDown(i + 1)
+			return
+		case okup:
+			d.roundUp(i + 1)
+			return
+		}
+	}
+}
+
+// %e: d.ddddde±dd
+func fmtE(buf []byte, fmt byte, prec int, d decimal) []byte {
+	// first digit
+	ch := byte('0')
+	if len(d.mant) > 0 {
+		ch = d.mant[0]
+	}
+	buf = append(buf, ch)
+
+	// .moredigits
+	if prec > 0 {
+		buf = append(buf, '.')
+		i := 1
+		m := min(len(d.mant), prec+1)
+		if i < m {
+			buf = append(buf, d.mant[i:m]...)
+			i = m
+		}
+		for ; i <= prec; i++ {
+			buf = append(buf, '0')
+		}
+	}
+
+	// e±
+	buf = append(buf, fmt)
+	var exp int64
+	if len(d.mant) > 0 {
+		exp = int64(d.exp) - 1 // -1 because first digit was printed before '.'
+	}
+	if exp < 0 {
+		ch = '-'
+		exp = -exp
+	} else {
+		ch = '+'
+	}
+	buf = append(buf, ch)
+
+	// dd...d
+	if exp < 10 {
+		buf = append(buf, '0') // at least 2 exponent digits
+	}
+	return strconv.AppendInt(buf, exp, 10)
+}
+
+// %f: ddddddd.ddddd
+func fmtF(buf []byte, prec int, d decimal) []byte {
+	// integer, padded with zeros as needed
+	if d.exp > 0 {
+		m := min(len(d.mant), d.exp)
+		buf = append(buf, d.mant[:m]...)
+		for ; m < d.exp; m++ {
+			buf = append(buf, '0')
+		}
+	} else {
+		buf = append(buf, '0')
+	}
+
+	// fraction
+	if prec > 0 {
+		buf = append(buf, '.')
+		for i := 0; i < prec; i++ {
+			buf = append(buf, d.at(d.exp+i))
+		}
+	}
+
+	return buf
+}
+
+// fmtB appends the string of x in the format mantissa "p" exponent
+// with a decimal mantissa and a binary exponent, or 0" if x is zero,
+// and returns the extended buffer.
+// The mantissa is normalized such that is uses x.Prec() bits in binary
+// representation.
+// The sign of x is ignored, and x must not be an Inf.
+// (The caller handles Inf before invoking fmtB.)
+func (x *Float) fmtB(buf []byte) []byte {
+	if x.form == zero {
+		return append(buf, '0')
+	}
+
+	if debugFloat && x.form != finite {
+		panic("non-finite float")
+	}
+	// x != 0
+
+	// adjust mantissa to use exactly x.prec bits
+	m := x.mant
+	switch w := uint32(len(x.mant)) * _W; {
+	case w < x.prec:
+		m = nat(nil).shl(m, uint(x.prec-w))
+	case w > x.prec:
+		m = nat(nil).shr(m, uint(w-x.prec))
+	}
+
+	buf = append(buf, m.utoa(10)...)
+	buf = append(buf, 'p')
+	e := int64(x.exp) - int64(x.prec)
+	if e >= 0 {
+		buf = append(buf, '+')
+	}
+	return strconv.AppendInt(buf, e, 10)
+}
+
+// fmtX appends the string of x in the format "0x1." mantissa "p" exponent
+// with a hexadecimal mantissa and a binary exponent, or "0x0p0" if x is zero,
+// and returns the extended buffer.
+// A non-zero mantissa is normalized such that 1.0 <= mantissa < 2.0.
+// The sign of x is ignored, and x must not be an Inf.
+// (The caller handles Inf before invoking fmtX.)
+func (x *Float) fmtX(buf []byte, prec int) []byte {
+	if x.form == zero {
+		buf = append(buf, "0x0"...)
+		if prec > 0 {
+			buf = append(buf, '.')
+			for i := 0; i < prec; i++ {
+				buf = append(buf, '0')
+			}
+		}
+		buf = append(buf, "p+00"...)
+		return buf
+	}
+
+	if debugFloat && x.form != finite {
+		panic("non-finite float")
+	}
+
+	// round mantissa to n bits
+	var n uint
+	if prec < 0 {
+		n = 1 + (x.MinPrec()-1+3)/4*4 // round MinPrec up to 1 mod 4
+	} else {
+		n = 1 + 4*uint(prec)
+	}
+	// n%4 == 1
+	x = new(Float).SetPrec(n).SetMode(x.mode).Set(x)
+
+	// adjust mantissa to use exactly n bits
+	m := x.mant
+	switch w := uint(len(x.mant)) * _W; {
+	case w < n:
+		m = nat(nil).shl(m, n-w)
+	case w > n:
+		m = nat(nil).shr(m, w-n)
+	}
+	exp64 := int64(x.exp) - 1 // avoid wrap-around
+
+	hm := m.utoa(16)
+	if debugFloat && hm[0] != '1' {
+		panic("incorrect mantissa: " + string(hm))
+	}
+	buf = append(buf, "0x1"...)
+	if len(hm) > 1 {
+		buf = append(buf, '.')
+		buf = append(buf, hm[1:]...)
+	}
+
+	buf = append(buf, 'p')
+	if exp64 >= 0 {
+		buf = append(buf, '+')
+	} else {
+		exp64 = -exp64
+		buf = append(buf, '-')
+	}
+	// Force at least two exponent digits, to match fmt.
+	if exp64 < 10 {
+		buf = append(buf, '0')
+	}
+	return strconv.AppendInt(buf, exp64, 10)
+}
+
+// fmtP appends the string of x in the format "0x." mantissa "p" exponent
+// with a hexadecimal mantissa and a binary exponent, or "0" if x is zero,
+// and returns the extended buffer.
+// The mantissa is normalized such that 0.5 <= 0.mantissa < 1.0.
+// The sign of x is ignored, and x must not be an Inf.
+// (The caller handles Inf before invoking fmtP.)
+func (x *Float) fmtP(buf []byte) []byte {
+	if x.form == zero {
+		return append(buf, '0')
+	}
+
+	if debugFloat && x.form != finite {
+		panic("non-finite float")
+	}
+	// x != 0
+
+	// remove trailing 0 words early
+	// (no need to convert to hex 0's and trim later)
+	m := x.mant
+	i := 0
+	for i < len(m) && m[i] == 0 {
+		i++
+	}
+	m = m[i:]
+
+	buf = append(buf, "0x."...)
+	buf = append(buf, bytes.TrimRight(m.utoa(16), "0")...)
+	buf = append(buf, 'p')
+	if x.exp >= 0 {
+		buf = append(buf, '+')
+	}
+	return strconv.AppendInt(buf, int64(x.exp), 10)
+}
+
+func min(x, y int) int {
+	if x < y {
+		return x
+	}
+	return y
+}
+
+var _ fmt.Formatter = &floatZero // *Float must implement fmt.Formatter
+
+// Format implements fmt.Formatter. It accepts all the regular
+// formats for floating-point numbers ('b', 'e', 'E', 'f', 'F',
+// 'g', 'G', 'x') as well as 'p' and 'v'. See (*Float).Text for the
+// interpretation of 'p'. The 'v' format is handled like 'g'.
+// Format also supports specification of the minimum precision
+// in digits, the output field width, as well as the format flags
+// '+' and ' ' for sign control, '0' for space or zero padding,
+// and '-' for left or right justification. See the fmt package
+// for details.
+func (x *Float) Format(s fmt.State, format rune) {
+	prec, hasPrec := s.Precision()
+	if !hasPrec {
+		prec = 6 // default precision for 'e', 'f'
+	}
+
+	switch format {
+	case 'e', 'E', 'f', 'b', 'p', 'x':
+		// nothing to do
+	case 'F':
+		// (*Float).Text doesn't support 'F'; handle like 'f'
+		format = 'f'
+	case 'v':
+		// handle like 'g'
+		format = 'g'
+		fallthrough
+	case 'g', 'G':
+		if !hasPrec {
+			prec = -1 // default precision for 'g', 'G'
+		}
+	default:
+		fmt.Fprintf(s, "%%!%c(*big.Float=%s)", format, x.String())
+		return
+	}
+	var buf []byte
+	buf = x.Append(buf, byte(format), prec)
+	if len(buf) == 0 {
+		buf = []byte("?") // should never happen, but don't crash
+	}
+	// len(buf) > 0
+
+	var sign string
+	switch {
+	case buf[0] == '-':
+		sign = "-"
+		buf = buf[1:]
+	case buf[0] == '+':
+		// +Inf
+		sign = "+"
+		if s.Flag(' ') {
+			sign = " "
+		}
+		buf = buf[1:]
+	case s.Flag('+'):
+		sign = "+"
+	case s.Flag(' '):
+		sign = " "
+	}
+
+	var padding int
+	if width, hasWidth := s.Width(); hasWidth && width > len(sign)+len(buf) {
+		padding = width - len(sign) - len(buf)
+	}
+
+	switch {
+	case s.Flag('0') && !x.IsInf():
+		// 0-padding on left
+		writeMultiple(s, sign, 1)
+		writeMultiple(s, "0", padding)
+		s.Write(buf)
+	case s.Flag('-'):
+		// padding on right
+		writeMultiple(s, sign, 1)
+		s.Write(buf)
+		writeMultiple(s, " ", padding)
+	default:
+		// padding on left
+		writeMultiple(s, " ", padding)
+		writeMultiple(s, sign, 1)
+		s.Write(buf)
+	}
+}
diff --git a/contrib/go/_std_1.18/src/math/big/int.go b/contrib/go/_std_1.18/src/math/big/int.go
new file mode 100644
index 0000000000..7647346486
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/int.go
@@ -0,0 +1,1218 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements signed multi-precision integers.
+
+package big
+
+import (
+	"fmt"
+	"io"
+	"math/rand"
+	"strings"
+)
+
+// An Int represents a signed multi-precision integer.
+// The zero value for an Int represents the value 0.
+//
+// Operations always take pointer arguments (*Int) rather
+// than Int values, and each unique Int value requires
+// its own unique *Int pointer. To "copy" an Int value,
+// an existing (or newly allocated) Int must be set to
+// a new value using the Int.Set method; shallow copies
+// of Ints are not supported and may lead to errors.
+type Int struct {
+	neg bool // sign
+	abs nat  // absolute value of the integer
+}
+
+var intOne = &Int{false, natOne}
+
+// Sign returns:
+//
+//	-1 if x <  0
+//	 0 if x == 0
+//	+1 if x >  0
+//
+func (x *Int) Sign() int {
+	if len(x.abs) == 0 {
+		return 0
+	}
+	if x.neg {
+		return -1
+	}
+	return 1
+}
+
+// SetInt64 sets z to x and returns z.
+func (z *Int) SetInt64(x int64) *Int {
+	neg := false
+	if x < 0 {
+		neg = true
+		x = -x
+	}
+	z.abs = z.abs.setUint64(uint64(x))
+	z.neg = neg
+	return z
+}
+
+// SetUint64 sets z to x and returns z.
+func (z *Int) SetUint64(x uint64) *Int {
+	z.abs = z.abs.setUint64(x)
+	z.neg = false
+	return z
+}
+
+// NewInt allocates and returns a new Int set to x.
+func NewInt(x int64) *Int {
+	return new(Int).SetInt64(x)
+}
+
+// Set sets z to x and returns z.
+func (z *Int) Set(x *Int) *Int {
+	if z != x {
+		z.abs = z.abs.set(x.abs)
+		z.neg = x.neg
+	}
+	return z
+}
+
+// Bits provides raw (unchecked but fast) access to x by returning its
+// absolute value as a little-endian Word slice. The result and x share
+// the same underlying array.
+// Bits is intended to support implementation of missing low-level Int
+// functionality outside this package; it should be avoided otherwise.
+func (x *Int) Bits() []Word {
+	return x.abs
+}
+
+// SetBits provides raw (unchecked but fast) access to z by setting its
+// value to abs, interpreted as a little-endian Word slice, and returning
+// z. The result and abs share the same underlying array.
+// SetBits is intended to support implementation of missing low-level Int
+// functionality outside this package; it should be avoided otherwise.
+func (z *Int) SetBits(abs []Word) *Int {
+	z.abs = nat(abs).norm()
+	z.neg = false
+	return z
+}
+
+// Abs sets z to |x| (the absolute value of x) and returns z.
+func (z *Int) Abs(x *Int) *Int {
+	z.Set(x)
+	z.neg = false
+	return z
+}
+
+// Neg sets z to -x and returns z.
+func (z *Int) Neg(x *Int) *Int {
+	z.Set(x)
+	z.neg = len(z.abs) > 0 && !z.neg // 0 has no sign
+	return z
+}
+
+// Add sets z to the sum x+y and returns z.
+func (z *Int) Add(x, y *Int) *Int {
+	neg := x.neg
+	if x.neg == y.neg {
+		// x + y == x + y
+		// (-x) + (-y) == -(x + y)
+		z.abs = z.abs.add(x.abs, y.abs)
+	} else {
+		// x + (-y) == x - y == -(y - x)
+		// (-x) + y == y - x == -(x - y)
+		if x.abs.cmp(y.abs) >= 0 {
+			z.abs = z.abs.sub(x.abs, y.abs)
+		} else {
+			neg = !neg
+			z.abs = z.abs.sub(y.abs, x.abs)
+		}
+	}
+	z.neg = len(z.abs) > 0 && neg // 0 has no sign
+	return z
+}
+
+// Sub sets z to the difference x-y and returns z.
+func (z *Int) Sub(x, y *Int) *Int {
+	neg := x.neg
+	if x.neg != y.neg {
+		// x - (-y) == x + y
+		// (-x) - y == -(x + y)
+		z.abs = z.abs.add(x.abs, y.abs)
+	} else {
+		// x - y == x - y == -(y - x)
+		// (-x) - (-y) == y - x == -(x - y)
+		if x.abs.cmp(y.abs) >= 0 {
+			z.abs = z.abs.sub(x.abs, y.abs)
+		} else {
+			neg = !neg
+			z.abs = z.abs.sub(y.abs, x.abs)
+		}
+	}
+	z.neg = len(z.abs) > 0 && neg // 0 has no sign
+	return z
+}
+
+// Mul sets z to the product x*y and returns z.
+func (z *Int) Mul(x, y *Int) *Int {
+	// x * y == x * y
+	// x * (-y) == -(x * y)
+	// (-x) * y == -(x * y)
+	// (-x) * (-y) == x * y
+	if x == y {
+		z.abs = z.abs.sqr(x.abs)
+		z.neg = false
+		return z
+	}
+	z.abs = z.abs.mul(x.abs, y.abs)
+	z.neg = len(z.abs) > 0 && x.neg != y.neg // 0 has no sign
+	return z
+}
+
+// MulRange sets z to the product of all integers
+// in the range [a, b] inclusively and returns z.
+// If a > b (empty range), the result is 1.
+func (z *Int) MulRange(a, b int64) *Int {
+	switch {
+	case a > b:
+		return z.SetInt64(1) // empty range
+	case a <= 0 && b >= 0:
+		return z.SetInt64(0) // range includes 0
+	}
+	// a <= b && (b < 0 || a > 0)
+
+	neg := false
+	if a < 0 {
+		neg = (b-a)&1 == 0
+		a, b = -b, -a
+	}
+
+	z.abs = z.abs.mulRange(uint64(a), uint64(b))
+	z.neg = neg
+	return z
+}
+
+// Binomial sets z to the binomial coefficient of (n, k) and returns z.
+func (z *Int) Binomial(n, k int64) *Int {
+	// reduce the number of multiplications by reducing k
+	if n/2 < k && k <= n {
+		k = n - k // Binomial(n, k) == Binomial(n, n-k)
+	}
+	var a, b Int
+	a.MulRange(n-k+1, n)
+	b.MulRange(1, k)
+	return z.Quo(&a, &b)
+}
+
+// Quo sets z to the quotient x/y for y != 0 and returns z.
+// If y == 0, a division-by-zero run-time panic occurs.
+// Quo implements truncated division (like Go); see QuoRem for more details.
+func (z *Int) Quo(x, y *Int) *Int {
+	z.abs, _ = z.abs.div(nil, x.abs, y.abs)
+	z.neg = len(z.abs) > 0 && x.neg != y.neg // 0 has no sign
+	return z
+}
+
+// Rem sets z to the remainder x%y for y != 0 and returns z.
+// If y == 0, a division-by-zero run-time panic occurs.
+// Rem implements truncated modulus (like Go); see QuoRem for more details.
+func (z *Int) Rem(x, y *Int) *Int {
+	_, z.abs = nat(nil).div(z.abs, x.abs, y.abs)
+	z.neg = len(z.abs) > 0 && x.neg // 0 has no sign
+	return z
+}
+
+// QuoRem sets z to the quotient x/y and r to the remainder x%y
+// and returns the pair (z, r) for y != 0.
+// If y == 0, a division-by-zero run-time panic occurs.
+//
+// QuoRem implements T-division and modulus (like Go):
+//
+//	q = x/y      with the result truncated to zero
+//	r = x - y*q
+//
+// (See Daan Leijen, ``Division and Modulus for Computer Scientists''.)
+// See DivMod for Euclidean division and modulus (unlike Go).
+//
+func (z *Int) QuoRem(x, y, r *Int) (*Int, *Int) {
+	z.abs, r.abs = z.abs.div(r.abs, x.abs, y.abs)
+	z.neg, r.neg = len(z.abs) > 0 && x.neg != y.neg, len(r.abs) > 0 && x.neg // 0 has no sign
+	return z, r
+}
+
+// Div sets z to the quotient x/y for y != 0 and returns z.
+// If y == 0, a division-by-zero run-time panic occurs.
+// Div implements Euclidean division (unlike Go); see DivMod for more details.
+func (z *Int) Div(x, y *Int) *Int {
+	y_neg := y.neg // z may be an alias for y
+	var r Int
+	z.QuoRem(x, y, &r)
+	if r.neg {
+		if y_neg {
+			z.Add(z, intOne)
+		} else {
+			z.Sub(z, intOne)
+		}
+	}
+	return z
+}
+
+// Mod sets z to the modulus x%y for y != 0 and returns z.
+// If y == 0, a division-by-zero run-time panic occurs.
+// Mod implements Euclidean modulus (unlike Go); see DivMod for more details.
+func (z *Int) Mod(x, y *Int) *Int {
+	y0 := y // save y
+	if z == y || alias(z.abs, y.abs) {
+		y0 = new(Int).Set(y)
+	}
+	var q Int
+	q.QuoRem(x, y, z)
+	if z.neg {
+		if y0.neg {
+			z.Sub(z, y0)
+		} else {
+			z.Add(z, y0)
+		}
+	}
+	return z
+}
+
+// DivMod sets z to the quotient x div y and m to the modulus x mod y
+// and returns the pair (z, m) for y != 0.
+// If y == 0, a division-by-zero run-time panic occurs.
+//
+// DivMod implements Euclidean division and modulus (unlike Go):
+//
+//	q = x div y  such that
+//	m = x - y*q  with 0 <= m < |y|
+//
+// (See Raymond T. Boute, ``The Euclidean definition of the functions
+// div and mod''. ACM Transactions on Programming Languages and
+// Systems (TOPLAS), 14(2):127-144, New York, NY, USA, 4/1992.
+// ACM press.)
+// See QuoRem for T-division and modulus (like Go).
+//
+func (z *Int) DivMod(x, y, m *Int) (*Int, *Int) {
+	y0 := y // save y
+	if z == y || alias(z.abs, y.abs) {
+		y0 = new(Int).Set(y)
+	}
+	z.QuoRem(x, y, m)
+	if m.neg {
+		if y0.neg {
+			z.Add(z, intOne)
+			m.Sub(m, y0)
+		} else {
+			z.Sub(z, intOne)
+			m.Add(m, y0)
+		}
+	}
+	return z, m
+}
+
+// Cmp compares x and y and returns:
+//
+//   -1 if x <  y
+//    0 if x == y
+//   +1 if x >  y
+//
+func (x *Int) Cmp(y *Int) (r int) {
+	// x cmp y == x cmp y
+	// x cmp (-y) == x
+	// (-x) cmp y == y
+	// (-x) cmp (-y) == -(x cmp y)
+	switch {
+	case x == y:
+		// nothing to do
+	case x.neg == y.neg:
+		r = x.abs.cmp(y.abs)
+		if x.neg {
+			r = -r
+		}
+	case x.neg:
+		r = -1
+	default:
+		r = 1
+	}
+	return
+}
+
+// CmpAbs compares the absolute values of x and y and returns:
+//
+//   -1 if |x| <  |y|
+//    0 if |x| == |y|
+//   +1 if |x| >  |y|
+//
+func (x *Int) CmpAbs(y *Int) int {
+	return x.abs.cmp(y.abs)
+}
+
+// low32 returns the least significant 32 bits of x.
+func low32(x nat) uint32 {
+	if len(x) == 0 {
+		return 0
+	}
+	return uint32(x[0])
+}
+
+// low64 returns the least significant 64 bits of x.
+func low64(x nat) uint64 {
+	if len(x) == 0 {
+		return 0
+	}
+	v := uint64(x[0])
+	if _W == 32 && len(x) > 1 {
+		return uint64(x[1])<<32 | v
+	}
+	return v
+}
+
+// Int64 returns the int64 representation of x.
+// If x cannot be represented in an int64, the result is undefined.
+func (x *Int) Int64() int64 {
+	v := int64(low64(x.abs))
+	if x.neg {
+		v = -v
+	}
+	return v
+}
+
+// Uint64 returns the uint64 representation of x.
+// If x cannot be represented in a uint64, the result is undefined.
+func (x *Int) Uint64() uint64 {
+	return low64(x.abs)
+}
+
+// IsInt64 reports whether x can be represented as an int64.
+func (x *Int) IsInt64() bool {
+	if len(x.abs) <= 64/_W {
+		w := int64(low64(x.abs))
+		return w >= 0 || x.neg && w == -w
+	}
+	return false
+}
+
+// IsUint64 reports whether x can be represented as a uint64.
+func (x *Int) IsUint64() bool {
+	return !x.neg && len(x.abs) <= 64/_W
+}
+
+// SetString sets z to the value of s, interpreted in the given base,
+// and returns z and a boolean indicating success. The entire string
+// (not just a prefix) must be valid for success. If SetString fails,
+// the value of z is undefined but the returned value is nil.
+//
+// The base argument must be 0 or a value between 2 and MaxBase.
+// For base 0, the number prefix determines the actual base: A prefix of
+// ``0b'' or ``0B'' selects base 2, ``0'', ``0o'' or ``0O'' selects base 8,
+// and ``0x'' or ``0X'' selects base 16. Otherwise, the selected base is 10
+// and no prefix is accepted.
+//
+// For bases <= 36, lower and upper case letters are considered the same:
+// The letters 'a' to 'z' and 'A' to 'Z' represent digit values 10 to 35.
+// For bases > 36, the upper case letters 'A' to 'Z' represent the digit
+// values 36 to 61.
+//
+// For base 0, an underscore character ``_'' may appear between a base
+// prefix and an adjacent digit, and between successive digits; such
+// underscores do not change the value of the number.
+// Incorrect placement of underscores is reported as an error if there
+// are no other errors. If base != 0, underscores are not recognized
+// and act like any other character that is not a valid digit.
+//
+func (z *Int) SetString(s string, base int) (*Int, bool) {
+	return z.setFromScanner(strings.NewReader(s), base)
+}
+
+// setFromScanner implements SetString given an io.ByteScanner.
+// For documentation see comments of SetString.
+func (z *Int) setFromScanner(r io.ByteScanner, base int) (*Int, bool) {
+	if _, _, err := z.scan(r, base); err != nil {
+		return nil, false
+	}
+	// entire content must have been consumed
+	if _, err := r.ReadByte(); err != io.EOF {
+		return nil, false
+	}
+	return z, true // err == io.EOF => scan consumed all content of r
+}
+
+// SetBytes interprets buf as the bytes of a big-endian unsigned
+// integer, sets z to that value, and returns z.
+func (z *Int) SetBytes(buf []byte) *Int {
+	z.abs = z.abs.setBytes(buf)
+	z.neg = false
+	return z
+}
+
+// Bytes returns the absolute value of x as a big-endian byte slice.
+//
+// To use a fixed length slice, or a preallocated one, use FillBytes.
+func (x *Int) Bytes() []byte {
+	buf := make([]byte, len(x.abs)*_S)
+	return buf[x.abs.bytes(buf):]
+}
+
+// FillBytes sets buf to the absolute value of x, storing it as a zero-extended
+// big-endian byte slice, and returns buf.
+//
+// If the absolute value of x doesn't fit in buf, FillBytes will panic.
+func (x *Int) FillBytes(buf []byte) []byte {
+	// Clear whole buffer. (This gets optimized into a memclr.)
+	for i := range buf {
+		buf[i] = 0
+	}
+	x.abs.bytes(buf)
+	return buf
+}
+
+// BitLen returns the length of the absolute value of x in bits.
+// The bit length of 0 is 0.
+func (x *Int) BitLen() int {
+	return x.abs.bitLen()
+}
+
+// TrailingZeroBits returns the number of consecutive least significant zero
+// bits of |x|.
+func (x *Int) TrailingZeroBits() uint {
+	return x.abs.trailingZeroBits()
+}
+
+// Exp sets z = x**y mod |m| (i.e. the sign of m is ignored), and returns z.
+// If m == nil or m == 0, z = x**y unless y <= 0 then z = 1. If m != 0, y < 0,
+// and x and m are not relatively prime, z is unchanged and nil is returned.
+//
+// Modular exponentiation of inputs of a particular size is not a
+// cryptographically constant-time operation.
+func (z *Int) Exp(x, y, m *Int) *Int {
+	// See Knuth, volume 2, section 4.6.3.
+	xWords := x.abs
+	if y.neg {
+		if m == nil || len(m.abs) == 0 {
+			return z.SetInt64(1)
+		}
+		// for y < 0: x**y mod m == (x**(-1))**|y| mod m
+		inverse := new(Int).ModInverse(x, m)
+		if inverse == nil {
+			return nil
+		}
+		xWords = inverse.abs
+	}
+	yWords := y.abs
+
+	var mWords nat
+	if m != nil {
+		mWords = m.abs // m.abs may be nil for m == 0
+	}
+
+	z.abs = z.abs.expNN(xWords, yWords, mWords)
+	z.neg = len(z.abs) > 0 && x.neg && len(yWords) > 0 && yWords[0]&1 == 1 // 0 has no sign
+	if z.neg && len(mWords) > 0 {
+		// make modulus result positive
+		z.abs = z.abs.sub(mWords, z.abs) // z == x**y mod |m| && 0 <= z < |m|
+		z.neg = false
+	}
+
+	return z
+}
+
+// GCD sets z to the greatest common divisor of a and b and returns z.
+// If x or y are not nil, GCD sets their value such that z = a*x + b*y.
+//
+// a and b may be positive, zero or negative. (Before Go 1.14 both had
+// to be > 0.) Regardless of the signs of a and b, z is always >= 0.
+//
+// If a == b == 0, GCD sets z = x = y = 0.
+//
+// If a == 0 and b != 0, GCD sets z = |b|, x = 0, y = sign(b) * 1.
+//
+// If a != 0 and b == 0, GCD sets z = |a|, x = sign(a) * 1, y = 0.
+func (z *Int) GCD(x, y, a, b *Int) *Int {
+	if len(a.abs) == 0 || len(b.abs) == 0 {
+		lenA, lenB, negA, negB := len(a.abs), len(b.abs), a.neg, b.neg
+		if lenA == 0 {
+			z.Set(b)
+		} else {
+			z.Set(a)
+		}
+		z.neg = false
+		if x != nil {
+			if lenA == 0 {
+				x.SetUint64(0)
+			} else {
+				x.SetUint64(1)
+				x.neg = negA
+			}
+		}
+		if y != nil {
+			if lenB == 0 {
+				y.SetUint64(0)
+			} else {
+				y.SetUint64(1)
+				y.neg = negB
+			}
+		}
+		return z
+	}
+
+	return z.lehmerGCD(x, y, a, b)
+}
+
+// lehmerSimulate attempts to simulate several Euclidean update steps
+// using the leading digits of A and B.  It returns u0, u1, v0, v1
+// such that A and B can be updated as:
+//		A = u0*A + v0*B
+//		B = u1*A + v1*B
+// Requirements: A >= B and len(B.abs) >= 2
+// Since we are calculating with full words to avoid overflow,
+// we use 'even' to track the sign of the cosequences.
+// For even iterations: u0, v1 >= 0 && u1, v0 <= 0
+// For odd  iterations: u0, v1 <= 0 && u1, v0 >= 0
+func lehmerSimulate(A, B *Int) (u0, u1, v0, v1 Word, even bool) {
+	// initialize the digits
+	var a1, a2, u2, v2 Word
+
+	m := len(B.abs) // m >= 2
+	n := len(A.abs) // n >= m >= 2
+
+	// extract the top Word of bits from A and B
+	h := nlz(A.abs[n-1])
+	a1 = A.abs[n-1]<<h | A.abs[n-2]>>(_W-h)
+	// B may have implicit zero words in the high bits if the lengths differ
+	switch {
+	case n == m:
+		a2 = B.abs[n-1]<<h | B.abs[n-2]>>(_W-h)
+	case n == m+1:
+		a2 = B.abs[n-2] >> (_W - h)
+	default:
+		a2 = 0
+	}
+
+	// Since we are calculating with full words to avoid overflow,
+	// we use 'even' to track the sign of the cosequences.
+	// For even iterations: u0, v1 >= 0 && u1, v0 <= 0
+	// For odd  iterations: u0, v1 <= 0 && u1, v0 >= 0
+	// The first iteration starts with k=1 (odd).
+	even = false
+	// variables to track the cosequences
+	u0, u1, u2 = 0, 1, 0
+	v0, v1, v2 = 0, 0, 1
+
+	// Calculate the quotient and cosequences using Collins' stopping condition.
+	// Note that overflow of a Word is not possible when computing the remainder
+	// sequence and cosequences since the cosequence size is bounded by the input size.
+	// See section 4.2 of Jebelean for details.
+	for a2 >= v2 && a1-a2 >= v1+v2 {
+		q, r := a1/a2, a1%a2
+		a1, a2 = a2, r
+		u0, u1, u2 = u1, u2, u1+q*u2
+		v0, v1, v2 = v1, v2, v1+q*v2
+		even = !even
+	}
+	return
+}
+
+// lehmerUpdate updates the inputs A and B such that:
+//		A = u0*A + v0*B
+//		B = u1*A + v1*B
+// where the signs of u0, u1, v0, v1 are given by even
+// For even == true: u0, v1 >= 0 && u1, v0 <= 0
+// For even == false: u0, v1 <= 0 && u1, v0 >= 0
+// q, r, s, t are temporary variables to avoid allocations in the multiplication
+func lehmerUpdate(A, B, q, r, s, t *Int, u0, u1, v0, v1 Word, even bool) {
+
+	t.abs = t.abs.setWord(u0)
+	s.abs = s.abs.setWord(v0)
+	t.neg = !even
+	s.neg = even
+
+	t.Mul(A, t)
+	s.Mul(B, s)
+
+	r.abs = r.abs.setWord(u1)
+	q.abs = q.abs.setWord(v1)
+	r.neg = even
+	q.neg = !even
+
+	r.Mul(A, r)
+	q.Mul(B, q)
+
+	A.Add(t, s)
+	B.Add(r, q)
+}
+
+// euclidUpdate performs a single step of the Euclidean GCD algorithm
+// if extended is true, it also updates the cosequence Ua, Ub
+func euclidUpdate(A, B, Ua, Ub, q, r, s, t *Int, extended bool) {
+	q, r = q.QuoRem(A, B, r)
+
+	*A, *B, *r = *B, *r, *A
+
+	if extended {
+		// Ua, Ub = Ub, Ua - q*Ub
+		t.Set(Ub)
+		s.Mul(Ub, q)
+		Ub.Sub(Ua, s)
+		Ua.Set(t)
+	}
+}
+
+// lehmerGCD sets z to the greatest common divisor of a and b,
+// which both must be != 0, and returns z.
+// If x or y are not nil, their values are set such that z = a*x + b*y.
+// See Knuth, The Art of Computer Programming, Vol. 2, Section 4.5.2, Algorithm L.
+// This implementation uses the improved condition by Collins requiring only one
+// quotient and avoiding the possibility of single Word overflow.
+// See Jebelean, "Improving the multiprecision Euclidean algorithm",
+// Design and Implementation of Symbolic Computation Systems, pp 45-58.
+// The cosequences are updated according to Algorithm 10.45 from
+// Cohen et al. "Handbook of Elliptic and Hyperelliptic Curve Cryptography" pp 192.
+func (z *Int) lehmerGCD(x, y, a, b *Int) *Int {
+	var A, B, Ua, Ub *Int
+
+	A = new(Int).Abs(a)
+	B = new(Int).Abs(b)
+
+	extended := x != nil || y != nil
+
+	if extended {
+		// Ua (Ub) tracks how many times input a has been accumulated into A (B).
+		Ua = new(Int).SetInt64(1)
+		Ub = new(Int)
+	}
+
+	// temp variables for multiprecision update
+	q := new(Int)
+	r := new(Int)
+	s := new(Int)
+	t := new(Int)
+
+	// ensure A >= B
+	if A.abs.cmp(B.abs) < 0 {
+		A, B = B, A
+		Ub, Ua = Ua, Ub
+	}
+
+	// loop invariant A >= B
+	for len(B.abs) > 1 {
+		// Attempt to calculate in single-precision using leading words of A and B.
+		u0, u1, v0, v1, even := lehmerSimulate(A, B)
+
+		// multiprecision Step
+		if v0 != 0 {
+			// Simulate the effect of the single-precision steps using the cosequences.
+			// A = u0*A + v0*B
+			// B = u1*A + v1*B
+			lehmerUpdate(A, B, q, r, s, t, u0, u1, v0, v1, even)
+
+			if extended {
+				// Ua = u0*Ua + v0*Ub
+				// Ub = u1*Ua + v1*Ub
+				lehmerUpdate(Ua, Ub, q, r, s, t, u0, u1, v0, v1, even)
+			}
+
+		} else {
+			// Single-digit calculations failed to simulate any quotients.
+			// Do a standard Euclidean step.
+			euclidUpdate(A, B, Ua, Ub, q, r, s, t, extended)
+		}
+	}
+
+	if len(B.abs) > 0 {
+		// extended Euclidean algorithm base case if B is a single Word
+		if len(A.abs) > 1 {
+			// A is longer than a single Word, so one update is needed.
+			euclidUpdate(A, B, Ua, Ub, q, r, s, t, extended)
+		}
+		if len(B.abs) > 0 {
+			// A and B are both a single Word.
+			aWord, bWord := A.abs[0], B.abs[0]
+			if extended {
+				var ua, ub, va, vb Word
+				ua, ub = 1, 0
+				va, vb = 0, 1
+				even := true
+				for bWord != 0 {
+					q, r := aWord/bWord, aWord%bWord
+					aWord, bWord = bWord, r
+					ua, ub = ub, ua+q*ub
+					va, vb = vb, va+q*vb
+					even = !even
+				}
+
+				t.abs = t.abs.setWord(ua)
+				s.abs = s.abs.setWord(va)
+				t.neg = !even
+				s.neg = even
+
+				t.Mul(Ua, t)
+				s.Mul(Ub, s)
+
+				Ua.Add(t, s)
+			} else {
+				for bWord != 0 {
+					aWord, bWord = bWord, aWord%bWord
+				}
+			}
+			A.abs[0] = aWord
+		}
+	}
+	negA := a.neg
+	if y != nil {
+		// avoid aliasing b needed in the division below
+		if y == b {
+			B.Set(b)
+		} else {
+			B = b
+		}
+		// y = (z - a*x)/b
+		y.Mul(a, Ua) // y can safely alias a
+		if negA {
+			y.neg = !y.neg
+		}
+		y.Sub(A, y)
+		y.Div(y, B)
+	}
+
+	if x != nil {
+		*x = *Ua
+		if negA {
+			x.neg = !x.neg
+		}
+	}
+
+	*z = *A
+
+	return z
+}
+
+// Rand sets z to a pseudo-random number in [0, n) and returns z.
+//
+// As this uses the math/rand package, it must not be used for
+// security-sensitive work. Use crypto/rand.Int instead.
+func (z *Int) Rand(rnd *rand.Rand, n *Int) *Int {
+	z.neg = false
+	if n.neg || len(n.abs) == 0 {
+		z.abs = nil
+		return z
+	}
+	z.abs = z.abs.random(rnd, n.abs, n.abs.bitLen())
+	return z
+}
+
+// ModInverse sets z to the multiplicative inverse of g in the ring ℤ/nℤ
+// and returns z. If g and n are not relatively prime, g has no multiplicative
+// inverse in the ring ℤ/nℤ.  In this case, z is unchanged and the return value
+// is nil.
+func (z *Int) ModInverse(g, n *Int) *Int {
+	// GCD expects parameters a and b to be > 0.
+	if n.neg {
+		var n2 Int
+		n = n2.Neg(n)
+	}
+	if g.neg {
+		var g2 Int
+		g = g2.Mod(g, n)
+	}
+	var d, x Int
+	d.GCD(&x, nil, g, n)
+
+	// if and only if d==1, g and n are relatively prime
+	if d.Cmp(intOne) != 0 {
+		return nil
+	}
+
+	// x and y are such that g*x + n*y = 1, therefore x is the inverse element,
+	// but it may be negative, so convert to the range 0 <= z < |n|
+	if x.neg {
+		z.Add(&x, n)
+	} else {
+		z.Set(&x)
+	}
+	return z
+}
+
+// Jacobi returns the Jacobi symbol (x/y), either +1, -1, or 0.
+// The y argument must be an odd integer.
+func Jacobi(x, y *Int) int {
+	if len(y.abs) == 0 || y.abs[0]&1 == 0 {
+		panic(fmt.Sprintf("big: invalid 2nd argument to Int.Jacobi: need odd integer but got %s", y))
+	}
+
+	// We use the formulation described in chapter 2, section 2.4,
+	// "The Yacas Book of Algorithms":
+	// http://yacas.sourceforge.net/Algo.book.pdf
+
+	var a, b, c Int
+	a.Set(x)
+	b.Set(y)
+	j := 1
+
+	if b.neg {
+		if a.neg {
+			j = -1
+		}
+		b.neg = false
+	}
+
+	for {
+		if b.Cmp(intOne) == 0 {
+			return j
+		}
+		if len(a.abs) == 0 {
+			return 0
+		}
+		a.Mod(&a, &b)
+		if len(a.abs) == 0 {
+			return 0
+		}
+		// a > 0
+
+		// handle factors of 2 in 'a'
+		s := a.abs.trailingZeroBits()
+		if s&1 != 0 {
+			bmod8 := b.abs[0] & 7
+			if bmod8 == 3 || bmod8 == 5 {
+				j = -j
+			}
+		}
+		c.Rsh(&a, s) // a = 2^s*c
+
+		// swap numerator and denominator
+		if b.abs[0]&3 == 3 && c.abs[0]&3 == 3 {
+			j = -j
+		}
+		a.Set(&b)
+		b.Set(&c)
+	}
+}
+
+// modSqrt3Mod4 uses the identity
+//      (a^((p+1)/4))^2  mod p
+//   == u^(p+1)          mod p
+//   == u^2              mod p
+// to calculate the square root of any quadratic residue mod p quickly for 3
+// mod 4 primes.
+func (z *Int) modSqrt3Mod4Prime(x, p *Int) *Int {
+	e := new(Int).Add(p, intOne) // e = p + 1
+	e.Rsh(e, 2)                  // e = (p + 1) / 4
+	z.Exp(x, e, p)               // z = x^e mod p
+	return z
+}
+
+// modSqrt5Mod8 uses Atkin's observation that 2 is not a square mod p
+//   alpha ==  (2*a)^((p-5)/8)    mod p
+//   beta  ==  2*a*alpha^2        mod p  is a square root of -1
+//   b     ==  a*alpha*(beta-1)   mod p  is a square root of a
+// to calculate the square root of any quadratic residue mod p quickly for 5
+// mod 8 primes.
+func (z *Int) modSqrt5Mod8Prime(x, p *Int) *Int {
+	// p == 5 mod 8 implies p = e*8 + 5
+	// e is the quotient and 5 the remainder on division by 8
+	e := new(Int).Rsh(p, 3)  // e = (p - 5) / 8
+	tx := new(Int).Lsh(x, 1) // tx = 2*x
+	alpha := new(Int).Exp(tx, e, p)
+	beta := new(Int).Mul(alpha, alpha)
+	beta.Mod(beta, p)
+	beta.Mul(beta, tx)
+	beta.Mod(beta, p)
+	beta.Sub(beta, intOne)
+	beta.Mul(beta, x)
+	beta.Mod(beta, p)
+	beta.Mul(beta, alpha)
+	z.Mod(beta, p)
+	return z
+}
+
+// modSqrtTonelliShanks uses the Tonelli-Shanks algorithm to find the square
+// root of a quadratic residue modulo any prime.
+func (z *Int) modSqrtTonelliShanks(x, p *Int) *Int {
+	// Break p-1 into s*2^e such that s is odd.
+	var s Int
+	s.Sub(p, intOne)
+	e := s.abs.trailingZeroBits()
+	s.Rsh(&s, e)
+
+	// find some non-square n
+	var n Int
+	n.SetInt64(2)
+	for Jacobi(&n, p) != -1 {
+		n.Add(&n, intOne)
+	}
+
+	// Core of the Tonelli-Shanks algorithm. Follows the description in
+	// section 6 of "Square roots from 1; 24, 51, 10 to Dan Shanks" by Ezra
+	// Brown:
+	// https://www.maa.org/sites/default/files/pdf/upload_library/22/Polya/07468342.di020786.02p0470a.pdf
+	var y, b, g, t Int
+	y.Add(&s, intOne)
+	y.Rsh(&y, 1)
+	y.Exp(x, &y, p)  // y = x^((s+1)/2)
+	b.Exp(x, &s, p)  // b = x^s
+	g.Exp(&n, &s, p) // g = n^s
+	r := e
+	for {
+		// find the least m such that ord_p(b) = 2^m
+		var m uint
+		t.Set(&b)
+		for t.Cmp(intOne) != 0 {
+			t.Mul(&t, &t).Mod(&t, p)
+			m++
+		}
+
+		if m == 0 {
+			return z.Set(&y)
+		}
+
+		t.SetInt64(0).SetBit(&t, int(r-m-1), 1).Exp(&g, &t, p)
+		// t = g^(2^(r-m-1)) mod p
+		g.Mul(&t, &t).Mod(&g, p) // g = g^(2^(r-m)) mod p
+		y.Mul(&y, &t).Mod(&y, p)
+		b.Mul(&b, &g).Mod(&b, p)
+		r = m
+	}
+}
+
+// ModSqrt sets z to a square root of x mod p if such a square root exists, and
+// returns z. The modulus p must be an odd prime. If x is not a square mod p,
+// ModSqrt leaves z unchanged and returns nil. This function panics if p is
+// not an odd integer.
+func (z *Int) ModSqrt(x, p *Int) *Int {
+	switch Jacobi(x, p) {
+	case -1:
+		return nil // x is not a square mod p
+	case 0:
+		return z.SetInt64(0) // sqrt(0) mod p = 0
+	case 1:
+		break
+	}
+	if x.neg || x.Cmp(p) >= 0 { // ensure 0 <= x < p
+		x = new(Int).Mod(x, p)
+	}
+
+	switch {
+	case p.abs[0]%4 == 3:
+		// Check whether p is 3 mod 4, and if so, use the faster algorithm.
+		return z.modSqrt3Mod4Prime(x, p)
+	case p.abs[0]%8 == 5:
+		// Check whether p is 5 mod 8, use Atkin's algorithm.
+		return z.modSqrt5Mod8Prime(x, p)
+	default:
+		// Otherwise, use Tonelli-Shanks.
+		return z.modSqrtTonelliShanks(x, p)
+	}
+}
+
+// Lsh sets z = x << n and returns z.
+func (z *Int) Lsh(x *Int, n uint) *Int {
+	z.abs = z.abs.shl(x.abs, n)
+	z.neg = x.neg
+	return z
+}
+
+// Rsh sets z = x >> n and returns z.
+func (z *Int) Rsh(x *Int, n uint) *Int {
+	if x.neg {
+		// (-x) >> s == ^(x-1) >> s == ^((x-1) >> s) == -(((x-1) >> s) + 1)
+		t := z.abs.sub(x.abs, natOne) // no underflow because |x| > 0
+		t = t.shr(t, n)
+		z.abs = t.add(t, natOne)
+		z.neg = true // z cannot be zero if x is negative
+		return z
+	}
+
+	z.abs = z.abs.shr(x.abs, n)
+	z.neg = false
+	return z
+}
+
+// Bit returns the value of the i'th bit of x. That is, it
+// returns (x>>i)&1. The bit index i must be >= 0.
+func (x *Int) Bit(i int) uint {
+	if i == 0 {
+		// optimization for common case: odd/even test of x
+		if len(x.abs) > 0 {
+			return uint(x.abs[0] & 1) // bit 0 is same for -x
+		}
+		return 0
+	}
+	if i < 0 {
+		panic("negative bit index")
+	}
+	if x.neg {
+		t := nat(nil).sub(x.abs, natOne)
+		return t.bit(uint(i)) ^ 1
+	}
+
+	return x.abs.bit(uint(i))
+}
+
+// SetBit sets z to x, with x's i'th bit set to b (0 or 1).
+// That is, if b is 1 SetBit sets z = x | (1 << i);
+// if b is 0 SetBit sets z = x &^ (1 << i). If b is not 0 or 1,
+// SetBit will panic.
+func (z *Int) SetBit(x *Int, i int, b uint) *Int {
+	if i < 0 {
+		panic("negative bit index")
+	}
+	if x.neg {
+		t := z.abs.sub(x.abs, natOne)
+		t = t.setBit(t, uint(i), b^1)
+		z.abs = t.add(t, natOne)
+		z.neg = len(z.abs) > 0
+		return z
+	}
+	z.abs = z.abs.setBit(x.abs, uint(i), b)
+	z.neg = false
+	return z
+}
+
+// And sets z = x & y and returns z.
+func (z *Int) And(x, y *Int) *Int {
+	if x.neg == y.neg {
+		if x.neg {
+			// (-x) & (-y) == ^(x-1) & ^(y-1) == ^((x-1) | (y-1)) == -(((x-1) | (y-1)) + 1)
+			x1 := nat(nil).sub(x.abs, natOne)
+			y1 := nat(nil).sub(y.abs, natOne)
+			z.abs = z.abs.add(z.abs.or(x1, y1), natOne)
+			z.neg = true // z cannot be zero if x and y are negative
+			return z
+		}
+
+		// x & y == x & y
+		z.abs = z.abs.and(x.abs, y.abs)
+		z.neg = false
+		return z
+	}
+
+	// x.neg != y.neg
+	if x.neg {
+		x, y = y, x // & is symmetric
+	}
+
+	// x & (-y) == x & ^(y-1) == x &^ (y-1)
+	y1 := nat(nil).sub(y.abs, natOne)
+	z.abs = z.abs.andNot(x.abs, y1)
+	z.neg = false
+	return z
+}
+
+// AndNot sets z = x &^ y and returns z.
+func (z *Int) AndNot(x, y *Int) *Int {
+	if x.neg == y.neg {
+		if x.neg {
+			// (-x) &^ (-y) == ^(x-1) &^ ^(y-1) == ^(x-1) & (y-1) == (y-1) &^ (x-1)
+			x1 := nat(nil).sub(x.abs, natOne)
+			y1 := nat(nil).sub(y.abs, natOne)
+			z.abs = z.abs.andNot(y1, x1)
+			z.neg = false
+			return z
+		}
+
+		// x &^ y == x &^ y
+		z.abs = z.abs.andNot(x.abs, y.abs)
+		z.neg = false
+		return z
+	}
+
+	if x.neg {
+		// (-x) &^ y == ^(x-1) &^ y == ^(x-1) & ^y == ^((x-1) | y) == -(((x-1) | y) + 1)
+		x1 := nat(nil).sub(x.abs, natOne)
+		z.abs = z.abs.add(z.abs.or(x1, y.abs), natOne)
+		z.neg = true // z cannot be zero if x is negative and y is positive
+		return z
+	}
+
+	// x &^ (-y) == x &^ ^(y-1) == x & (y-1)
+	y1 := nat(nil).sub(y.abs, natOne)
+	z.abs = z.abs.and(x.abs, y1)
+	z.neg = false
+	return z
+}
+
+// Or sets z = x | y and returns z.
+func (z *Int) Or(x, y *Int) *Int {
+	if x.neg == y.neg {
+		if x.neg {
+			// (-x) | (-y) == ^(x-1) | ^(y-1) == ^((x-1) & (y-1)) == -(((x-1) & (y-1)) + 1)
+			x1 := nat(nil).sub(x.abs, natOne)
+			y1 := nat(nil).sub(y.abs, natOne)
+			z.abs = z.abs.add(z.abs.and(x1, y1), natOne)
+			z.neg = true // z cannot be zero if x and y are negative
+			return z
+		}
+
+		// x | y == x | y
+		z.abs = z.abs.or(x.abs, y.abs)
+		z.neg = false
+		return z
+	}
+
+	// x.neg != y.neg
+	if x.neg {
+		x, y = y, x // | is symmetric
+	}
+
+	// x | (-y) == x | ^(y-1) == ^((y-1) &^ x) == -(^((y-1) &^ x) + 1)
+	y1 := nat(nil).sub(y.abs, natOne)
+	z.abs = z.abs.add(z.abs.andNot(y1, x.abs), natOne)
+	z.neg = true // z cannot be zero if one of x or y is negative
+	return z
+}
+
+// Xor sets z = x ^ y and returns z.
+func (z *Int) Xor(x, y *Int) *Int {
+	if x.neg == y.neg {
+		if x.neg {
+			// (-x) ^ (-y) == ^(x-1) ^ ^(y-1) == (x-1) ^ (y-1)
+			x1 := nat(nil).sub(x.abs, natOne)
+			y1 := nat(nil).sub(y.abs, natOne)
+			z.abs = z.abs.xor(x1, y1)
+			z.neg = false
+			return z
+		}
+
+		// x ^ y == x ^ y
+		z.abs = z.abs.xor(x.abs, y.abs)
+		z.neg = false
+		return z
+	}
+
+	// x.neg != y.neg
+	if x.neg {
+		x, y = y, x // ^ is symmetric
+	}
+
+	// x ^ (-y) == x ^ ^(y-1) == ^(x ^ (y-1)) == -((x ^ (y-1)) + 1)
+	y1 := nat(nil).sub(y.abs, natOne)
+	z.abs = z.abs.add(z.abs.xor(x.abs, y1), natOne)
+	z.neg = true // z cannot be zero if only one of x or y is negative
+	return z
+}
+
+// Not sets z = ^x and returns z.
+func (z *Int) Not(x *Int) *Int {
+	if x.neg {
+		// ^(-x) == ^(^(x-1)) == x-1
+		z.abs = z.abs.sub(x.abs, natOne)
+		z.neg = false
+		return z
+	}
+
+	// ^x == -x-1 == -(x+1)
+	z.abs = z.abs.add(x.abs, natOne)
+	z.neg = true // z cannot be zero if x is positive
+	return z
+}
+
+// Sqrt sets z to ⌊√x⌋, the largest integer such that z² ≤ x, and returns z.
+// It panics if x is negative.
+func (z *Int) Sqrt(x *Int) *Int {
+	if x.neg {
+		panic("square root of negative number")
+	}
+	z.neg = false
+	z.abs = z.abs.sqrt(x.abs)
+	return z
+}
diff --git a/contrib/go/_std_1.18/src/math/big/intconv.go b/contrib/go/_std_1.18/src/math/big/intconv.go
new file mode 100644
index 0000000000..0567284105
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/intconv.go
@@ -0,0 +1,257 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements int-to-string conversion functions.
+
+package big
+
+import (
+	"errors"
+	"fmt"
+	"io"
+)
+
+// Text returns the string representation of x in the given base.
+// Base must be between 2 and 62, inclusive. The result uses the
+// lower-case letters 'a' to 'z' for digit values 10 to 35, and
+// the upper-case letters 'A' to 'Z' for digit values 36 to 61.
+// No prefix (such as "0x") is added to the string. If x is a nil
+// pointer it returns "<nil>".
+func (x *Int) Text(base int) string {
+	if x == nil {
+		return "<nil>"
+	}
+	return string(x.abs.itoa(x.neg, base))
+}
+
+// Append appends the string representation of x, as generated by
+// x.Text(base), to buf and returns the extended buffer.
+func (x *Int) Append(buf []byte, base int) []byte {
+	if x == nil {
+		return append(buf, "<nil>"...)
+	}
+	return append(buf, x.abs.itoa(x.neg, base)...)
+}
+
+// String returns the decimal representation of x as generated by
+// x.Text(10).
+func (x *Int) String() string {
+	return x.Text(10)
+}
+
+// write count copies of text to s
+func writeMultiple(s fmt.State, text string, count int) {
+	if len(text) > 0 {
+		b := []byte(text)
+		for ; count > 0; count-- {
+			s.Write(b)
+		}
+	}
+}
+
+var _ fmt.Formatter = intOne // *Int must implement fmt.Formatter
+
+// Format implements fmt.Formatter. It accepts the formats
+// 'b' (binary), 'o' (octal with 0 prefix), 'O' (octal with 0o prefix),
+// 'd' (decimal), 'x' (lowercase hexadecimal), and
+// 'X' (uppercase hexadecimal).
+// Also supported are the full suite of package fmt's format
+// flags for integral types, including '+' and ' ' for sign
+// control, '#' for leading zero in octal and for hexadecimal,
+// a leading "0x" or "0X" for "%#x" and "%#X" respectively,
+// specification of minimum digits precision, output field
+// width, space or zero padding, and '-' for left or right
+// justification.
+//
+func (x *Int) Format(s fmt.State, ch rune) {
+	// determine base
+	var base int
+	switch ch {
+	case 'b':
+		base = 2
+	case 'o', 'O':
+		base = 8
+	case 'd', 's', 'v':
+		base = 10
+	case 'x', 'X':
+		base = 16
+	default:
+		// unknown format
+		fmt.Fprintf(s, "%%!%c(big.Int=%s)", ch, x.String())
+		return
+	}
+
+	if x == nil {
+		fmt.Fprint(s, "<nil>")
+		return
+	}
+
+	// determine sign character
+	sign := ""
+	switch {
+	case x.neg:
+		sign = "-"
+	case s.Flag('+'): // supersedes ' ' when both specified
+		sign = "+"
+	case s.Flag(' '):
+		sign = " "
+	}
+
+	// determine prefix characters for indicating output base
+	prefix := ""
+	if s.Flag('#') {
+		switch ch {
+		case 'b': // binary
+			prefix = "0b"
+		case 'o': // octal
+			prefix = "0"
+		case 'x': // hexadecimal
+			prefix = "0x"
+		case 'X':
+			prefix = "0X"
+		}
+	}
+	if ch == 'O' {
+		prefix = "0o"
+	}
+
+	digits := x.abs.utoa(base)
+	if ch == 'X' {
+		// faster than bytes.ToUpper
+		for i, d := range digits {
+			if 'a' <= d && d <= 'z' {
+				digits[i] = 'A' + (d - 'a')
+			}
+		}
+	}
+
+	// number of characters for the three classes of number padding
+	var left int  // space characters to left of digits for right justification ("%8d")
+	var zeros int // zero characters (actually cs[0]) as left-most digits ("%.8d")
+	var right int // space characters to right of digits for left justification ("%-8d")
+
+	// determine number padding from precision: the least number of digits to output
+	precision, precisionSet := s.Precision()
+	if precisionSet {
+		switch {
+		case len(digits) < precision:
+			zeros = precision - len(digits) // count of zero padding
+		case len(digits) == 1 && digits[0] == '0' && precision == 0:
+			return // print nothing if zero value (x == 0) and zero precision ("." or ".0")
+		}
+	}
+
+	// determine field pad from width: the least number of characters to output
+	length := len(sign) + len(prefix) + zeros + len(digits)
+	if width, widthSet := s.Width(); widthSet && length < width { // pad as specified
+		switch d := width - length; {
+		case s.Flag('-'):
+			// pad on the right with spaces; supersedes '0' when both specified
+			right = d
+		case s.Flag('0') && !precisionSet:
+			// pad with zeros unless precision also specified
+			zeros = d
+		default:
+			// pad on the left with spaces
+			left = d
+		}
+	}
+
+	// print number as [left pad][sign][prefix][zero pad][digits][right pad]
+	writeMultiple(s, " ", left)
+	writeMultiple(s, sign, 1)
+	writeMultiple(s, prefix, 1)
+	writeMultiple(s, "0", zeros)
+	s.Write(digits)
+	writeMultiple(s, " ", right)
+}
+
+// scan sets z to the integer value corresponding to the longest possible prefix
+// read from r representing a signed integer number in a given conversion base.
+// It returns z, the actual conversion base used, and an error, if any. In the
+// error case, the value of z is undefined but the returned value is nil. The
+// syntax follows the syntax of integer literals in Go.
+//
+// The base argument must be 0 or a value from 2 through MaxBase. If the base
+// is 0, the string prefix determines the actual conversion base. A prefix of
+// ``0b'' or ``0B'' selects base 2; a ``0'', ``0o'', or ``0O'' prefix selects
+// base 8, and a ``0x'' or ``0X'' prefix selects base 16. Otherwise the selected
+// base is 10.
+//
+func (z *Int) scan(r io.ByteScanner, base int) (*Int, int, error) {
+	// determine sign
+	neg, err := scanSign(r)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	// determine mantissa
+	z.abs, base, _, err = z.abs.scan(r, base, false)
+	if err != nil {
+		return nil, base, err
+	}
+	z.neg = len(z.abs) > 0 && neg // 0 has no sign
+
+	return z, base, nil
+}
+
+func scanSign(r io.ByteScanner) (neg bool, err error) {
+	var ch byte
+	if ch, err = r.ReadByte(); err != nil {
+		return false, err
+	}
+	switch ch {
+	case '-':
+		neg = true
+	case '+':
+		// nothing to do
+	default:
+		r.UnreadByte()
+	}
+	return
+}
+
+// byteReader is a local wrapper around fmt.ScanState;
+// it implements the ByteReader interface.
+type byteReader struct {
+	fmt.ScanState
+}
+
+func (r byteReader) ReadByte() (byte, error) {
+	ch, size, err := r.ReadRune()
+	if size != 1 && err == nil {
+		err = fmt.Errorf("invalid rune %#U", ch)
+	}
+	return byte(ch), err
+}
+
+func (r byteReader) UnreadByte() error {
+	return r.UnreadRune()
+}
+
+var _ fmt.Scanner = intOne // *Int must implement fmt.Scanner
+
+// Scan is a support routine for fmt.Scanner; it sets z to the value of
+// the scanned number. It accepts the formats 'b' (binary), 'o' (octal),
+// 'd' (decimal), 'x' (lowercase hexadecimal), and 'X' (uppercase hexadecimal).
+func (z *Int) Scan(s fmt.ScanState, ch rune) error {
+	s.SkipSpace() // skip leading space characters
+	base := 0
+	switch ch {
+	case 'b':
+		base = 2
+	case 'o':
+		base = 8
+	case 'd':
+		base = 10
+	case 'x', 'X':
+		base = 16
+	case 's', 'v':
+		// let scan determine the base
+	default:
+		return errors.New("Int.Scan: invalid verb")
+	}
+	_, _, err := z.scan(byteReader{s}, base)
+	return err
+}
diff --git a/contrib/go/_std_1.18/src/math/big/intmarsh.go b/contrib/go/_std_1.18/src/math/big/intmarsh.go
new file mode 100644
index 0000000000..c1422e2710
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/intmarsh.go
@@ -0,0 +1,80 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements encoding/decoding of Ints.
+
+package big
+
+import (
+	"bytes"
+	"fmt"
+)
+
+// Gob codec version. Permits backward-compatible changes to the encoding.
+const intGobVersion byte = 1
+
+// GobEncode implements the gob.GobEncoder interface.
+func (x *Int) GobEncode() ([]byte, error) {
+	if x == nil {
+		return nil, nil
+	}
+	buf := make([]byte, 1+len(x.abs)*_S) // extra byte for version and sign bit
+	i := x.abs.bytes(buf) - 1            // i >= 0
+	b := intGobVersion << 1              // make space for sign bit
+	if x.neg {
+		b |= 1
+	}
+	buf[i] = b
+	return buf[i:], nil
+}
+
+// GobDecode implements the gob.GobDecoder interface.
+func (z *Int) GobDecode(buf []byte) error {
+	if len(buf) == 0 {
+		// Other side sent a nil or default value.
+		*z = Int{}
+		return nil
+	}
+	b := buf[0]
+	if b>>1 != intGobVersion {
+		return fmt.Errorf("Int.GobDecode: encoding version %d not supported", b>>1)
+	}
+	z.neg = b&1 != 0
+	z.abs = z.abs.setBytes(buf[1:])
+	return nil
+}
+
+// MarshalText implements the encoding.TextMarshaler interface.
+func (x *Int) MarshalText() (text []byte, err error) {
+	if x == nil {
+		return []byte("<nil>"), nil
+	}
+	return x.abs.itoa(x.neg, 10), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface.
+func (z *Int) UnmarshalText(text []byte) error {
+	if _, ok := z.setFromScanner(bytes.NewReader(text), 0); !ok {
+		return fmt.Errorf("math/big: cannot unmarshal %q into a *big.Int", text)
+	}
+	return nil
+}
+
+// The JSON marshalers are only here for API backward compatibility
+// (programs that explicitly look for these two methods). JSON works
+// fine with the TextMarshaler only.
+
+// MarshalJSON implements the json.Marshaler interface.
+func (x *Int) MarshalJSON() ([]byte, error) {
+	return x.MarshalText()
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface.
+func (z *Int) UnmarshalJSON(text []byte) error {
+	// Ignore null, like in the main JSON package.
+	if string(text) == "null" {
+		return nil
+	}
+	return z.UnmarshalText(text)
+}
diff --git a/contrib/go/_std_1.18/src/math/big/nat.go b/contrib/go/_std_1.18/src/math/big/nat.go
new file mode 100644
index 0000000000..140c619c8c
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/nat.go
@@ -0,0 +1,1244 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements unsigned multi-precision integers (natural
+// numbers). They are the building blocks for the implementation
+// of signed integers, rationals, and floating-point numbers.
+//
+// Caution: This implementation relies on the function "alias"
+//          which assumes that (nat) slice capacities are never
+//          changed (no 3-operand slice expressions). If that
+//          changes, alias needs to be updated for correctness.
+
+package big
+
+import (
+	"encoding/binary"
+	"math/bits"
+	"math/rand"
+	"sync"
+)
+
+// An unsigned integer x of the form
+//
+//   x = x[n-1]*_B^(n-1) + x[n-2]*_B^(n-2) + ... + x[1]*_B + x[0]
+//
+// with 0 <= x[i] < _B and 0 <= i < n is stored in a slice of length n,
+// with the digits x[i] as the slice elements.
+//
+// A number is normalized if the slice contains no leading 0 digits.
+// During arithmetic operations, denormalized values may occur but are
+// always normalized before returning the final result. The normalized
+// representation of 0 is the empty or nil slice (length = 0).
+//
+type nat []Word
+
+var (
+	natOne  = nat{1}
+	natTwo  = nat{2}
+	natFive = nat{5}
+	natTen  = nat{10}
+)
+
+func (z nat) clear() {
+	for i := range z {
+		z[i] = 0
+	}
+}
+
+func (z nat) norm() nat {
+	i := len(z)
+	for i > 0 && z[i-1] == 0 {
+		i--
+	}
+	return z[0:i]
+}
+
+func (z nat) make(n int) nat {
+	if n <= cap(z) {
+		return z[:n] // reuse z
+	}
+	if n == 1 {
+		// Most nats start small and stay that way; don't over-allocate.
+		return make(nat, 1)
+	}
+	// Choosing a good value for e has significant performance impact
+	// because it increases the chance that a value can be reused.
+	const e = 4 // extra capacity
+	return make(nat, n, n+e)
+}
+
+func (z nat) setWord(x Word) nat {
+	if x == 0 {
+		return z[:0]
+	}
+	z = z.make(1)
+	z[0] = x
+	return z
+}
+
+func (z nat) setUint64(x uint64) nat {
+	// single-word value
+	if w := Word(x); uint64(w) == x {
+		return z.setWord(w)
+	}
+	// 2-word value
+	z = z.make(2)
+	z[1] = Word(x >> 32)
+	z[0] = Word(x)
+	return z
+}
+
+func (z nat) set(x nat) nat {
+	z = z.make(len(x))
+	copy(z, x)
+	return z
+}
+
+func (z nat) add(x, y nat) nat {
+	m := len(x)
+	n := len(y)
+
+	switch {
+	case m < n:
+		return z.add(y, x)
+	case m == 0:
+		// n == 0 because m >= n; result is 0
+		return z[:0]
+	case n == 0:
+		// result is x
+		return z.set(x)
+	}
+	// m > 0
+
+	z = z.make(m + 1)
+	c := addVV(z[0:n], x, y)
+	if m > n {
+		c = addVW(z[n:m], x[n:], c)
+	}
+	z[m] = c
+
+	return z.norm()
+}
+
+func (z nat) sub(x, y nat) nat {
+	m := len(x)
+	n := len(y)
+
+	switch {
+	case m < n:
+		panic("underflow")
+	case m == 0:
+		// n == 0 because m >= n; result is 0
+		return z[:0]
+	case n == 0:
+		// result is x
+		return z.set(x)
+	}
+	// m > 0
+
+	z = z.make(m)
+	c := subVV(z[0:n], x, y)
+	if m > n {
+		c = subVW(z[n:], x[n:], c)
+	}
+	if c != 0 {
+		panic("underflow")
+	}
+
+	return z.norm()
+}
+
+func (x nat) cmp(y nat) (r int) {
+	m := len(x)
+	n := len(y)
+	if m != n || m == 0 {
+		switch {
+		case m < n:
+			r = -1
+		case m > n:
+			r = 1
+		}
+		return
+	}
+
+	i := m - 1
+	for i > 0 && x[i] == y[i] {
+		i--
+	}
+
+	switch {
+	case x[i] < y[i]:
+		r = -1
+	case x[i] > y[i]:
+		r = 1
+	}
+	return
+}
+
+func (z nat) mulAddWW(x nat, y, r Word) nat {
+	m := len(x)
+	if m == 0 || y == 0 {
+		return z.setWord(r) // result is r
+	}
+	// m > 0
+
+	z = z.make(m + 1)
+	z[m] = mulAddVWW(z[0:m], x, y, r)
+
+	return z.norm()
+}
+
+// basicMul multiplies x and y and leaves the result in z.
+// The (non-normalized) result is placed in z[0 : len(x) + len(y)].
+func basicMul(z, x, y nat) {
+	z[0 : len(x)+len(y)].clear() // initialize z
+	for i, d := range y {
+		if d != 0 {
+			z[len(x)+i] = addMulVVW(z[i:i+len(x)], x, d)
+		}
+	}
+}
+
+// montgomery computes z mod m = x*y*2**(-n*_W) mod m,
+// assuming k = -1/m mod 2**_W.
+// z is used for storing the result which is returned;
+// z must not alias x, y or m.
+// See Gueron, "Efficient Software Implementations of Modular Exponentiation".
+// https://eprint.iacr.org/2011/239.pdf
+// In the terminology of that paper, this is an "Almost Montgomery Multiplication":
+// x and y are required to satisfy 0 <= z < 2**(n*_W) and then the result
+// z is guaranteed to satisfy 0 <= z < 2**(n*_W), but it may not be < m.
+func (z nat) montgomery(x, y, m nat, k Word, n int) nat {
+	// This code assumes x, y, m are all the same length, n.
+	// (required by addMulVVW and the for loop).
+	// It also assumes that x, y are already reduced mod m,
+	// or else the result will not be properly reduced.
+	if len(x) != n || len(y) != n || len(m) != n {
+		panic("math/big: mismatched montgomery number lengths")
+	}
+	z = z.make(n * 2)
+	z.clear()
+	var c Word
+	for i := 0; i < n; i++ {
+		d := y[i]
+		c2 := addMulVVW(z[i:n+i], x, d)
+		t := z[i] * k
+		c3 := addMulVVW(z[i:n+i], m, t)
+		cx := c + c2
+		cy := cx + c3
+		z[n+i] = cy
+		if cx < c2 || cy < c3 {
+			c = 1
+		} else {
+			c = 0
+		}
+	}
+	if c != 0 {
+		subVV(z[:n], z[n:], m)
+	} else {
+		copy(z[:n], z[n:])
+	}
+	return z[:n]
+}
+
+// Fast version of z[0:n+n>>1].add(z[0:n+n>>1], x[0:n]) w/o bounds checks.
+// Factored out for readability - do not use outside karatsuba.
+func karatsubaAdd(z, x nat, n int) {
+	if c := addVV(z[0:n], z, x); c != 0 {
+		addVW(z[n:n+n>>1], z[n:], c)
+	}
+}
+
+// Like karatsubaAdd, but does subtract.
+func karatsubaSub(z, x nat, n int) {
+	if c := subVV(z[0:n], z, x); c != 0 {
+		subVW(z[n:n+n>>1], z[n:], c)
+	}
+}
+
+// Operands that are shorter than karatsubaThreshold are multiplied using
+// "grade school" multiplication; for longer operands the Karatsuba algorithm
+// is used.
+var karatsubaThreshold = 40 // computed by calibrate_test.go
+
+// karatsuba multiplies x and y and leaves the result in z.
+// Both x and y must have the same length n and n must be a
+// power of 2. The result vector z must have len(z) >= 6*n.
+// The (non-normalized) result is placed in z[0 : 2*n].
+func karatsuba(z, x, y nat) {
+	n := len(y)
+
+	// Switch to basic multiplication if numbers are odd or small.
+	// (n is always even if karatsubaThreshold is even, but be
+	// conservative)
+	if n&1 != 0 || n < karatsubaThreshold || n < 2 {
+		basicMul(z, x, y)
+		return
+	}
+	// n&1 == 0 && n >= karatsubaThreshold && n >= 2
+
+	// Karatsuba multiplication is based on the observation that
+	// for two numbers x and y with:
+	//
+	//   x = x1*b + x0
+	//   y = y1*b + y0
+	//
+	// the product x*y can be obtained with 3 products z2, z1, z0
+	// instead of 4:
+	//
+	//   x*y = x1*y1*b*b + (x1*y0 + x0*y1)*b + x0*y0
+	//       =    z2*b*b +              z1*b +    z0
+	//
+	// with:
+	//
+	//   xd = x1 - x0
+	//   yd = y0 - y1
+	//
+	//   z1 =      xd*yd                    + z2 + z0
+	//      = (x1-x0)*(y0 - y1)             + z2 + z0
+	//      = x1*y0 - x1*y1 - x0*y0 + x0*y1 + z2 + z0
+	//      = x1*y0 -    z2 -    z0 + x0*y1 + z2 + z0
+	//      = x1*y0                 + x0*y1
+
+	// split x, y into "digits"
+	n2 := n >> 1              // n2 >= 1
+	x1, x0 := x[n2:], x[0:n2] // x = x1*b + y0
+	y1, y0 := y[n2:], y[0:n2] // y = y1*b + y0
+
+	// z is used for the result and temporary storage:
+	//
+	//   6*n     5*n     4*n     3*n     2*n     1*n     0*n
+	// z = [z2 copy|z0 copy| xd*yd | yd:xd | x1*y1 | x0*y0 ]
+	//
+	// For each recursive call of karatsuba, an unused slice of
+	// z is passed in that has (at least) half the length of the
+	// caller's z.
+
+	// compute z0 and z2 with the result "in place" in z
+	karatsuba(z, x0, y0)     // z0 = x0*y0
+	karatsuba(z[n:], x1, y1) // z2 = x1*y1
+
+	// compute xd (or the negative value if underflow occurs)
+	s := 1 // sign of product xd*yd
+	xd := z[2*n : 2*n+n2]
+	if subVV(xd, x1, x0) != 0 { // x1-x0
+		s = -s
+		subVV(xd, x0, x1) // x0-x1
+	}
+
+	// compute yd (or the negative value if underflow occurs)
+	yd := z[2*n+n2 : 3*n]
+	if subVV(yd, y0, y1) != 0 { // y0-y1
+		s = -s
+		subVV(yd, y1, y0) // y1-y0
+	}
+
+	// p = (x1-x0)*(y0-y1) == x1*y0 - x1*y1 - x0*y0 + x0*y1 for s > 0
+	// p = (x0-x1)*(y0-y1) == x0*y0 - x0*y1 - x1*y0 + x1*y1 for s < 0
+	p := z[n*3:]
+	karatsuba(p, xd, yd)
+
+	// save original z2:z0
+	// (ok to use upper half of z since we're done recursing)
+	r := z[n*4:]
+	copy(r, z[:n*2])
+
+	// add up all partial products
+	//
+	//   2*n     n     0
+	// z = [ z2  | z0  ]
+	//   +    [ z0  ]
+	//   +    [ z2  ]
+	//   +    [  p  ]
+	//
+	karatsubaAdd(z[n2:], r, n)
+	karatsubaAdd(z[n2:], r[n:], n)
+	if s > 0 {
+		karatsubaAdd(z[n2:], p, n)
+	} else {
+		karatsubaSub(z[n2:], p, n)
+	}
+}
+
+// alias reports whether x and y share the same base array.
+// Note: alias assumes that the capacity of underlying arrays
+//       is never changed for nat values; i.e. that there are
+//       no 3-operand slice expressions in this code (or worse,
+//       reflect-based operations to the same effect).
+func alias(x, y nat) bool {
+	return cap(x) > 0 && cap(y) > 0 && &x[0:cap(x)][cap(x)-1] == &y[0:cap(y)][cap(y)-1]
+}
+
+// addAt implements z += x<<(_W*i); z must be long enough.
+// (we don't use nat.add because we need z to stay the same
+// slice, and we don't need to normalize z after each addition)
+func addAt(z, x nat, i int) {
+	if n := len(x); n > 0 {
+		if c := addVV(z[i:i+n], z[i:], x); c != 0 {
+			j := i + n
+			if j < len(z) {
+				addVW(z[j:], z[j:], c)
+			}
+		}
+	}
+}
+
+func max(x, y int) int {
+	if x > y {
+		return x
+	}
+	return y
+}
+
+// karatsubaLen computes an approximation to the maximum k <= n such that
+// k = p<<i for a number p <= threshold and an i >= 0. Thus, the
+// result is the largest number that can be divided repeatedly by 2 before
+// becoming about the value of threshold.
+func karatsubaLen(n, threshold int) int {
+	i := uint(0)
+	for n > threshold {
+		n >>= 1
+		i++
+	}
+	return n << i
+}
+
+func (z nat) mul(x, y nat) nat {
+	m := len(x)
+	n := len(y)
+
+	switch {
+	case m < n:
+		return z.mul(y, x)
+	case m == 0 || n == 0:
+		return z[:0]
+	case n == 1:
+		return z.mulAddWW(x, y[0], 0)
+	}
+	// m >= n > 1
+
+	// determine if z can be reused
+	if alias(z, x) || alias(z, y) {
+		z = nil // z is an alias for x or y - cannot reuse
+	}
+
+	// use basic multiplication if the numbers are small
+	if n < karatsubaThreshold {
+		z = z.make(m + n)
+		basicMul(z, x, y)
+		return z.norm()
+	}
+	// m >= n && n >= karatsubaThreshold && n >= 2
+
+	// determine Karatsuba length k such that
+	//
+	//   x = xh*b + x0  (0 <= x0 < b)
+	//   y = yh*b + y0  (0 <= y0 < b)
+	//   b = 1<<(_W*k)  ("base" of digits xi, yi)
+	//
+	k := karatsubaLen(n, karatsubaThreshold)
+	// k <= n
+
+	// multiply x0 and y0 via Karatsuba
+	x0 := x[0:k]              // x0 is not normalized
+	y0 := y[0:k]              // y0 is not normalized
+	z = z.make(max(6*k, m+n)) // enough space for karatsuba of x0*y0 and full result of x*y
+	karatsuba(z, x0, y0)
+	z = z[0 : m+n]  // z has final length but may be incomplete
+	z[2*k:].clear() // upper portion of z is garbage (and 2*k <= m+n since k <= n <= m)
+
+	// If xh != 0 or yh != 0, add the missing terms to z. For
+	//
+	//   xh = xi*b^i + ... + x2*b^2 + x1*b (0 <= xi < b)
+	//   yh =                         y1*b (0 <= y1 < b)
+	//
+	// the missing terms are
+	//
+	//   x0*y1*b and xi*y0*b^i, xi*y1*b^(i+1) for i > 0
+	//
+	// since all the yi for i > 1 are 0 by choice of k: If any of them
+	// were > 0, then yh >= b^2 and thus y >= b^2. Then k' = k*2 would
+	// be a larger valid threshold contradicting the assumption about k.
+	//
+	if k < n || m != n {
+		tp := getNat(3 * k)
+		t := *tp
+
+		// add x0*y1*b
+		x0 := x0.norm()
+		y1 := y[k:]       // y1 is normalized because y is
+		t = t.mul(x0, y1) // update t so we don't lose t's underlying array
+		addAt(z, t, k)
+
+		// add xi*y0<<i, xi*y1*b<<(i+k)
+		y0 := y0.norm()
+		for i := k; i < len(x); i += k {
+			xi := x[i:]
+			if len(xi) > k {
+				xi = xi[:k]
+			}
+			xi = xi.norm()
+			t = t.mul(xi, y0)
+			addAt(z, t, i)
+			t = t.mul(xi, y1)
+			addAt(z, t, i+k)
+		}
+
+		putNat(tp)
+	}
+
+	return z.norm()
+}
+
+// basicSqr sets z = x*x and is asymptotically faster than basicMul
+// by about a factor of 2, but slower for small arguments due to overhead.
+// Requirements: len(x) > 0, len(z) == 2*len(x)
+// The (non-normalized) result is placed in z.
+func basicSqr(z, x nat) {
+	n := len(x)
+	tp := getNat(2 * n)
+	t := *tp // temporary variable to hold the products
+	t.clear()
+	z[1], z[0] = mulWW(x[0], x[0]) // the initial square
+	for i := 1; i < n; i++ {
+		d := x[i]
+		// z collects the squares x[i] * x[i]
+		z[2*i+1], z[2*i] = mulWW(d, d)
+		// t collects the products x[i] * x[j] where j < i
+		t[2*i] = addMulVVW(t[i:2*i], x[0:i], d)
+	}
+	t[2*n-1] = shlVU(t[1:2*n-1], t[1:2*n-1], 1) // double the j < i products
+	addVV(z, z, t)                              // combine the result
+	putNat(tp)
+}
+
+// karatsubaSqr squares x and leaves the result in z.
+// len(x) must be a power of 2 and len(z) >= 6*len(x).
+// The (non-normalized) result is placed in z[0 : 2*len(x)].
+//
+// The algorithm and the layout of z are the same as for karatsuba.
+func karatsubaSqr(z, x nat) {
+	n := len(x)
+
+	if n&1 != 0 || n < karatsubaSqrThreshold || n < 2 {
+		basicSqr(z[:2*n], x)
+		return
+	}
+
+	n2 := n >> 1
+	x1, x0 := x[n2:], x[0:n2]
+
+	karatsubaSqr(z, x0)
+	karatsubaSqr(z[n:], x1)
+
+	// s = sign(xd*yd) == -1 for xd != 0; s == 1 for xd == 0
+	xd := z[2*n : 2*n+n2]
+	if subVV(xd, x1, x0) != 0 {
+		subVV(xd, x0, x1)
+	}
+
+	p := z[n*3:]
+	karatsubaSqr(p, xd)
+
+	r := z[n*4:]
+	copy(r, z[:n*2])
+
+	karatsubaAdd(z[n2:], r, n)
+	karatsubaAdd(z[n2:], r[n:], n)
+	karatsubaSub(z[n2:], p, n) // s == -1 for p != 0; s == 1 for p == 0
+}
+
+// Operands that are shorter than basicSqrThreshold are squared using
+// "grade school" multiplication; for operands longer than karatsubaSqrThreshold
+// we use the Karatsuba algorithm optimized for x == y.
+var basicSqrThreshold = 20      // computed by calibrate_test.go
+var karatsubaSqrThreshold = 260 // computed by calibrate_test.go
+
+// z = x*x
+func (z nat) sqr(x nat) nat {
+	n := len(x)
+	switch {
+	case n == 0:
+		return z[:0]
+	case n == 1:
+		d := x[0]
+		z = z.make(2)
+		z[1], z[0] = mulWW(d, d)
+		return z.norm()
+	}
+
+	if alias(z, x) {
+		z = nil // z is an alias for x - cannot reuse
+	}
+
+	if n < basicSqrThreshold {
+		z = z.make(2 * n)
+		basicMul(z, x, x)
+		return z.norm()
+	}
+	if n < karatsubaSqrThreshold {
+		z = z.make(2 * n)
+		basicSqr(z, x)
+		return z.norm()
+	}
+
+	// Use Karatsuba multiplication optimized for x == y.
+	// The algorithm and layout of z are the same as for mul.
+
+	// z = (x1*b + x0)^2 = x1^2*b^2 + 2*x1*x0*b + x0^2
+
+	k := karatsubaLen(n, karatsubaSqrThreshold)
+
+	x0 := x[0:k]
+	z = z.make(max(6*k, 2*n))
+	karatsubaSqr(z, x0) // z = x0^2
+	z = z[0 : 2*n]
+	z[2*k:].clear()
+
+	if k < n {
+		tp := getNat(2 * k)
+		t := *tp
+		x0 := x0.norm()
+		x1 := x[k:]
+		t = t.mul(x0, x1)
+		addAt(z, t, k)
+		addAt(z, t, k) // z = 2*x1*x0*b + x0^2
+		t = t.sqr(x1)
+		addAt(z, t, 2*k) // z = x1^2*b^2 + 2*x1*x0*b + x0^2
+		putNat(tp)
+	}
+
+	return z.norm()
+}
+
+// mulRange computes the product of all the unsigned integers in the
+// range [a, b] inclusively. If a > b (empty range), the result is 1.
+func (z nat) mulRange(a, b uint64) nat {
+	switch {
+	case a == 0:
+		// cut long ranges short (optimization)
+		return z.setUint64(0)
+	case a > b:
+		return z.setUint64(1)
+	case a == b:
+		return z.setUint64(a)
+	case a+1 == b:
+		return z.mul(nat(nil).setUint64(a), nat(nil).setUint64(b))
+	}
+	m := (a + b) / 2
+	return z.mul(nat(nil).mulRange(a, m), nat(nil).mulRange(m+1, b))
+}
+
+// getNat returns a *nat of len n. The contents may not be zero.
+// The pool holds *nat to avoid allocation when converting to interface{}.
+func getNat(n int) *nat {
+	var z *nat
+	if v := natPool.Get(); v != nil {
+		z = v.(*nat)
+	}
+	if z == nil {
+		z = new(nat)
+	}
+	*z = z.make(n)
+	return z
+}
+
+func putNat(x *nat) {
+	natPool.Put(x)
+}
+
+var natPool sync.Pool
+
+// Length of x in bits. x must be normalized.
+func (x nat) bitLen() int {
+	if i := len(x) - 1; i >= 0 {
+		return i*_W + bits.Len(uint(x[i]))
+	}
+	return 0
+}
+
+// trailingZeroBits returns the number of consecutive least significant zero
+// bits of x.
+func (x nat) trailingZeroBits() uint {
+	if len(x) == 0 {
+		return 0
+	}
+	var i uint
+	for x[i] == 0 {
+		i++
+	}
+	// x[i] != 0
+	return i*_W + uint(bits.TrailingZeros(uint(x[i])))
+}
+
+func same(x, y nat) bool {
+	return len(x) == len(y) && len(x) > 0 && &x[0] == &y[0]
+}
+
+// z = x << s
+func (z nat) shl(x nat, s uint) nat {
+	if s == 0 {
+		if same(z, x) {
+			return z
+		}
+		if !alias(z, x) {
+			return z.set(x)
+		}
+	}
+
+	m := len(x)
+	if m == 0 {
+		return z[:0]
+	}
+	// m > 0
+
+	n := m + int(s/_W)
+	z = z.make(n + 1)
+	z[n] = shlVU(z[n-m:n], x, s%_W)
+	z[0 : n-m].clear()
+
+	return z.norm()
+}
+
+// z = x >> s
+func (z nat) shr(x nat, s uint) nat {
+	if s == 0 {
+		if same(z, x) {
+			return z
+		}
+		if !alias(z, x) {
+			return z.set(x)
+		}
+	}
+
+	m := len(x)
+	n := m - int(s/_W)
+	if n <= 0 {
+		return z[:0]
+	}
+	// n > 0
+
+	z = z.make(n)
+	shrVU(z, x[m-n:], s%_W)
+
+	return z.norm()
+}
+
+func (z nat) setBit(x nat, i uint, b uint) nat {
+	j := int(i / _W)
+	m := Word(1) << (i % _W)
+	n := len(x)
+	switch b {
+	case 0:
+		z = z.make(n)
+		copy(z, x)
+		if j >= n {
+			// no need to grow
+			return z
+		}
+		z[j] &^= m
+		return z.norm()
+	case 1:
+		if j >= n {
+			z = z.make(j + 1)
+			z[n:].clear()
+		} else {
+			z = z.make(n)
+		}
+		copy(z, x)
+		z[j] |= m
+		// no need to normalize
+		return z
+	}
+	panic("set bit is not 0 or 1")
+}
+
+// bit returns the value of the i'th bit, with lsb == bit 0.
+func (x nat) bit(i uint) uint {
+	j := i / _W
+	if j >= uint(len(x)) {
+		return 0
+	}
+	// 0 <= j < len(x)
+	return uint(x[j] >> (i % _W) & 1)
+}
+
+// sticky returns 1 if there's a 1 bit within the
+// i least significant bits, otherwise it returns 0.
+func (x nat) sticky(i uint) uint {
+	j := i / _W
+	if j >= uint(len(x)) {
+		if len(x) == 0 {
+			return 0
+		}
+		return 1
+	}
+	// 0 <= j < len(x)
+	for _, x := range x[:j] {
+		if x != 0 {
+			return 1
+		}
+	}
+	if x[j]<<(_W-i%_W) != 0 {
+		return 1
+	}
+	return 0
+}
+
+func (z nat) and(x, y nat) nat {
+	m := len(x)
+	n := len(y)
+	if m > n {
+		m = n
+	}
+	// m <= n
+
+	z = z.make(m)
+	for i := 0; i < m; i++ {
+		z[i] = x[i] & y[i]
+	}
+
+	return z.norm()
+}
+
+func (z nat) andNot(x, y nat) nat {
+	m := len(x)
+	n := len(y)
+	if n > m {
+		n = m
+	}
+	// m >= n
+
+	z = z.make(m)
+	for i := 0; i < n; i++ {
+		z[i] = x[i] &^ y[i]
+	}
+	copy(z[n:m], x[n:m])
+
+	return z.norm()
+}
+
+func (z nat) or(x, y nat) nat {
+	m := len(x)
+	n := len(y)
+	s := x
+	if m < n {
+		n, m = m, n
+		s = y
+	}
+	// m >= n
+
+	z = z.make(m)
+	for i := 0; i < n; i++ {
+		z[i] = x[i] | y[i]
+	}
+	copy(z[n:m], s[n:m])
+
+	return z.norm()
+}
+
+func (z nat) xor(x, y nat) nat {
+	m := len(x)
+	n := len(y)
+	s := x
+	if m < n {
+		n, m = m, n
+		s = y
+	}
+	// m >= n
+
+	z = z.make(m)
+	for i := 0; i < n; i++ {
+		z[i] = x[i] ^ y[i]
+	}
+	copy(z[n:m], s[n:m])
+
+	return z.norm()
+}
+
+// random creates a random integer in [0..limit), using the space in z if
+// possible. n is the bit length of limit.
+func (z nat) random(rand *rand.Rand, limit nat, n int) nat {
+	if alias(z, limit) {
+		z = nil // z is an alias for limit - cannot reuse
+	}
+	z = z.make(len(limit))
+
+	bitLengthOfMSW := uint(n % _W)
+	if bitLengthOfMSW == 0 {
+		bitLengthOfMSW = _W
+	}
+	mask := Word((1 << bitLengthOfMSW) - 1)
+
+	for {
+		switch _W {
+		case 32:
+			for i := range z {
+				z[i] = Word(rand.Uint32())
+			}
+		case 64:
+			for i := range z {
+				z[i] = Word(rand.Uint32()) | Word(rand.Uint32())<<32
+			}
+		default:
+			panic("unknown word size")
+		}
+		z[len(limit)-1] &= mask
+		if z.cmp(limit) < 0 {
+			break
+		}
+	}
+
+	return z.norm()
+}
+
+// If m != 0 (i.e., len(m) != 0), expNN sets z to x**y mod m;
+// otherwise it sets z to x**y. The result is the value of z.
+func (z nat) expNN(x, y, m nat) nat {
+	if alias(z, x) || alias(z, y) {
+		// We cannot allow in-place modification of x or y.
+		z = nil
+	}
+
+	// x**y mod 1 == 0
+	if len(m) == 1 && m[0] == 1 {
+		return z.setWord(0)
+	}
+	// m == 0 || m > 1
+
+	// x**0 == 1
+	if len(y) == 0 {
+		return z.setWord(1)
+	}
+	// y > 0
+
+	// x**1 mod m == x mod m
+	if len(y) == 1 && y[0] == 1 && len(m) != 0 {
+		_, z = nat(nil).div(z, x, m)
+		return z
+	}
+	// y > 1
+
+	if len(m) != 0 {
+		// We likely end up being as long as the modulus.
+		z = z.make(len(m))
+	}
+	z = z.set(x)
+
+	// If the base is non-trivial and the exponent is large, we use
+	// 4-bit, windowed exponentiation. This involves precomputing 14 values
+	// (x^2...x^15) but then reduces the number of multiply-reduces by a
+	// third. Even for a 32-bit exponent, this reduces the number of
+	// operations. Uses Montgomery method for odd moduli.
+	if x.cmp(natOne) > 0 && len(y) > 1 && len(m) > 0 {
+		if m[0]&1 == 1 {
+			return z.expNNMontgomery(x, y, m)
+		}
+		return z.expNNWindowed(x, y, m)
+	}
+
+	v := y[len(y)-1] // v > 0 because y is normalized and y > 0
+	shift := nlz(v) + 1
+	v <<= shift
+	var q nat
+
+	const mask = 1 << (_W - 1)
+
+	// We walk through the bits of the exponent one by one. Each time we
+	// see a bit, we square, thus doubling the power. If the bit is a one,
+	// we also multiply by x, thus adding one to the power.
+
+	w := _W - int(shift)
+	// zz and r are used to avoid allocating in mul and div as
+	// otherwise the arguments would alias.
+	var zz, r nat
+	for j := 0; j < w; j++ {
+		zz = zz.sqr(z)
+		zz, z = z, zz
+
+		if v&mask != 0 {
+			zz = zz.mul(z, x)
+			zz, z = z, zz
+		}
+
+		if len(m) != 0 {
+			zz, r = zz.div(r, z, m)
+			zz, r, q, z = q, z, zz, r
+		}
+
+		v <<= 1
+	}
+
+	for i := len(y) - 2; i >= 0; i-- {
+		v = y[i]
+
+		for j := 0; j < _W; j++ {
+			zz = zz.sqr(z)
+			zz, z = z, zz
+
+			if v&mask != 0 {
+				zz = zz.mul(z, x)
+				zz, z = z, zz
+			}
+
+			if len(m) != 0 {
+				zz, r = zz.div(r, z, m)
+				zz, r, q, z = q, z, zz, r
+			}
+
+			v <<= 1
+		}
+	}
+
+	return z.norm()
+}
+
+// expNNWindowed calculates x**y mod m using a fixed, 4-bit window.
+func (z nat) expNNWindowed(x, y, m nat) nat {
+	// zz and r are used to avoid allocating in mul and div as otherwise
+	// the arguments would alias.
+	var zz, r nat
+
+	const n = 4
+	// powers[i] contains x^i.
+	var powers [1 << n]nat
+	powers[0] = natOne
+	powers[1] = x
+	for i := 2; i < 1<<n; i += 2 {
+		p2, p, p1 := &powers[i/2], &powers[i], &powers[i+1]
+		*p = p.sqr(*p2)
+		zz, r = zz.div(r, *p, m)
+		*p, r = r, *p
+		*p1 = p1.mul(*p, x)
+		zz, r = zz.div(r, *p1, m)
+		*p1, r = r, *p1
+	}
+
+	z = z.setWord(1)
+
+	for i := len(y) - 1; i >= 0; i-- {
+		yi := y[i]
+		for j := 0; j < _W; j += n {
+			if i != len(y)-1 || j != 0 {
+				// Unrolled loop for significant performance
+				// gain. Use go test -bench=".*" in crypto/rsa
+				// to check performance before making changes.
+				zz = zz.sqr(z)
+				zz, z = z, zz
+				zz, r = zz.div(r, z, m)
+				z, r = r, z
+
+				zz = zz.sqr(z)
+				zz, z = z, zz
+				zz, r = zz.div(r, z, m)
+				z, r = r, z
+
+				zz = zz.sqr(z)
+				zz, z = z, zz
+				zz, r = zz.div(r, z, m)
+				z, r = r, z
+
+				zz = zz.sqr(z)
+				zz, z = z, zz
+				zz, r = zz.div(r, z, m)
+				z, r = r, z
+			}
+
+			zz = zz.mul(z, powers[yi>>(_W-n)])
+			zz, z = z, zz
+			zz, r = zz.div(r, z, m)
+			z, r = r, z
+
+			yi <<= n
+		}
+	}
+
+	return z.norm()
+}
+
+// expNNMontgomery calculates x**y mod m using a fixed, 4-bit window.
+// Uses Montgomery representation.
+func (z nat) expNNMontgomery(x, y, m nat) nat {
+	numWords := len(m)
+
+	// We want the lengths of x and m to be equal.
+	// It is OK if x >= m as long as len(x) == len(m).
+	if len(x) > numWords {
+		_, x = nat(nil).div(nil, x, m)
+		// Note: now len(x) <= numWords, not guaranteed ==.
+	}
+	if len(x) < numWords {
+		rr := make(nat, numWords)
+		copy(rr, x)
+		x = rr
+	}
+
+	// Ideally the precomputations would be performed outside, and reused
+	// k0 = -m**-1 mod 2**_W. Algorithm from: Dumas, J.G. "On Newton–Raphson
+	// Iteration for Multiplicative Inverses Modulo Prime Powers".
+	k0 := 2 - m[0]
+	t := m[0] - 1
+	for i := 1; i < _W; i <<= 1 {
+		t *= t
+		k0 *= (t + 1)
+	}
+	k0 = -k0
+
+	// RR = 2**(2*_W*len(m)) mod m
+	RR := nat(nil).setWord(1)
+	zz := nat(nil).shl(RR, uint(2*numWords*_W))
+	_, RR = nat(nil).div(RR, zz, m)
+	if len(RR) < numWords {
+		zz = zz.make(numWords)
+		copy(zz, RR)
+		RR = zz
+	}
+	// one = 1, with equal length to that of m
+	one := make(nat, numWords)
+	one[0] = 1
+
+	const n = 4
+	// powers[i] contains x^i
+	var powers [1 << n]nat
+	powers[0] = powers[0].montgomery(one, RR, m, k0, numWords)
+	powers[1] = powers[1].montgomery(x, RR, m, k0, numWords)
+	for i := 2; i < 1<<n; i++ {
+		powers[i] = powers[i].montgomery(powers[i-1], powers[1], m, k0, numWords)
+	}
+
+	// initialize z = 1 (Montgomery 1)
+	z = z.make(numWords)
+	copy(z, powers[0])
+
+	zz = zz.make(numWords)
+
+	// same windowed exponent, but with Montgomery multiplications
+	for i := len(y) - 1; i >= 0; i-- {
+		yi := y[i]
+		for j := 0; j < _W; j += n {
+			if i != len(y)-1 || j != 0 {
+				zz = zz.montgomery(z, z, m, k0, numWords)
+				z = z.montgomery(zz, zz, m, k0, numWords)
+				zz = zz.montgomery(z, z, m, k0, numWords)
+				z = z.montgomery(zz, zz, m, k0, numWords)
+			}
+			zz = zz.montgomery(z, powers[yi>>(_W-n)], m, k0, numWords)
+			z, zz = zz, z
+			yi <<= n
+		}
+	}
+	// convert to regular number
+	zz = zz.montgomery(z, one, m, k0, numWords)
+
+	// One last reduction, just in case.
+	// See golang.org/issue/13907.
+	if zz.cmp(m) >= 0 {
+		// Common case is m has high bit set; in that case,
+		// since zz is the same length as m, there can be just
+		// one multiple of m to remove. Just subtract.
+		// We think that the subtract should be sufficient in general,
+		// so do that unconditionally, but double-check,
+		// in case our beliefs are wrong.
+		// The div is not expected to be reached.
+		zz = zz.sub(zz, m)
+		if zz.cmp(m) >= 0 {
+			_, zz = nat(nil).div(nil, zz, m)
+		}
+	}
+
+	return zz.norm()
+}
+
+// bytes writes the value of z into buf using big-endian encoding.
+// The value of z is encoded in the slice buf[i:]. If the value of z
+// cannot be represented in buf, bytes panics. The number i of unused
+// bytes at the beginning of buf is returned as result.
+func (z nat) bytes(buf []byte) (i int) {
+	i = len(buf)
+	for _, d := range z {
+		for j := 0; j < _S; j++ {
+			i--
+			if i >= 0 {
+				buf[i] = byte(d)
+			} else if byte(d) != 0 {
+				panic("math/big: buffer too small to fit value")
+			}
+			d >>= 8
+		}
+	}
+
+	if i < 0 {
+		i = 0
+	}
+	for i < len(buf) && buf[i] == 0 {
+		i++
+	}
+
+	return
+}
+
+// bigEndianWord returns the contents of buf interpreted as a big-endian encoded Word value.
+func bigEndianWord(buf []byte) Word {
+	if _W == 64 {
+		return Word(binary.BigEndian.Uint64(buf))
+	}
+	return Word(binary.BigEndian.Uint32(buf))
+}
+
+// setBytes interprets buf as the bytes of a big-endian unsigned
+// integer, sets z to that value, and returns z.
+func (z nat) setBytes(buf []byte) nat {
+	z = z.make((len(buf) + _S - 1) / _S)
+
+	i := len(buf)
+	for k := 0; i >= _S; k++ {
+		z[k] = bigEndianWord(buf[i-_S : i])
+		i -= _S
+	}
+	if i > 0 {
+		var d Word
+		for s := uint(0); i > 0; s += 8 {
+			d |= Word(buf[i-1]) << s
+			i--
+		}
+		z[len(z)-1] = d
+	}
+
+	return z.norm()
+}
+
+// sqrt sets z = ⌊√x⌋
+func (z nat) sqrt(x nat) nat {
+	if x.cmp(natOne) <= 0 {
+		return z.set(x)
+	}
+	if alias(z, x) {
+		z = nil
+	}
+
+	// Start with value known to be too large and repeat "z = ⌊(z + ⌊x/z⌋)/2⌋" until it stops getting smaller.
+	// See Brent and Zimmermann, Modern Computer Arithmetic, Algorithm 1.13 (SqrtInt).
+	// https://members.loria.fr/PZimmermann/mca/pub226.html
+	// If x is one less than a perfect square, the sequence oscillates between the correct z and z+1;
+	// otherwise it converges to the correct z and stays there.
+	var z1, z2 nat
+	z1 = z
+	z1 = z1.setUint64(1)
+	z1 = z1.shl(z1, uint(x.bitLen()+1)/2) // must be ≥ √x
+	for n := 0; ; n++ {
+		z2, _ = z2.div(nil, x, z1)
+		z2 = z2.add(z2, z1)
+		z2 = z2.shr(z2, 1)
+		if z2.cmp(z1) >= 0 {
+			// z1 is answer.
+			// Figure out whether z1 or z2 is currently aliased to z by looking at loop count.
+			if n&1 == 0 {
+				return z1
+			}
+			return z.set(z1)
+		}
+		z1, z2 = z2, z1
+	}
+}
diff --git a/contrib/go/_std_1.18/src/math/big/natconv.go b/contrib/go/_std_1.18/src/math/big/natconv.go
new file mode 100644
index 0000000000..42d1cccf6f
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/natconv.go
@@ -0,0 +1,512 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements nat-to-string conversion functions.
+
+package big
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"math/bits"
+	"sync"
+)
+
+const digits = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+
+// Note: MaxBase = len(digits), but it must remain an untyped rune constant
+//       for API compatibility.
+
+// MaxBase is the largest number base accepted for string conversions.
+const MaxBase = 10 + ('z' - 'a' + 1) + ('Z' - 'A' + 1)
+const maxBaseSmall = 10 + ('z' - 'a' + 1)
+
+// maxPow returns (b**n, n) such that b**n is the largest power b**n <= _M.
+// For instance maxPow(10) == (1e19, 19) for 19 decimal digits in a 64bit Word.
+// In other words, at most n digits in base b fit into a Word.
+// TODO(gri) replace this with a table, generated at build time.
+func maxPow(b Word) (p Word, n int) {
+	p, n = b, 1 // assuming b <= _M
+	for max := _M / b; p <= max; {
+		// p == b**n && p <= max
+		p *= b
+		n++
+	}
+	// p == b**n && p <= _M
+	return
+}
+
+// pow returns x**n for n > 0, and 1 otherwise.
+func pow(x Word, n int) (p Word) {
+	// n == sum of bi * 2**i, for 0 <= i < imax, and bi is 0 or 1
+	// thus x**n == product of x**(2**i) for all i where bi == 1
+	// (Russian Peasant Method for exponentiation)
+	p = 1
+	for n > 0 {
+		if n&1 != 0 {
+			p *= x
+		}
+		x *= x
+		n >>= 1
+	}
+	return
+}
+
+// scan errors
+var (
+	errNoDigits = errors.New("number has no digits")
+	errInvalSep = errors.New("'_' must separate successive digits")
+)
+
+// scan scans the number corresponding to the longest possible prefix
+// from r representing an unsigned number in a given conversion base.
+// scan returns the corresponding natural number res, the actual base b,
+// a digit count, and a read or syntax error err, if any.
+//
+// For base 0, an underscore character ``_'' may appear between a base
+// prefix and an adjacent digit, and between successive digits; such
+// underscores do not change the value of the number, or the returned
+// digit count. Incorrect placement of underscores is reported as an
+// error if there are no other errors. If base != 0, underscores are
+// not recognized and thus terminate scanning like any other character
+// that is not a valid radix point or digit.
+//
+//     number    = mantissa | prefix pmantissa .
+//     prefix    = "0" [ "b" | "B" | "o" | "O" | "x" | "X" ] .
+//     mantissa  = digits "." [ digits ] | digits | "." digits .
+//     pmantissa = [ "_" ] digits "." [ digits ] | [ "_" ] digits | "." digits .
+//     digits    = digit { [ "_" ] digit } .
+//     digit     = "0" ... "9" | "a" ... "z" | "A" ... "Z" .
+//
+// Unless fracOk is set, the base argument must be 0 or a value between
+// 2 and MaxBase. If fracOk is set, the base argument must be one of
+// 0, 2, 8, 10, or 16. Providing an invalid base argument leads to a run-
+// time panic.
+//
+// For base 0, the number prefix determines the actual base: A prefix of
+// ``0b'' or ``0B'' selects base 2, ``0o'' or ``0O'' selects base 8, and
+// ``0x'' or ``0X'' selects base 16. If fracOk is false, a ``0'' prefix
+// (immediately followed by digits) selects base 8 as well. Otherwise,
+// the selected base is 10 and no prefix is accepted.
+//
+// If fracOk is set, a period followed by a fractional part is permitted.
+// The result value is computed as if there were no period present; and
+// the count value is used to determine the fractional part.
+//
+// For bases <= 36, lower and upper case letters are considered the same:
+// The letters 'a' to 'z' and 'A' to 'Z' represent digit values 10 to 35.
+// For bases > 36, the upper case letters 'A' to 'Z' represent the digit
+// values 36 to 61.
+//
+// A result digit count > 0 corresponds to the number of (non-prefix) digits
+// parsed. A digit count <= 0 indicates the presence of a period (if fracOk
+// is set, only), and -count is the number of fractional digits found.
+// In this case, the actual value of the scanned number is res * b**count.
+//
+func (z nat) scan(r io.ByteScanner, base int, fracOk bool) (res nat, b, count int, err error) {
+	// reject invalid bases
+	baseOk := base == 0 ||
+		!fracOk && 2 <= base && base <= MaxBase ||
+		fracOk && (base == 2 || base == 8 || base == 10 || base == 16)
+	if !baseOk {
+		panic(fmt.Sprintf("invalid number base %d", base))
+	}
+
+	// prev encodes the previously seen char: it is one
+	// of '_', '0' (a digit), or '.' (anything else). A
+	// valid separator '_' may only occur after a digit
+	// and if base == 0.
+	prev := '.'
+	invalSep := false
+
+	// one char look-ahead
+	ch, err := r.ReadByte()
+
+	// determine actual base
+	b, prefix := base, 0
+	if base == 0 {
+		// actual base is 10 unless there's a base prefix
+		b = 10
+		if err == nil && ch == '0' {
+			prev = '0'
+			count = 1
+			ch, err = r.ReadByte()
+			if err == nil {
+				// possibly one of 0b, 0B, 0o, 0O, 0x, 0X
+				switch ch {
+				case 'b', 'B':
+					b, prefix = 2, 'b'
+				case 'o', 'O':
+					b, prefix = 8, 'o'
+				case 'x', 'X':
+					b, prefix = 16, 'x'
+				default:
+					if !fracOk {
+						b, prefix = 8, '0'
+					}
+				}
+				if prefix != 0 {
+					count = 0 // prefix is not counted
+					if prefix != '0' {
+						ch, err = r.ReadByte()
+					}
+				}
+			}
+		}
+	}
+
+	// convert string
+	// Algorithm: Collect digits in groups of at most n digits in di
+	// and then use mulAddWW for every such group to add them to the
+	// result.
+	z = z[:0]
+	b1 := Word(b)
+	bn, n := maxPow(b1) // at most n digits in base b1 fit into Word
+	di := Word(0)       // 0 <= di < b1**i < bn
+	i := 0              // 0 <= i < n
+	dp := -1            // position of decimal point
+	for err == nil {
+		if ch == '.' && fracOk {
+			fracOk = false
+			if prev == '_' {
+				invalSep = true
+			}
+			prev = '.'
+			dp = count
+		} else if ch == '_' && base == 0 {
+			if prev != '0' {
+				invalSep = true
+			}
+			prev = '_'
+		} else {
+			// convert rune into digit value d1
+			var d1 Word
+			switch {
+			case '0' <= ch && ch <= '9':
+				d1 = Word(ch - '0')
+			case 'a' <= ch && ch <= 'z':
+				d1 = Word(ch - 'a' + 10)
+			case 'A' <= ch && ch <= 'Z':
+				if b <= maxBaseSmall {
+					d1 = Word(ch - 'A' + 10)
+				} else {
+					d1 = Word(ch - 'A' + maxBaseSmall)
+				}
+			default:
+				d1 = MaxBase + 1
+			}
+			if d1 >= b1 {
+				r.UnreadByte() // ch does not belong to number anymore
+				break
+			}
+			prev = '0'
+			count++
+
+			// collect d1 in di
+			di = di*b1 + d1
+			i++
+
+			// if di is "full", add it to the result
+			if i == n {
+				z = z.mulAddWW(z, bn, di)
+				di = 0
+				i = 0
+			}
+		}
+
+		ch, err = r.ReadByte()
+	}
+
+	if err == io.EOF {
+		err = nil
+	}
+
+	// other errors take precedence over invalid separators
+	if err == nil && (invalSep || prev == '_') {
+		err = errInvalSep
+	}
+
+	if count == 0 {
+		// no digits found
+		if prefix == '0' {
+			// there was only the octal prefix 0 (possibly followed by separators and digits > 7);
+			// interpret as decimal 0
+			return z[:0], 10, 1, err
+		}
+		err = errNoDigits // fall through; result will be 0
+	}
+
+	// add remaining digits to result
+	if i > 0 {
+		z = z.mulAddWW(z, pow(b1, i), di)
+	}
+	res = z.norm()
+
+	// adjust count for fraction, if any
+	if dp >= 0 {
+		// 0 <= dp <= count
+		count = dp - count
+	}
+
+	return
+}
+
+// utoa converts x to an ASCII representation in the given base;
+// base must be between 2 and MaxBase, inclusive.
+func (x nat) utoa(base int) []byte {
+	return x.itoa(false, base)
+}
+
+// itoa is like utoa but it prepends a '-' if neg && x != 0.
+func (x nat) itoa(neg bool, base int) []byte {
+	if base < 2 || base > MaxBase {
+		panic("invalid base")
+	}
+
+	// x == 0
+	if len(x) == 0 {
+		return []byte("0")
+	}
+	// len(x) > 0
+
+	// allocate buffer for conversion
+	i := int(float64(x.bitLen())/math.Log2(float64(base))) + 1 // off by 1 at most
+	if neg {
+		i++
+	}
+	s := make([]byte, i)
+
+	// convert power of two and non power of two bases separately
+	if b := Word(base); b == b&-b {
+		// shift is base b digit size in bits
+		shift := uint(bits.TrailingZeros(uint(b))) // shift > 0 because b >= 2
+		mask := Word(1<<shift - 1)
+		w := x[0]         // current word
+		nbits := uint(_W) // number of unprocessed bits in w
+
+		// convert less-significant words (include leading zeros)
+		for k := 1; k < len(x); k++ {
+			// convert full digits
+			for nbits >= shift {
+				i--
+				s[i] = digits[w&mask]
+				w >>= shift
+				nbits -= shift
+			}
+
+			// convert any partial leading digit and advance to next word
+			if nbits == 0 {
+				// no partial digit remaining, just advance
+				w = x[k]
+				nbits = _W
+			} else {
+				// partial digit in current word w (== x[k-1]) and next word x[k]
+				w |= x[k] << nbits
+				i--
+				s[i] = digits[w&mask]
+
+				// advance
+				w = x[k] >> (shift - nbits)
+				nbits = _W - (shift - nbits)
+			}
+		}
+
+		// convert digits of most-significant word w (omit leading zeros)
+		for w != 0 {
+			i--
+			s[i] = digits[w&mask]
+			w >>= shift
+		}
+
+	} else {
+		bb, ndigits := maxPow(b)
+
+		// construct table of successive squares of bb*leafSize to use in subdivisions
+		// result (table != nil) <=> (len(x) > leafSize > 0)
+		table := divisors(len(x), b, ndigits, bb)
+
+		// preserve x, create local copy for use by convertWords
+		q := nat(nil).set(x)
+
+		// convert q to string s in base b
+		q.convertWords(s, b, ndigits, bb, table)
+
+		// strip leading zeros
+		// (x != 0; thus s must contain at least one non-zero digit
+		// and the loop will terminate)
+		i = 0
+		for s[i] == '0' {
+			i++
+		}
+	}
+
+	if neg {
+		i--
+		s[i] = '-'
+	}
+
+	return s[i:]
+}
+
+// Convert words of q to base b digits in s. If q is large, it is recursively "split in half"
+// by nat/nat division using tabulated divisors. Otherwise, it is converted iteratively using
+// repeated nat/Word division.
+//
+// The iterative method processes n Words by n divW() calls, each of which visits every Word in the
+// incrementally shortened q for a total of n + (n-1) + (n-2) ... + 2 + 1, or n(n+1)/2 divW()'s.
+// Recursive conversion divides q by its approximate square root, yielding two parts, each half
+// the size of q. Using the iterative method on both halves means 2 * (n/2)(n/2 + 1)/2 divW()'s
+// plus the expensive long div(). Asymptotically, the ratio is favorable at 1/2 the divW()'s, and
+// is made better by splitting the subblocks recursively. Best is to split blocks until one more
+// split would take longer (because of the nat/nat div()) than the twice as many divW()'s of the
+// iterative approach. This threshold is represented by leafSize. Benchmarking of leafSize in the
+// range 2..64 shows that values of 8 and 16 work well, with a 4x speedup at medium lengths and
+// ~30x for 20000 digits. Use nat_test.go's BenchmarkLeafSize tests to optimize leafSize for
+// specific hardware.
+//
+func (q nat) convertWords(s []byte, b Word, ndigits int, bb Word, table []divisor) {
+	// split larger blocks recursively
+	if table != nil {
+		// len(q) > leafSize > 0
+		var r nat
+		index := len(table) - 1
+		for len(q) > leafSize {
+			// find divisor close to sqrt(q) if possible, but in any case < q
+			maxLength := q.bitLen()     // ~= log2 q, or at of least largest possible q of this bit length
+			minLength := maxLength >> 1 // ~= log2 sqrt(q)
+			for index > 0 && table[index-1].nbits > minLength {
+				index-- // desired
+			}
+			if table[index].nbits >= maxLength && table[index].bbb.cmp(q) >= 0 {
+				index--
+				if index < 0 {
+					panic("internal inconsistency")
+				}
+			}
+
+			// split q into the two digit number (q'*bbb + r) to form independent subblocks
+			q, r = q.div(r, q, table[index].bbb)
+
+			// convert subblocks and collect results in s[:h] and s[h:]
+			h := len(s) - table[index].ndigits
+			r.convertWords(s[h:], b, ndigits, bb, table[0:index])
+			s = s[:h] // == q.convertWords(s, b, ndigits, bb, table[0:index+1])
+		}
+	}
+
+	// having split any large blocks now process the remaining (small) block iteratively
+	i := len(s)
+	var r Word
+	if b == 10 {
+		// hard-coding for 10 here speeds this up by 1.25x (allows for / and % by constants)
+		for len(q) > 0 {
+			// extract least significant, base bb "digit"
+			q, r = q.divW(q, bb)
+			for j := 0; j < ndigits && i > 0; j++ {
+				i--
+				// avoid % computation since r%10 == r - int(r/10)*10;
+				// this appears to be faster for BenchmarkString10000Base10
+				// and smaller strings (but a bit slower for larger ones)
+				t := r / 10
+				s[i] = '0' + byte(r-t*10)
+				r = t
+			}
+		}
+	} else {
+		for len(q) > 0 {
+			// extract least significant, base bb "digit"
+			q, r = q.divW(q, bb)
+			for j := 0; j < ndigits && i > 0; j++ {
+				i--
+				s[i] = digits[r%b]
+				r /= b
+			}
+		}
+	}
+
+	// prepend high-order zeros
+	for i > 0 { // while need more leading zeros
+		i--
+		s[i] = '0'
+	}
+}
+
+// Split blocks greater than leafSize Words (or set to 0 to disable recursive conversion)
+// Benchmark and configure leafSize using: go test -bench="Leaf"
+//   8 and 16 effective on 3.0 GHz Xeon "Clovertown" CPU (128 byte cache lines)
+//   8 and 16 effective on 2.66 GHz Core 2 Duo "Penryn" CPU
+var leafSize int = 8 // number of Word-size binary values treat as a monolithic block
+
+type divisor struct {
+	bbb     nat // divisor
+	nbits   int // bit length of divisor (discounting leading zeros) ~= log2(bbb)
+	ndigits int // digit length of divisor in terms of output base digits
+}
+
+var cacheBase10 struct {
+	sync.Mutex
+	table [64]divisor // cached divisors for base 10
+}
+
+// expWW computes x**y
+func (z nat) expWW(x, y Word) nat {
+	return z.expNN(nat(nil).setWord(x), nat(nil).setWord(y), nil)
+}
+
+// construct table of powers of bb*leafSize to use in subdivisions
+func divisors(m int, b Word, ndigits int, bb Word) []divisor {
+	// only compute table when recursive conversion is enabled and x is large
+	if leafSize == 0 || m <= leafSize {
+		return nil
+	}
+
+	// determine k where (bb**leafSize)**(2**k) >= sqrt(x)
+	k := 1
+	for words := leafSize; words < m>>1 && k < len(cacheBase10.table); words <<= 1 {
+		k++
+	}
+
+	// reuse and extend existing table of divisors or create new table as appropriate
+	var table []divisor // for b == 10, table overlaps with cacheBase10.table
+	if b == 10 {
+		cacheBase10.Lock()
+		table = cacheBase10.table[0:k] // reuse old table for this conversion
+	} else {
+		table = make([]divisor, k) // create new table for this conversion
+	}
+
+	// extend table
+	if table[k-1].ndigits == 0 {
+		// add new entries as needed
+		var larger nat
+		for i := 0; i < k; i++ {
+			if table[i].ndigits == 0 {
+				if i == 0 {
+					table[0].bbb = nat(nil).expWW(bb, Word(leafSize))
+					table[0].ndigits = ndigits * leafSize
+				} else {
+					table[i].bbb = nat(nil).sqr(table[i-1].bbb)
+					table[i].ndigits = 2 * table[i-1].ndigits
+				}
+
+				// optimization: exploit aggregated extra bits in macro blocks
+				larger = nat(nil).set(table[i].bbb)
+				for mulAddVWW(larger, larger, b, 0) == 0 {
+					table[i].bbb = table[i].bbb.set(larger)
+					table[i].ndigits++
+				}
+
+				table[i].nbits = table[i].bbb.bitLen()
+			}
+		}
+	}
+
+	if b == 10 {
+		cacheBase10.Unlock()
+	}
+
+	return table
+}
diff --git a/contrib/go/_std_1.18/src/math/big/natdiv.go b/contrib/go/_std_1.18/src/math/big/natdiv.go
new file mode 100644
index 0000000000..882bb6d3ba
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/natdiv.go
@@ -0,0 +1,884 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+
+Multi-precision division. Here be dragons.
+
+Given u and v, where u is n+m digits, and v is n digits (with no leading zeros),
+the goal is to return quo, rem such that u = quo*v + rem, where 0 ≤ rem < v.
+That is, quo = ⌊u/v⌋ where ⌊x⌋ denotes the floor (truncation to integer) of x,
+and rem = u - quo·v.
+
+
+Long Division
+
+Division in a computer proceeds the same as long division in elementary school,
+but computers are not as good as schoolchildren at following vague directions,
+so we have to be much more precise about the actual steps and what can happen.
+
+We work from most to least significant digit of the quotient, doing:
+
+ • Guess a digit q, the number of v to subtract from the current
+   section of u to zero out the topmost digit.
+ • Check the guess by multiplying q·v and comparing it against
+   the current section of u, adjusting the guess as needed.
+ • Subtract q·v from the current section of u.
+ • Add q to the corresponding section of the result quo.
+
+When all digits have been processed, the final remainder is left in u
+and returned as rem.
+
+For example, here is a sketch of dividing 5 digits by 3 digits (n=3, m=2).
+
+	                 q₂ q₁ q₀
+	         _________________
+	v₂ v₁ v₀ ) u₄ u₃ u₂ u₁ u₀
+	           ↓  ↓  ↓  |  |
+	          [u₄ u₃ u₂]|  |
+	        - [  q₂·v  ]|  |
+	        ----------- ↓  |
+	          [  rem  | u₁]|
+	        - [    q₁·v   ]|
+	           ----------- ↓
+	             [  rem  | u₀]
+	           - [    q₀·v   ]
+	              ------------
+	                [  rem   ]
+
+Instead of creating new storage for the remainders and copying digits from u
+as indicated by the arrows, we use u's storage directly as both the source
+and destination of the subtractions, so that the remainders overwrite
+successive overlapping sections of u as the division proceeds, using a slice
+of u to identify the current section. This avoids all the copying as well as
+shifting of remainders.
+
+Division of u with n+m digits by v with n digits (in base B) can in general
+produce at most m+1 digits, because:
+
+  • u < B^(n+m)               [B^(n+m) has n+m+1 digits]
+  • v ≥ B^(n-1)               [B^(n-1) is the smallest n-digit number]
+  • u/v < B^(n+m) / B^(n-1)   [divide bounds for u, v]
+  • u/v < B^(m+1)             [simplify]
+
+The first step is special: it takes the top n digits of u and divides them by
+the n digits of v, producing the first quotient digit and an n-digit remainder.
+In the example, q₂ = ⌊u₄u₃u₂ / v⌋.
+
+The first step divides n digits by n digits to ensure that it produces only a
+single digit.
+
+Each subsequent step appends the next digit from u to the remainder and divides
+those n+1 digits by the n digits of v, producing another quotient digit and a
+new n-digit remainder.
+
+Subsequent steps divide n+1 digits by n digits, an operation that in general
+might produce two digits. However, as used in the algorithm, that division is
+guaranteed to produce only a single digit. The dividend is of the form
+rem·B + d, where rem is a remainder from the previous step and d is a single
+digit, so:
+
+ • rem ≤ v - 1                 [rem is a remainder from dividing by v]
+ • rem·B ≤ v·B - B             [multiply by B]
+ • d ≤ B - 1                   [d is a single digit]
+ • rem·B + d ≤ v·B - 1         [add]
+ • rem·B + d < v·B             [change ≤ to <]
+ • (rem·B + d)/v < B           [divide by v]
+
+
+Guess and Check
+
+At each step we need to divide n+1 digits by n digits, but this is for the
+implementation of division by n digits, so we can't just invoke a division
+routine: we _are_ the division routine. Instead, we guess at the answer and
+then check it using multiplication. If the guess is wrong, we correct it.
+
+How can this guessing possibly be efficient? It turns out that the following
+statement (let's call it the Good Guess Guarantee) is true.
+
+If
+
+ • q = ⌊u/v⌋ where u is n+1 digits and v is n digits,
+ • q < B, and
+ • the topmost digit of v = vₙ₋₁ ≥ B/2,
+
+then q̂ = ⌊uₙuₙ₋₁ / vₙ₋₁⌋ satisfies q ≤ q̂ ≤ q+2. (Proof below.)
+
+That is, if we know the answer has only a single digit and we guess an answer
+by ignoring the bottom n-1 digits of u and v, using a 2-by-1-digit division,
+then that guess is at least as large as the correct answer. It is also not
+too much larger: it is off by at most two from the correct answer.
+
+Note that in the first step of the overall division, which is an n-by-n-digit
+division, the 2-by-1 guess uses an implicit uₙ = 0.
+
+Note that using a 2-by-1-digit division here does not mean calling ourselves
+recursively. Instead, we use an efficient direct hardware implementation of
+that operation.
+
+Note that because q is u/v rounded down, q·v must not exceed u: u ≥ q·v.
+If a guess q̂ is too big, it will not satisfy this test. Viewed a different way,
+the remainder r̂ for a given q̂ is u - q̂·v, which must be positive. If it is
+negative, then the guess q̂ is too big.
+
+This gives us a way to compute q. First compute q̂ with 2-by-1-digit division.
+Then, while u < q̂·v, decrement q̂; this loop executes at most twice, because
+q̂ ≤ q+2.
+
+
+Scaling Inputs
+
+The Good Guess Guarantee requires that the top digit of v (vₙ₋₁) be at least B/2.
+For example in base 10, ⌊172/19⌋ = 9, but ⌊18/1⌋ = 18: the guess is wildly off
+because the first digit 1 is smaller than B/2 = 5.
+
+We can ensure that v has a large top digit by multiplying both u and v by the
+right amount. Continuing the example, if we multiply both 172 and 19 by 3, we
+now have ⌊516/57⌋, the leading digit of v is now ≥ 5, and sure enough
+⌊51/5⌋ = 10 is much closer to the correct answer 9. It would be easier here
+to multiply by 4, because that can be done with a shift. Specifically, we can
+always count the number of leading zeros i in the first digit of v and then
+shift both u and v left by i bits.
+
+Having scaled u and v, the value ⌊u/v⌋ is unchanged, but the remainder will
+be scaled: 172 mod 19 is 1, but 516 mod 57 is 3. We have to divide the remainder
+by the scaling factor (shifting right i bits) when we finish.
+
+Note that these shifts happen before and after the entire division algorithm,
+not at each step in the per-digit iteration.
+
+Note the effect of scaling inputs on the size of the possible quotient.
+In the scaled u/v, u can gain a digit from scaling; v never does, because we
+pick the scaling factor to make v's top digit larger but without overflowing.
+If u and v have n+m and n digits after scaling, then:
+
+  • u < B^(n+m)               [B^(n+m) has n+m+1 digits]
+  • v ≥ B^n / 2               [vₙ₋₁ ≥ B/2, so vₙ₋₁·B^(n-1) ≥ B^n/2]
+  • u/v < B^(n+m) / (B^n / 2) [divide bounds for u, v]
+  • u/v < 2 B^m               [simplify]
+
+The quotient can still have m+1 significant digits, but if so the top digit
+must be a 1. This provides a different way to handle the first digit of the
+result: compare the top n digits of u against v and fill in either a 0 or a 1.
+
+
+Refining Guesses
+
+Before we check whether u < q̂·v, we can adjust our guess to change it from
+q̂ = ⌊uₙuₙ₋₁ / vₙ₋₁⌋ into the refined guess ⌊uₙuₙ₋₁uₙ₋₂ / vₙ₋₁vₙ₋₂⌋.
+Although not mentioned above, the Good Guess Guarantee also promises that this
+3-by-2-digit division guess is more precise and at most one away from the real
+answer q. The improvement from the 2-by-1 to the 3-by-2 guess can also be done
+without n-digit math.
+
+If we have a guess q̂ = ⌊uₙuₙ₋₁ / vₙ₋₁⌋ and we want to see if it also equal to
+⌊uₙuₙ₋₁uₙ₋₂ / vₙ₋₁vₙ₋₂⌋, we can use the same check we would for the full division:
+if uₙuₙ₋₁uₙ₋₂ < q̂·vₙ₋₁vₙ₋₂, then the guess is too large and should be reduced.
+
+Checking uₙuₙ₋₁uₙ₋₂ < q̂·vₙ₋₁vₙ₋₂ is the same as uₙuₙ₋₁uₙ₋₂ - q̂·vₙ₋₁vₙ₋₂ < 0,
+and
+
+	uₙuₙ₋₁uₙ₋₂ - q̂·vₙ₋₁vₙ₋₂ = (uₙuₙ₋₁·B + uₙ₋₂) - q̂·(vₙ₋₁·B + vₙ₋₂)
+	                          [splitting off the bottom digit]
+	                      = (uₙuₙ₋₁ - q̂·vₙ₋₁)·B + uₙ₋₂ - q̂·vₙ₋₂
+	                          [regrouping]
+
+The expression (uₙuₙ₋₁ - q̂·vₙ₋₁) is the remainder of uₙuₙ₋₁ / vₙ₋₁.
+If the initial guess returns both q̂ and its remainder r̂, then checking
+whether uₙuₙ₋₁uₙ₋₂ < q̂·vₙ₋₁vₙ₋₂ is the same as checking r̂·B + uₙ₋₂ < q̂·vₙ₋₂.
+
+If we find that r̂·B + uₙ₋₂ < q̂·vₙ₋₂, then we can adjust the guess by
+decrementing q̂ and adding vₙ₋₁ to r̂. We repeat until r̂·B + uₙ₋₂ ≥ q̂·vₙ₋₂.
+(As before, this fixup is only needed at most twice.)
+
+Now that q̂ = ⌊uₙuₙ₋₁uₙ₋₂ / vₙ₋₁vₙ₋₂⌋, as mentioned above it is at most one
+away from the correct q, and we've avoided doing any n-digit math.
+(If we need the new remainder, it can be computed as r̂·B + uₙ₋₂ - q̂·vₙ₋₂.)
+
+The final check u < q̂·v and the possible fixup must be done at full precision.
+For random inputs, a fixup at this step is exceedingly rare: the 3-by-2 guess
+is not often wrong at all. But still we must do the check. Note that since the
+3-by-2 guess is off by at most 1, it can be convenient to perform the final
+u < q̂·v as part of the computation of the remainder r = u - q̂·v. If the
+subtraction underflows, decremeting q̂ and adding one v back to r is enough to
+arrive at the final q, r.
+
+That's the entirety of long division: scale the inputs, and then loop over
+each output position, guessing, checking, and correcting the next output digit.
+
+For a 2n-digit number divided by an n-digit number (the worst size-n case for
+division complexity), this algorithm uses n+1 iterations, each of which must do
+at least the 1-by-n-digit multiplication q̂·v. That's O(n) iterations of
+O(n) time each, so O(n²) time overall.
+
+
+Recursive Division
+
+For very large inputs, it is possible to improve on the O(n²) algorithm.
+Let's call a group of n/2 real digits a (very) “wide digit”. We can run the
+standard long division algorithm explained above over the wide digits instead of
+the actual digits. This will result in many fewer steps, but the math involved in
+each step is more work.
+
+Where basic long division uses a 2-by-1-digit division to guess the initial q̂,
+the new algorithm must use a 2-by-1-wide-digit division, which is of course
+really an n-by-n/2-digit division. That's OK: if we implement n-digit division
+in terms of n/2-digit division, the recursion will terminate when the divisor
+becomes small enough to handle with standard long division or even with the
+2-by-1 hardware instruction.
+
+For example, here is a sketch of dividing 10 digits by 4, proceeding with
+wide digits corresponding to two regular digits. The first step, still special,
+must leave off a (regular) digit, dividing 5 by 4 and producing a 4-digit
+remainder less than v. The middle steps divide 6 digits by 4, guaranteed to
+produce two output digits each (one wide digit) with 4-digit remainders.
+The final step must use what it has: the 4-digit remainder plus one more,
+5 digits to divide by 4.
+
+	                       q₆ q₅ q₄ q₃ q₂ q₁ q₀
+	            _______________________________
+	v₃ v₂ v₁ v₀ ) u₉ u₈ u₇ u₆ u₅ u₄ u₃ u₂ u₁ u₀
+	              ↓  ↓  ↓  ↓  ↓  |  |  |  |  |
+	             [u₉ u₈ u₇ u₆ u₅]|  |  |  |  |
+	           - [    q₆q₅·v    ]|  |  |  |  |
+	           ----------------- ↓  ↓  |  |  |
+	                [    rem    |u₄ u₃]|  |  |
+	              - [     q₄q₃·v      ]|  |  |
+	              -------------------- ↓  ↓  |
+	                      [    rem    |u₂ u₁]|
+	                    - [     q₂q₁·v      ]|
+	                    -------------------- ↓
+	                            [    rem    |u₀]
+	                          - [     q₀·v     ]
+	                          ------------------
+	                               [    rem    ]
+
+An alternative would be to look ahead to how well n/2 divides into n+m and
+adjust the first step to use fewer digits as needed, making the first step
+more special to make the last step not special at all. For example, using the
+same input, we could choose to use only 4 digits in the first step, leaving
+a full wide digit for the last step:
+
+	                       q₆ q₅ q₄ q₃ q₂ q₁ q₀
+	            _______________________________
+	v₃ v₂ v₁ v₀ ) u₉ u₈ u₇ u₆ u₅ u₄ u₃ u₂ u₁ u₀
+	              ↓  ↓  ↓  ↓  |  |  |  |  |  |
+	             [u₉ u₈ u₇ u₆]|  |  |  |  |  |
+	           - [    q₆·v   ]|  |  |  |  |  |
+	           -------------- ↓  ↓  |  |  |  |
+	             [    rem    |u₅ u₄]|  |  |  |
+	           - [     q₅q₄·v      ]|  |  |  |
+	           -------------------- ↓  ↓  |  |
+	                   [    rem    |u₃ u₂]|  |
+	                 - [     q₃q₂·v      ]|  |
+	                 -------------------- ↓  ↓
+	                         [    rem    |u₁ u₀]
+	                       - [     q₁q₀·v      ]
+	                       ---------------------
+	                               [    rem    ]
+
+Today, the code in divRecursiveStep works like the first example. Perhaps in
+the future we will make it work like the alternative, to avoid a special case
+in the final iteration.
+
+Either way, each step is a 3-by-2-wide-digit division approximated first by
+a 2-by-1-wide-digit division, just as we did for regular digits in long division.
+Because the actual answer we want is a 3-by-2-wide-digit division, instead of
+multiplying q̂·v directly during the fixup, we can use the quick refinement
+from long division (an n/2-by-n/2 multiply) to correct q to its actual value
+and also compute the remainder (as mentioned above), and then stop after that,
+never doing a full n-by-n multiply.
+
+Instead of using an n-by-n/2-digit division to produce n/2 digits, we can add
+(not discard) one more real digit, doing an (n+1)-by-(n/2+1)-digit division that
+produces n/2+1 digits. That single extra digit tightens the Good Guess Guarantee
+to q ≤ q̂ ≤ q+1 and lets us drop long division's special treatment of the first
+digit. These benefits are discussed more after the Good Guess Guarantee proof
+below.
+
+
+How Fast is Recursive Division?
+
+For a 2n-by-n-digit division, this algorithm runs a 4-by-2 long division over
+wide digits, producing two wide digits plus a possible leading regular digit 1,
+which can be handled without a recursive call. That is, the algorithm uses two
+full iterations, each using an n-by-n/2-digit division and an n/2-by-n/2-digit
+multiplication, along with a few n-digit additions and subtractions. The standard
+n-by-n-digit multiplication algorithm requires O(n²) time, making the overall
+algorithm require time T(n) where
+
+	T(n) = 2T(n/2) + O(n) + O(n²)
+
+which, by the Bentley-Haken-Saxe theorem, ends up reducing to T(n) = O(n²).
+This is not an improvement over regular long division.
+
+When the number of digits n becomes large enough, Karatsuba's algorithm for
+multiplication can be used instead, which takes O(n^log₂3) = O(n^1.6) time.
+(Karatsuba multiplication is implemented in func karatsuba in nat.go.)
+That makes the overall recursive division algorithm take O(n^1.6) time as well,
+which is an improvement, but again only for large enough numbers.
+
+It is not critical to make sure that every recursion does only two recursive
+calls. While in general the number of recursive calls can change the time
+analysis, in this case doing three calls does not change the analysis:
+
+	T(n) = 3T(n/2) + O(n) + O(n^log₂3)
+
+ends up being T(n) = O(n^log₂3). Because the Karatsuba multiplication taking
+time O(n^log₂3) is itself doing 3 half-sized recursions, doing three for the
+division does not hurt the asymptotic performance. Of course, it is likely
+still faster in practice to do two.
+
+
+Proof of the Good Guess Guarantee
+
+Given numbers x, y, let us break them into the quotients and remainders when
+divided by some scaling factor S, with the added constraints that the quotient
+x/y and the high part of y are both less than some limit T, and that the high
+part of y is at least half as big as T.
+
+	x₁ = ⌊x/S⌋        y₁ = ⌊y/S⌋
+	x₀ = x mod S      y₀ = y mod S
+
+	x  = x₁·S + x₀    0 ≤ x₀ < S    x/y < T
+	y  = y₁·S + y₀    0 ≤ y₀ < S    T/2 ≤ y₁ < T
+
+And consider the two truncated quotients:
+
+	q = ⌊x/y⌋
+	q̂ = ⌊x₁/y₁⌋
+
+We will prove that q ≤ q̂ ≤ q+2.
+
+The guarantee makes no real demands on the scaling factor S: it is simply the
+magnitude of the digits cut from both x and y to produce x₁ and y₁.
+The guarantee makes only limited demands on T: it must be large enough to hold
+the quotient x/y, and y₁ must have roughly the same size.
+
+To apply to the earlier discussion of 2-by-1 guesses in long division,
+we would choose:
+
+	S  = Bⁿ⁻¹
+	T  = B
+	x  = u
+	x₁ = uₙuₙ₋₁
+	x₀ = uₙ₋₂...u₀
+	y  = v
+	y₁ = vₙ₋₁
+	y₀ = vₙ₋₂...u₀
+
+These simpler variables avoid repeating those longer expressions in the proof.
+
+Note also that, by definition, truncating division ⌊x/y⌋ satisfies
+
+	x/y - 1 < ⌊x/y⌋ ≤ x/y.
+
+This fact will be used a few times in the proofs.
+
+Proof that q ≤ q̂:
+
+	q̂·y₁ = ⌊x₁/y₁⌋·y₁                      [by definition, q̂ = ⌊x₁/y₁⌋]
+	     > (x₁/y₁ - 1)·y₁                  [x₁/y₁ - 1 < ⌊x₁/y₁⌋]
+	     = x₁ - y₁                         [distribute y₁]
+
+	So q̂·y₁ > x₁ - y₁.
+	Since q̂·y₁ is an integer, q̂·y₁ ≥ x₁ - y₁ + 1.
+
+	q̂ - q = q̂ - ⌊x/y⌋                      [by definition, q = ⌊x/y⌋]
+	      ≥ q̂ - x/y                        [⌊x/y⌋ < x/y]
+	      = (1/y)·(q̂·y - x)                [factor out 1/y]
+	      ≥ (1/y)·(q̂·y₁·S - x)             [y = y₁·S + y₀ ≥ y₁·S]
+	      ≥ (1/y)·((x₁ - y₁ + 1)·S - x)    [above: q̂·y₁ ≥ x₁ - y₁ + 1]
+	      = (1/y)·(x₁·S - y₁·S + S - x)    [distribute S]
+	      = (1/y)·(S - x₀ - y₁·S)          [-x = -x₁·S - x₀]
+	      > -y₁·S / y                      [x₀ < S, so S - x₀ < 0; drop it]
+	      ≥ -1                             [y₁·S ≤ y]
+
+	So q̂ - q > -1.
+	Since q̂ - q is an integer, q̂ - q ≥ 0, or equivalently q ≤ q̂.
+
+Proof that q̂ ≤ q+2:
+
+	x₁/y₁ - x/y = x₁·S/y₁·S - x/y          [multiply left term by S/S]
+	            ≤ x/y₁·S - x/y             [x₁S ≤ x]
+	            = (x/y)·(y/y₁·S - 1)       [factor out x/y]
+	            = (x/y)·((y - y₁·S)/y₁·S)  [move -1 into y/y₁·S fraction]
+	            = (x/y)·(y₀/y₁·S)          [y - y₁·S = y₀]
+	            = (x/y)·(1/y₁)·(y₀/S)      [factor out 1/y₁]
+	            < (x/y)·(1/y₁)             [y₀ < S, so y₀/S < 1]
+	            ≤ (x/y)·(2/T)              [y₁ ≥ T/2, so 1/y₁ ≤ 2/T]
+	            < T·(2/T)                  [x/y < T]
+	            = 2                        [T·(2/T) = 2]
+
+	So x₁/y₁ - x/y < 2.
+
+	q̂ - q = ⌊x₁/y₁⌋ - q                    [by definition, q̂ = ⌊x₁/y₁⌋]
+	      = ⌊x₁/y₁⌋ - ⌊x/y⌋                [by definition, q = ⌊x/y⌋]
+	      ≤ x₁/y₁ - ⌊x/y⌋                  [⌊x₁/y₁⌋ ≤ x₁/y₁]
+	      < x₁/y₁ - (x/y - 1)              [⌊x/y⌋ > x/y - 1]
+	      = (x₁/y₁ - x/y) + 1              [regrouping]
+	      < 2 + 1                          [above: x₁/y₁ - x/y < 2]
+	      = 3
+
+	So q̂ - q < 3.
+	Since q̂ - q is an integer, q̂ - q ≤ 2.
+
+Note that when x/y < T/2, the bounds tighten to x₁/y₁ - x/y < 1 and therefore
+q̂ - q ≤ 1.
+
+Note also that in the general case 2n-by-n division where we don't know that
+x/y < T, we do know that x/y < 2T, yielding the bound q̂ - q ≤ 4. So we could
+remove the special case first step of long division as long as we allow the
+first fixup loop to run up to four times. (Using a simple comparison to decide
+whether the first digit is 0 or 1 is still more efficient, though.)
+
+Finally, note that when dividing three leading base-B digits by two (scaled),
+we have T = B² and x/y < B = T/B, a much tighter bound than x/y < T.
+This in turn yields the much tighter bound x₁/y₁ - x/y < 2/B. This means that
+⌊x₁/y₁⌋ and ⌊x/y⌋ can only differ when x/y is less than 2/B greater than an
+integer. For random x and y, the chance of this is 2/B, or, for large B,
+approximately zero. This means that after we produce the 3-by-2 guess in the
+long division algorithm, the fixup loop essentially never runs.
+
+In the recursive algorithm, the extra digit in (2·⌊n/2⌋+1)-by-(⌊n/2⌋+1)-digit
+division has exactly the same effect: the probability of needing a fixup is the
+same 2/B. Even better, we can allow the general case x/y < 2T and the fixup
+probability only grows to 4/B, still essentially zero.
+
+
+References
+
+There are no great references for implementing long division; thus this comment.
+Here are some notes about what to expect from the obvious references.
+
+Knuth Volume 2 (Seminumerical Algorithms) section 4.3.1 is the usual canonical
+reference for long division, but that entire series is highly compressed, never
+repeating a necessary fact and leaving important insights to the exercises.
+For example, no rationale whatsoever is given for the calculation that extends
+q̂ from a 2-by-1 to a 3-by-2 guess, nor why it reduces the error bound.
+The proof that the calculation even has the desired effect is left to exercises.
+The solutions to those exercises provided at the back of the book are entirely
+calculations, still with no explanation as to what is going on or how you would
+arrive at the idea of doing those exact calculations. Nowhere is it mentioned
+that this test extends the 2-by-1 guess into a 3-by-2 guess. The proof of the
+Good Guess Guarantee is only for the 2-by-1 guess and argues by contradiction,
+making it difficult to understand how modifications like adding another digit
+or adjusting the quotient range affects the overall bound.
+
+All that said, Knuth remains the canonical reference. It is dense but packed
+full of information and references, and the proofs are simpler than many other
+presentations. The proofs above are reworkings of Knuth's to remove the
+arguments by contradiction and add explanations or steps that Knuth omitted.
+But beware of errors in older printings. Take the published errata with you.
+
+Brinch Hansen's “Multiple-length Division Revisited: a Tour of the Minefield”
+starts with a blunt critique of Knuth's presentation (among others) and then
+presents a more detailed and easier to follow treatment of long division,
+including an implementation in Pascal. But the algorithm and implementation
+work entirely in terms of 3-by-2 division, which is much less useful on modern
+hardware than an algorithm using 2-by-1 division. The proofs are a bit too
+focused on digit counting and seem needlessly complex, especially compared to
+the ones given above.
+
+Burnikel and Ziegler's “Fast Recursive Division” introduced the key insight of
+implementing division by an n-digit divisor using recursive calls to division
+by an n/2-digit divisor, relying on Karatsuba multiplication to yield a
+sub-quadratic run time. However, the presentation decisions are made almost
+entirely for the purpose of simplifying the run-time analysis, rather than
+simplifying the presentation. Instead of a single algorithm that loops over
+quotient digits, the paper presents two mutually-recursive algorithms, for
+2n-by-n and 3n-by-2n. The paper also does not present any general (n+m)-by-n
+algorithm.
+
+The proofs in the paper are remarkably complex, especially considering that
+the algorithm is at its core just long division on wide digits, so that the
+usual long division proofs apply essentially unaltered.
+*/
+
+package big
+
+import "math/bits"
+
+// div returns q, r such that q = ⌊u/v⌋ and r = u%v = u - q·v.
+// It uses z and z2 as the storage for q and r.
+func (z nat) div(z2, u, v nat) (q, r nat) {
+	if len(v) == 0 {
+		panic("division by zero")
+	}
+
+	if u.cmp(v) < 0 {
+		q = z[:0]
+		r = z2.set(u)
+		return
+	}
+
+	if len(v) == 1 {
+		// Short division: long optimized for a single-word divisor.
+		// In that case, the 2-by-1 guess is all we need at each step.
+		var r2 Word
+		q, r2 = z.divW(u, v[0])
+		r = z2.setWord(r2)
+		return
+	}
+
+	q, r = z.divLarge(z2, u, v)
+	return
+}
+
+// divW returns q, r such that q = ⌊x/y⌋ and r = x%y = x - q·y.
+// It uses z as the storage for q.
+// Note that y is a single digit (Word), not a big number.
+func (z nat) divW(x nat, y Word) (q nat, r Word) {
+	m := len(x)
+	switch {
+	case y == 0:
+		panic("division by zero")
+	case y == 1:
+		q = z.set(x) // result is x
+		return
+	case m == 0:
+		q = z[:0] // result is 0
+		return
+	}
+	// m > 0
+	z = z.make(m)
+	r = divWVW(z, 0, x, y)
+	q = z.norm()
+	return
+}
+
+// modW returns x % d.
+func (x nat) modW(d Word) (r Word) {
+	// TODO(agl): we don't actually need to store the q value.
+	var q nat
+	q = q.make(len(x))
+	return divWVW(q, 0, x, d)
+}
+
+// divWVW overwrites z with ⌊x/y⌋, returning the remainder r.
+// The caller must ensure that len(z) = len(x).
+func divWVW(z []Word, xn Word, x []Word, y Word) (r Word) {
+	r = xn
+	if len(x) == 1 {
+		qq, rr := bits.Div(uint(r), uint(x[0]), uint(y))
+		z[0] = Word(qq)
+		return Word(rr)
+	}
+	rec := reciprocalWord(y)
+	for i := len(z) - 1; i >= 0; i-- {
+		z[i], r = divWW(r, x[i], y, rec)
+	}
+	return r
+}
+
+// div returns q, r such that q = ⌊uIn/vIn⌋ and r = uIn%vIn = uIn - q·vIn.
+// It uses z and u as the storage for q and r.
+// The caller must ensure that len(vIn) ≥ 2 (use divW otherwise)
+// and that len(uIn) ≥ len(vIn) (the answer is 0, uIn otherwise).
+func (z nat) divLarge(u, uIn, vIn nat) (q, r nat) {
+	n := len(vIn)
+	m := len(uIn) - n
+
+	// Scale the inputs so vIn's top bit is 1 (see “Scaling Inputs” above).
+	// vIn is treated as a read-only input (it may be in use by another
+	// goroutine), so we must make a copy.
+	// uIn is copied to u.
+	shift := nlz(vIn[n-1])
+	vp := getNat(n)
+	v := *vp
+	shlVU(v, vIn, shift)
+	u = u.make(len(uIn) + 1)
+	u[len(uIn)] = shlVU(u[0:len(uIn)], uIn, shift)
+
+	// The caller should not pass aliased z and u, since those are
+	// the two different outputs, but correct just in case.
+	if alias(z, u) {
+		z = nil
+	}
+	q = z.make(m + 1)
+
+	// Use basic or recursive long division depending on size.
+	if n < divRecursiveThreshold {
+		q.divBasic(u, v)
+	} else {
+		q.divRecursive(u, v)
+	}
+	putNat(vp)
+
+	q = q.norm()
+
+	// Undo scaling of remainder.
+	shrVU(u, u, shift)
+	r = u.norm()
+
+	return q, r
+}
+
+// divBasic implements long division as described above.
+// It overwrites q with ⌊u/v⌋ and overwrites u with the remainder r.
+// q must be large enough to hold ⌊u/v⌋.
+func (q nat) divBasic(u, v nat) {
+	n := len(v)
+	m := len(u) - n
+
+	qhatvp := getNat(n + 1)
+	qhatv := *qhatvp
+
+	// Set up for divWW below, precomputing reciprocal argument.
+	vn1 := v[n-1]
+	rec := reciprocalWord(vn1)
+
+	// Compute each digit of quotient.
+	for j := m; j >= 0; j-- {
+		// Compute the 2-by-1 guess q̂.
+		// The first iteration must invent a leading 0 for u.
+		qhat := Word(_M)
+		var ujn Word
+		if j+n < len(u) {
+			ujn = u[j+n]
+		}
+
+		// ujn ≤ vn1, or else q̂ would be more than one digit.
+		// For ujn == vn1, we set q̂ to the max digit M above.
+		// Otherwise, we compute the 2-by-1 guess.
+		if ujn != vn1 {
+			var rhat Word
+			qhat, rhat = divWW(ujn, u[j+n-1], vn1, rec)
+
+			// Refine q̂ to a 3-by-2 guess. See “Refining Guesses” above.
+			vn2 := v[n-2]
+			x1, x2 := mulWW(qhat, vn2)
+			ujn2 := u[j+n-2]
+			for greaterThan(x1, x2, rhat, ujn2) { // x1x2 > r̂ u[j+n-2]
+				qhat--
+				prevRhat := rhat
+				rhat += vn1
+				// If r̂  overflows, then
+				// r̂ u[j+n-2]v[n-1] is now definitely > x1 x2.
+				if rhat < prevRhat {
+					break
+				}
+				// TODO(rsc): No need for a full mulWW.
+				// x2 += vn2; if x2 overflows, x1++
+				x1, x2 = mulWW(qhat, vn2)
+			}
+		}
+
+		// Compute q̂·v.
+		qhatv[n] = mulAddVWW(qhatv[0:n], v, qhat, 0)
+		qhl := len(qhatv)
+		if j+qhl > len(u) && qhatv[n] == 0 {
+			qhl--
+		}
+
+		// Subtract q̂·v from the current section of u.
+		// If it underflows, q̂·v > u, which we fix up
+		// by decrementing q̂ and adding v back.
+		c := subVV(u[j:j+qhl], u[j:], qhatv)
+		if c != 0 {
+			c := addVV(u[j:j+n], u[j:], v)
+			// If n == qhl, the carry from subVV and the carry from addVV
+			// cancel out and don't affect u[j+n].
+			if n < qhl {
+				u[j+n] += c
+			}
+			qhat--
+		}
+
+		// Save quotient digit.
+		// Caller may know the top digit is zero and not leave room for it.
+		if j == m && m == len(q) && qhat == 0 {
+			continue
+		}
+		q[j] = qhat
+	}
+
+	putNat(qhatvp)
+}
+
+// greaterThan reports whether the two digit numbers x1 x2 > y1 y2.
+// TODO(rsc): In contradiction to most of this file, x1 is the high
+// digit and x2 is the low digit. This should be fixed.
+func greaterThan(x1, x2, y1, y2 Word) bool {
+	return x1 > y1 || x1 == y1 && x2 > y2
+}
+
+// divRecursiveThreshold is the number of divisor digits
+// at which point divRecursive is faster than divBasic.
+const divRecursiveThreshold = 100
+
+// divRecursive implements recursive division as described above.
+// It overwrites z with ⌊u/v⌋ and overwrites u with the remainder r.
+// z must be large enough to hold ⌊u/v⌋.
+// This function is just for allocating and freeing temporaries
+// around divRecursiveStep, the real implementation.
+func (z nat) divRecursive(u, v nat) {
+	// Recursion depth is (much) less than 2 log₂(len(v)).
+	// Allocate a slice of temporaries to be reused across recursion,
+	// plus one extra temporary not live across the recursion.
+	recDepth := 2 * bits.Len(uint(len(v)))
+	tmp := getNat(3 * len(v))
+	temps := make([]*nat, recDepth)
+
+	z.clear()
+	z.divRecursiveStep(u, v, 0, tmp, temps)
+
+	// Free temporaries.
+	for _, n := range temps {
+		if n != nil {
+			putNat(n)
+		}
+	}
+	putNat(tmp)
+}
+
+// divRecursiveStep is the actual implementation of recursive division.
+// It adds ⌊u/v⌋ to z and overwrites u with the remainder r.
+// z must be large enough to hold ⌊u/v⌋.
+// It uses temps[depth] (allocating if needed) as a temporary live across
+// the recursive call. It also uses tmp, but not live across the recursion.
+func (z nat) divRecursiveStep(u, v nat, depth int, tmp *nat, temps []*nat) {
+	// u is a subsection of the original and may have leading zeros.
+	// TODO(rsc): The v = v.norm() is useless and should be removed.
+	// We know (and require) that v's top digit is ≥ B/2.
+	u = u.norm()
+	v = v.norm()
+	if len(u) == 0 {
+		z.clear()
+		return
+	}
+
+	// Fall back to basic division if the problem is now small enough.
+	n := len(v)
+	if n < divRecursiveThreshold {
+		z.divBasic(u, v)
+		return
+	}
+
+	// Nothing to do if u is shorter than v (implies u < v).
+	m := len(u) - n
+	if m < 0 {
+		return
+	}
+
+	// We consider B digits in a row as a single wide digit.
+	// (See “Recursive Division” above.)
+	//
+	// TODO(rsc): rename B to Wide, to avoid confusion with _B,
+	// which is something entirely different.
+	// TODO(rsc): Look into whether using ⌈n/2⌉ is better than ⌊n/2⌋.
+	B := n / 2
+
+	// Allocate a nat for qhat below.
+	if temps[depth] == nil {
+		temps[depth] = getNat(n) // TODO(rsc): Can be just B+1.
+	} else {
+		*temps[depth] = temps[depth].make(B + 1)
+	}
+
+	// Compute each wide digit of the quotient.
+	//
+	// TODO(rsc): Change the loop to be
+	//	for j := (m+B-1)/B*B; j > 0; j -= B {
+	// which will make the final step a regular step, letting us
+	// delete what amounts to an extra copy of the loop body below.
+	j := m
+	for j > B {
+		// Divide u[j-B:j+n] (3 wide digits) by v (2 wide digits).
+		// First make the 2-by-1-wide-digit guess using a recursive call.
+		// Then extend the guess to the full 3-by-2 (see “Refining Guesses”).
+		//
+		// For the 2-by-1-wide-digit guess, instead of doing 2B-by-B-digit,
+		// we use a (2B+1)-by-(B+1) digit, which handles the possibility that
+		// the result has an extra leading 1 digit as well as guaranteeing
+		// that the computed q̂ will be off by at most 1 instead of 2.
+
+		// s is the number of digits to drop from the 3B- and 2B-digit chunks.
+		// We drop B-1 to be left with 2B+1 and B+1.
+		s := (B - 1)
+
+		// uu is the up-to-3B-digit section of u we are working on.
+		uu := u[j-B:]
+
+		// Compute the 2-by-1 guess q̂, leaving r̂ in uu[s:B+n].
+		qhat := *temps[depth]
+		qhat.clear()
+		qhat.divRecursiveStep(uu[s:B+n], v[s:], depth+1, tmp, temps)
+		qhat = qhat.norm()
+
+		// Extend to a 3-by-2 quotient and remainder.
+		// Because divRecursiveStep overwrote the top part of uu with
+		// the remainder r̂, the full uu already contains the equivalent
+		// of r̂·B + uₙ₋₂ from the “Refining Guesses” discussion.
+		// Subtracting q̂·vₙ₋₂ from it will compute the full-length remainder.
+		// If that subtraction underflows, q̂·v > u, which we fix up
+		// by decrementing q̂ and adding v back, same as in long division.
+
+		// TODO(rsc): Instead of subtract and fix-up, this code is computing
+		// q̂·vₙ₋₂ and decrementing q̂ until that product is ≤ u.
+		// But we can do the subtraction directly, as in the comment above
+		// and in long division, because we know that q̂ is wrong by at most one.
+		qhatv := tmp.make(3 * n)
+		qhatv.clear()
+		qhatv = qhatv.mul(qhat, v[:s])
+		for i := 0; i < 2; i++ {
+			e := qhatv.cmp(uu.norm())
+			if e <= 0 {
+				break
+			}
+			subVW(qhat, qhat, 1)
+			c := subVV(qhatv[:s], qhatv[:s], v[:s])
+			if len(qhatv) > s {
+				subVW(qhatv[s:], qhatv[s:], c)
+			}
+			addAt(uu[s:], v[s:], 0)
+		}
+		if qhatv.cmp(uu.norm()) > 0 {
+			panic("impossible")
+		}
+		c := subVV(uu[:len(qhatv)], uu[:len(qhatv)], qhatv)
+		if c > 0 {
+			subVW(uu[len(qhatv):], uu[len(qhatv):], c)
+		}
+		addAt(z, qhat, j-B)
+		j -= B
+	}
+
+	// TODO(rsc): Rewrite loop as described above and delete all this code.
+
+	// Now u < (v<<B), compute lower bits in the same way.
+	// Choose shift = B-1 again.
+	s := B - 1
+	qhat := *temps[depth]
+	qhat.clear()
+	qhat.divRecursiveStep(u[s:].norm(), v[s:], depth+1, tmp, temps)
+	qhat = qhat.norm()
+	qhatv := tmp.make(3 * n)
+	qhatv.clear()
+	qhatv = qhatv.mul(qhat, v[:s])
+	// Set the correct remainder as before.
+	for i := 0; i < 2; i++ {
+		if e := qhatv.cmp(u.norm()); e > 0 {
+			subVW(qhat, qhat, 1)
+			c := subVV(qhatv[:s], qhatv[:s], v[:s])
+			if len(qhatv) > s {
+				subVW(qhatv[s:], qhatv[s:], c)
+			}
+			addAt(u[s:], v[s:], 0)
+		}
+	}
+	if qhatv.cmp(u.norm()) > 0 {
+		panic("impossible")
+	}
+	c := subVV(u[0:len(qhatv)], u[0:len(qhatv)], qhatv)
+	if c > 0 {
+		c = subVW(u[len(qhatv):], u[len(qhatv):], c)
+	}
+	if c > 0 {
+		panic("impossible")
+	}
+
+	// Done!
+	addAt(z, qhat.norm(), 0)
+}
diff --git a/contrib/go/_std_1.18/src/math/big/prime.go b/contrib/go/_std_1.18/src/math/big/prime.go
new file mode 100644
index 0000000000..d9a5f1ec96
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/prime.go
@@ -0,0 +1,320 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package big
+
+import "math/rand"
+
+// ProbablyPrime reports whether x is probably prime,
+// applying the Miller-Rabin test with n pseudorandomly chosen bases
+// as well as a Baillie-PSW test.
+//
+// If x is prime, ProbablyPrime returns true.
+// If x is chosen randomly and not prime, ProbablyPrime probably returns false.
+// The probability of returning true for a randomly chosen non-prime is at most ¼ⁿ.
+//
+// ProbablyPrime is 100% accurate for inputs less than 2⁶⁴.
+// See Menezes et al., Handbook of Applied Cryptography, 1997, pp. 145-149,
+// and FIPS 186-4 Appendix F for further discussion of the error probabilities.
+//
+// ProbablyPrime is not suitable for judging primes that an adversary may
+// have crafted to fool the test.
+//
+// As of Go 1.8, ProbablyPrime(0) is allowed and applies only a Baillie-PSW test.
+// Before Go 1.8, ProbablyPrime applied only the Miller-Rabin tests, and ProbablyPrime(0) panicked.
+func (x *Int) ProbablyPrime(n int) bool {
+	// Note regarding the doc comment above:
+	// It would be more precise to say that the Baillie-PSW test uses the
+	// extra strong Lucas test as its Lucas test, but since no one knows
+	// how to tell any of the Lucas tests apart inside a Baillie-PSW test
+	// (they all work equally well empirically), that detail need not be
+	// documented or implicitly guaranteed.
+	// The comment does avoid saying "the" Baillie-PSW test
+	// because of this general ambiguity.
+
+	if n < 0 {
+		panic("negative n for ProbablyPrime")
+	}
+	if x.neg || len(x.abs) == 0 {
+		return false
+	}
+
+	// primeBitMask records the primes < 64.
+	const primeBitMask uint64 = 1<<2 | 1<<3 | 1<<5 | 1<<7 |
+		1<<11 | 1<<13 | 1<<17 | 1<<19 | 1<<23 | 1<<29 | 1<<31 |
+		1<<37 | 1<<41 | 1<<43 | 1<<47 | 1<<53 | 1<<59 | 1<<61
+
+	w := x.abs[0]
+	if len(x.abs) == 1 && w < 64 {
+		return primeBitMask&(1<<w) != 0
+	}
+
+	if w&1 == 0 {
+		return false // x is even
+	}
+
+	const primesA = 3 * 5 * 7 * 11 * 13 * 17 * 19 * 23 * 37
+	const primesB = 29 * 31 * 41 * 43 * 47 * 53
+
+	var rA, rB uint32
+	switch _W {
+	case 32:
+		rA = uint32(x.abs.modW(primesA))
+		rB = uint32(x.abs.modW(primesB))
+	case 64:
+		r := x.abs.modW((primesA * primesB) & _M)
+		rA = uint32(r % primesA)
+		rB = uint32(r % primesB)
+	default:
+		panic("math/big: invalid word size")
+	}
+
+	if rA%3 == 0 || rA%5 == 0 || rA%7 == 0 || rA%11 == 0 || rA%13 == 0 || rA%17 == 0 || rA%19 == 0 || rA%23 == 0 || rA%37 == 0 ||
+		rB%29 == 0 || rB%31 == 0 || rB%41 == 0 || rB%43 == 0 || rB%47 == 0 || rB%53 == 0 {
+		return false
+	}
+
+	return x.abs.probablyPrimeMillerRabin(n+1, true) && x.abs.probablyPrimeLucas()
+}
+
+// probablyPrimeMillerRabin reports whether n passes reps rounds of the
+// Miller-Rabin primality test, using pseudo-randomly chosen bases.
+// If force2 is true, one of the rounds is forced to use base 2.
+// See Handbook of Applied Cryptography, p. 139, Algorithm 4.24.
+// The number n is known to be non-zero.
+func (n nat) probablyPrimeMillerRabin(reps int, force2 bool) bool {
+	nm1 := nat(nil).sub(n, natOne)
+	// determine q, k such that nm1 = q << k
+	k := nm1.trailingZeroBits()
+	q := nat(nil).shr(nm1, k)
+
+	nm3 := nat(nil).sub(nm1, natTwo)
+	rand := rand.New(rand.NewSource(int64(n[0])))
+
+	var x, y, quotient nat
+	nm3Len := nm3.bitLen()
+
+NextRandom:
+	for i := 0; i < reps; i++ {
+		if i == reps-1 && force2 {
+			x = x.set(natTwo)
+		} else {
+			x = x.random(rand, nm3, nm3Len)
+			x = x.add(x, natTwo)
+		}
+		y = y.expNN(x, q, n)
+		if y.cmp(natOne) == 0 || y.cmp(nm1) == 0 {
+			continue
+		}
+		for j := uint(1); j < k; j++ {
+			y = y.sqr(y)
+			quotient, y = quotient.div(y, y, n)
+			if y.cmp(nm1) == 0 {
+				continue NextRandom
+			}
+			if y.cmp(natOne) == 0 {
+				return false
+			}
+		}
+		return false
+	}
+
+	return true
+}
+
+// probablyPrimeLucas reports whether n passes the "almost extra strong" Lucas probable prime test,
+// using Baillie-OEIS parameter selection. This corresponds to "AESLPSP" on Jacobsen's tables (link below).
+// The combination of this test and a Miller-Rabin/Fermat test with base 2 gives a Baillie-PSW test.
+//
+// References:
+//
+// Baillie and Wagstaff, "Lucas Pseudoprimes", Mathematics of Computation 35(152),
+// October 1980, pp. 1391-1417, especially page 1401.
+// https://www.ams.org/journals/mcom/1980-35-152/S0025-5718-1980-0583518-6/S0025-5718-1980-0583518-6.pdf
+//
+// Grantham, "Frobenius Pseudoprimes", Mathematics of Computation 70(234),
+// March 2000, pp. 873-891.
+// https://www.ams.org/journals/mcom/2001-70-234/S0025-5718-00-01197-2/S0025-5718-00-01197-2.pdf
+//
+// Baillie, "Extra strong Lucas pseudoprimes", OEIS A217719, https://oeis.org/A217719.
+//
+// Jacobsen, "Pseudoprime Statistics, Tables, and Data", http://ntheory.org/pseudoprimes.html.
+//
+// Nicely, "The Baillie-PSW Primality Test", http://www.trnicely.net/misc/bpsw.html.
+// (Note that Nicely's definition of the "extra strong" test gives the wrong Jacobi condition,
+// as pointed out by Jacobsen.)
+//
+// Crandall and Pomerance, Prime Numbers: A Computational Perspective, 2nd ed.
+// Springer, 2005.
+func (n nat) probablyPrimeLucas() bool {
+	// Discard 0, 1.
+	if len(n) == 0 || n.cmp(natOne) == 0 {
+		return false
+	}
+	// Two is the only even prime.
+	// Already checked by caller, but here to allow testing in isolation.
+	if n[0]&1 == 0 {
+		return n.cmp(natTwo) == 0
+	}
+
+	// Baillie-OEIS "method C" for choosing D, P, Q,
+	// as in https://oeis.org/A217719/a217719.txt:
+	// try increasing P ≥ 3 such that D = P² - 4 (so Q = 1)
+	// until Jacobi(D, n) = -1.
+	// The search is expected to succeed for non-square n after just a few trials.
+	// After more than expected failures, check whether n is square
+	// (which would cause Jacobi(D, n) = 1 for all D not dividing n).
+	p := Word(3)
+	d := nat{1}
+	t1 := nat(nil) // temp
+	intD := &Int{abs: d}
+	intN := &Int{abs: n}
+	for ; ; p++ {
+		if p > 10000 {
+			// This is widely believed to be impossible.
+			// If we get a report, we'll want the exact number n.
+			panic("math/big: internal error: cannot find (D/n) = -1 for " + intN.String())
+		}
+		d[0] = p*p - 4
+		j := Jacobi(intD, intN)
+		if j == -1 {
+			break
+		}
+		if j == 0 {
+			// d = p²-4 = (p-2)(p+2).
+			// If (d/n) == 0 then d shares a prime factor with n.
+			// Since the loop proceeds in increasing p and starts with p-2==1,
+			// the shared prime factor must be p+2.
+			// If p+2 == n, then n is prime; otherwise p+2 is a proper factor of n.
+			return len(n) == 1 && n[0] == p+2
+		}
+		if p == 40 {
+			// We'll never find (d/n) = -1 if n is a square.
+			// If n is a non-square we expect to find a d in just a few attempts on average.
+			// After 40 attempts, take a moment to check if n is indeed a square.
+			t1 = t1.sqrt(n)
+			t1 = t1.sqr(t1)
+			if t1.cmp(n) == 0 {
+				return false
+			}
+		}
+	}
+
+	// Grantham definition of "extra strong Lucas pseudoprime", after Thm 2.3 on p. 876
+	// (D, P, Q above have become Δ, b, 1):
+	//
+	// Let U_n = U_n(b, 1), V_n = V_n(b, 1), and Δ = b²-4.
+	// An extra strong Lucas pseudoprime to base b is a composite n = 2^r s + Jacobi(Δ, n),
+	// where s is odd and gcd(n, 2*Δ) = 1, such that either (i) U_s ≡ 0 mod n and V_s ≡ ±2 mod n,
+	// or (ii) V_{2^t s} ≡ 0 mod n for some 0 ≤ t < r-1.
+	//
+	// We know gcd(n, Δ) = 1 or else we'd have found Jacobi(d, n) == 0 above.
+	// We know gcd(n, 2) = 1 because n is odd.
+	//
+	// Arrange s = (n - Jacobi(Δ, n)) / 2^r = (n+1) / 2^r.
+	s := nat(nil).add(n, natOne)
+	r := int(s.trailingZeroBits())
+	s = s.shr(s, uint(r))
+	nm2 := nat(nil).sub(n, natTwo) // n-2
+
+	// We apply the "almost extra strong" test, which checks the above conditions
+	// except for U_s ≡ 0 mod n, which allows us to avoid computing any U_k values.
+	// Jacobsen points out that maybe we should just do the full extra strong test:
+	// "It is also possible to recover U_n using Crandall and Pomerance equation 3.13:
+	// U_n = D^-1 (2V_{n+1} - PV_n) allowing us to run the full extra-strong test
+	// at the cost of a single modular inversion. This computation is easy and fast in GMP,
+	// so we can get the full extra-strong test at essentially the same performance as the
+	// almost extra strong test."
+
+	// Compute Lucas sequence V_s(b, 1), where:
+	//
+	//	V(0) = 2
+	//	V(1) = P
+	//	V(k) = P V(k-1) - Q V(k-2).
+	//
+	// (Remember that due to method C above, P = b, Q = 1.)
+	//
+	// In general V(k) = α^k + β^k, where α and β are roots of x² - Px + Q.
+	// Crandall and Pomerance (p.147) observe that for 0 ≤ j ≤ k,
+	//
+	//	V(j+k) = V(j)V(k) - V(k-j).
+	//
+	// So in particular, to quickly double the subscript:
+	//
+	//	V(2k) = V(k)² - 2
+	//	V(2k+1) = V(k) V(k+1) - P
+	//
+	// We can therefore start with k=0 and build up to k=s in log₂(s) steps.
+	natP := nat(nil).setWord(p)
+	vk := nat(nil).setWord(2)
+	vk1 := nat(nil).setWord(p)
+	t2 := nat(nil) // temp
+	for i := int(s.bitLen()); i >= 0; i-- {
+		if s.bit(uint(i)) != 0 {
+			// k' = 2k+1
+			// V(k') = V(2k+1) = V(k) V(k+1) - P.
+			t1 = t1.mul(vk, vk1)
+			t1 = t1.add(t1, n)
+			t1 = t1.sub(t1, natP)
+			t2, vk = t2.div(vk, t1, n)
+			// V(k'+1) = V(2k+2) = V(k+1)² - 2.
+			t1 = t1.sqr(vk1)
+			t1 = t1.add(t1, nm2)
+			t2, vk1 = t2.div(vk1, t1, n)
+		} else {
+			// k' = 2k
+			// V(k'+1) = V(2k+1) = V(k) V(k+1) - P.
+			t1 = t1.mul(vk, vk1)
+			t1 = t1.add(t1, n)
+			t1 = t1.sub(t1, natP)
+			t2, vk1 = t2.div(vk1, t1, n)
+			// V(k') = V(2k) = V(k)² - 2
+			t1 = t1.sqr(vk)
+			t1 = t1.add(t1, nm2)
+			t2, vk = t2.div(vk, t1, n)
+		}
+	}
+
+	// Now k=s, so vk = V(s). Check V(s) ≡ ±2 (mod n).
+	if vk.cmp(natTwo) == 0 || vk.cmp(nm2) == 0 {
+		// Check U(s) ≡ 0.
+		// As suggested by Jacobsen, apply Crandall and Pomerance equation 3.13:
+		//
+		//	U(k) = D⁻¹ (2 V(k+1) - P V(k))
+		//
+		// Since we are checking for U(k) == 0 it suffices to check 2 V(k+1) == P V(k) mod n,
+		// or P V(k) - 2 V(k+1) == 0 mod n.
+		t1 := t1.mul(vk, natP)
+		t2 := t2.shl(vk1, 1)
+		if t1.cmp(t2) < 0 {
+			t1, t2 = t2, t1
+		}
+		t1 = t1.sub(t1, t2)
+		t3 := vk1 // steal vk1, no longer needed below
+		vk1 = nil
+		_ = vk1
+		t2, t3 = t2.div(t3, t1, n)
+		if len(t3) == 0 {
+			return true
+		}
+	}
+
+	// Check V(2^t s) ≡ 0 mod n for some 0 ≤ t < r-1.
+	for t := 0; t < r-1; t++ {
+		if len(vk) == 0 { // vk == 0
+			return true
+		}
+		// Optimization: V(k) = 2 is a fixed point for V(k') = V(k)² - 2,
+		// so if V(k) = 2, we can stop: we will never find a future V(k) == 0.
+		if len(vk) == 1 && vk[0] == 2 { // vk == 2
+			return false
+		}
+		// k' = 2k
+		// V(k') = V(2k) = V(k)² - 2
+		t1 = t1.sqr(vk)
+		t1 = t1.sub(t1, natTwo)
+		t2, vk = t2.div(vk, t1, n)
+	}
+	return false
+}
diff --git a/contrib/go/_std_1.18/src/math/big/rat.go b/contrib/go/_std_1.18/src/math/big/rat.go
new file mode 100644
index 0000000000..731a979ff7
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/rat.go
@@ -0,0 +1,544 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements multi-precision rational numbers.
+
+package big
+
+import (
+	"fmt"
+	"math"
+)
+
+// A Rat represents a quotient a/b of arbitrary precision.
+// The zero value for a Rat represents the value 0.
+//
+// Operations always take pointer arguments (*Rat) rather
+// than Rat values, and each unique Rat value requires
+// its own unique *Rat pointer. To "copy" a Rat value,
+// an existing (or newly allocated) Rat must be set to
+// a new value using the Rat.Set method; shallow copies
+// of Rats are not supported and may lead to errors.
+type Rat struct {
+	// To make zero values for Rat work w/o initialization,
+	// a zero value of b (len(b) == 0) acts like b == 1. At
+	// the earliest opportunity (when an assignment to the Rat
+	// is made), such uninitialized denominators are set to 1.
+	// a.neg determines the sign of the Rat, b.neg is ignored.
+	a, b Int
+}
+
+// NewRat creates a new Rat with numerator a and denominator b.
+func NewRat(a, b int64) *Rat {
+	return new(Rat).SetFrac64(a, b)
+}
+
+// SetFloat64 sets z to exactly f and returns z.
+// If f is not finite, SetFloat returns nil.
+func (z *Rat) SetFloat64(f float64) *Rat {
+	const expMask = 1<<11 - 1
+	bits := math.Float64bits(f)
+	mantissa := bits & (1<<52 - 1)
+	exp := int((bits >> 52) & expMask)
+	switch exp {
+	case expMask: // non-finite
+		return nil
+	case 0: // denormal
+		exp -= 1022
+	default: // normal
+		mantissa |= 1 << 52
+		exp -= 1023
+	}
+
+	shift := 52 - exp
+
+	// Optimization (?): partially pre-normalise.
+	for mantissa&1 == 0 && shift > 0 {
+		mantissa >>= 1
+		shift--
+	}
+
+	z.a.SetUint64(mantissa)
+	z.a.neg = f < 0
+	z.b.Set(intOne)
+	if shift > 0 {
+		z.b.Lsh(&z.b, uint(shift))
+	} else {
+		z.a.Lsh(&z.a, uint(-shift))
+	}
+	return z.norm()
+}
+
+// quotToFloat32 returns the non-negative float32 value
+// nearest to the quotient a/b, using round-to-even in
+// halfway cases. It does not mutate its arguments.
+// Preconditions: b is non-zero; a and b have no common factors.
+func quotToFloat32(a, b nat) (f float32, exact bool) {
+	const (
+		// float size in bits
+		Fsize = 32
+
+		// mantissa
+		Msize  = 23
+		Msize1 = Msize + 1 // incl. implicit 1
+		Msize2 = Msize1 + 1
+
+		// exponent
+		Esize = Fsize - Msize1
+		Ebias = 1<<(Esize-1) - 1
+		Emin  = 1 - Ebias
+		Emax  = Ebias
+	)
+
+	// TODO(adonovan): specialize common degenerate cases: 1.0, integers.
+	alen := a.bitLen()
+	if alen == 0 {
+		return 0, true
+	}
+	blen := b.bitLen()
+	if blen == 0 {
+		panic("division by zero")
+	}
+
+	// 1. Left-shift A or B such that quotient A/B is in [1<<Msize1, 1<<(Msize2+1)
+	// (Msize2 bits if A < B when they are left-aligned, Msize2+1 bits if A >= B).
+	// This is 2 or 3 more than the float32 mantissa field width of Msize:
+	// - the optional extra bit is shifted away in step 3 below.
+	// - the high-order 1 is omitted in "normal" representation;
+	// - the low-order 1 will be used during rounding then discarded.
+	exp := alen - blen
+	var a2, b2 nat
+	a2 = a2.set(a)
+	b2 = b2.set(b)
+	if shift := Msize2 - exp; shift > 0 {
+		a2 = a2.shl(a2, uint(shift))
+	} else if shift < 0 {
+		b2 = b2.shl(b2, uint(-shift))
+	}
+
+	// 2. Compute quotient and remainder (q, r).  NB: due to the
+	// extra shift, the low-order bit of q is logically the
+	// high-order bit of r.
+	var q nat
+	q, r := q.div(a2, a2, b2) // (recycle a2)
+	mantissa := low32(q)
+	haveRem := len(r) > 0 // mantissa&1 && !haveRem => remainder is exactly half
+
+	// 3. If quotient didn't fit in Msize2 bits, redo division by b2<<1
+	// (in effect---we accomplish this incrementally).
+	if mantissa>>Msize2 == 1 {
+		if mantissa&1 == 1 {
+			haveRem = true
+		}
+		mantissa >>= 1
+		exp++
+	}
+	if mantissa>>Msize1 != 1 {
+		panic(fmt.Sprintf("expected exactly %d bits of result", Msize2))
+	}
+
+	// 4. Rounding.
+	if Emin-Msize <= exp && exp <= Emin {
+		// Denormal case; lose 'shift' bits of precision.
+		shift := uint(Emin - (exp - 1)) // [1..Esize1)
+		lostbits := mantissa & (1<<shift - 1)
+		haveRem = haveRem || lostbits != 0
+		mantissa >>= shift
+		exp = 2 - Ebias // == exp + shift
+	}
+	// Round q using round-half-to-even.
+	exact = !haveRem
+	if mantissa&1 != 0 {
+		exact = false
+		if haveRem || mantissa&2 != 0 {
+			if mantissa++; mantissa >= 1<<Msize2 {
+				// Complete rollover 11...1 => 100...0, so shift is safe
+				mantissa >>= 1
+				exp++
+			}
+		}
+	}
+	mantissa >>= 1 // discard rounding bit.  Mantissa now scaled by 1<<Msize1.
+
+	f = float32(math.Ldexp(float64(mantissa), exp-Msize1))
+	if math.IsInf(float64(f), 0) {
+		exact = false
+	}
+	return
+}
+
+// quotToFloat64 returns the non-negative float64 value
+// nearest to the quotient a/b, using round-to-even in
+// halfway cases. It does not mutate its arguments.
+// Preconditions: b is non-zero; a and b have no common factors.
+func quotToFloat64(a, b nat) (f float64, exact bool) {
+	const (
+		// float size in bits
+		Fsize = 64
+
+		// mantissa
+		Msize  = 52
+		Msize1 = Msize + 1 // incl. implicit 1
+		Msize2 = Msize1 + 1
+
+		// exponent
+		Esize = Fsize - Msize1
+		Ebias = 1<<(Esize-1) - 1
+		Emin  = 1 - Ebias
+		Emax  = Ebias
+	)
+
+	// TODO(adonovan): specialize common degenerate cases: 1.0, integers.
+	alen := a.bitLen()
+	if alen == 0 {
+		return 0, true
+	}
+	blen := b.bitLen()
+	if blen == 0 {
+		panic("division by zero")
+	}
+
+	// 1. Left-shift A or B such that quotient A/B is in [1<<Msize1, 1<<(Msize2+1)
+	// (Msize2 bits if A < B when they are left-aligned, Msize2+1 bits if A >= B).
+	// This is 2 or 3 more than the float64 mantissa field width of Msize:
+	// - the optional extra bit is shifted away in step 3 below.
+	// - the high-order 1 is omitted in "normal" representation;
+	// - the low-order 1 will be used during rounding then discarded.
+	exp := alen - blen
+	var a2, b2 nat
+	a2 = a2.set(a)
+	b2 = b2.set(b)
+	if shift := Msize2 - exp; shift > 0 {
+		a2 = a2.shl(a2, uint(shift))
+	} else if shift < 0 {
+		b2 = b2.shl(b2, uint(-shift))
+	}
+
+	// 2. Compute quotient and remainder (q, r).  NB: due to the
+	// extra shift, the low-order bit of q is logically the
+	// high-order bit of r.
+	var q nat
+	q, r := q.div(a2, a2, b2) // (recycle a2)
+	mantissa := low64(q)
+	haveRem := len(r) > 0 // mantissa&1 && !haveRem => remainder is exactly half
+
+	// 3. If quotient didn't fit in Msize2 bits, redo division by b2<<1
+	// (in effect---we accomplish this incrementally).
+	if mantissa>>Msize2 == 1 {
+		if mantissa&1 == 1 {
+			haveRem = true
+		}
+		mantissa >>= 1
+		exp++
+	}
+	if mantissa>>Msize1 != 1 {
+		panic(fmt.Sprintf("expected exactly %d bits of result", Msize2))
+	}
+
+	// 4. Rounding.
+	if Emin-Msize <= exp && exp <= Emin {
+		// Denormal case; lose 'shift' bits of precision.
+		shift := uint(Emin - (exp - 1)) // [1..Esize1)
+		lostbits := mantissa & (1<<shift - 1)
+		haveRem = haveRem || lostbits != 0
+		mantissa >>= shift
+		exp = 2 - Ebias // == exp + shift
+	}
+	// Round q using round-half-to-even.
+	exact = !haveRem
+	if mantissa&1 != 0 {
+		exact = false
+		if haveRem || mantissa&2 != 0 {
+			if mantissa++; mantissa >= 1<<Msize2 {
+				// Complete rollover 11...1 => 100...0, so shift is safe
+				mantissa >>= 1
+				exp++
+			}
+		}
+	}
+	mantissa >>= 1 // discard rounding bit.  Mantissa now scaled by 1<<Msize1.
+
+	f = math.Ldexp(float64(mantissa), exp-Msize1)
+	if math.IsInf(f, 0) {
+		exact = false
+	}
+	return
+}
+
+// Float32 returns the nearest float32 value for x and a bool indicating
+// whether f represents x exactly. If the magnitude of x is too large to
+// be represented by a float32, f is an infinity and exact is false.
+// The sign of f always matches the sign of x, even if f == 0.
+func (x *Rat) Float32() (f float32, exact bool) {
+	b := x.b.abs
+	if len(b) == 0 {
+		b = natOne
+	}
+	f, exact = quotToFloat32(x.a.abs, b)
+	if x.a.neg {
+		f = -f
+	}
+	return
+}
+
+// Float64 returns the nearest float64 value for x and a bool indicating
+// whether f represents x exactly. If the magnitude of x is too large to
+// be represented by a float64, f is an infinity and exact is false.
+// The sign of f always matches the sign of x, even if f == 0.
+func (x *Rat) Float64() (f float64, exact bool) {
+	b := x.b.abs
+	if len(b) == 0 {
+		b = natOne
+	}
+	f, exact = quotToFloat64(x.a.abs, b)
+	if x.a.neg {
+		f = -f
+	}
+	return
+}
+
+// SetFrac sets z to a/b and returns z.
+// If b == 0, SetFrac panics.
+func (z *Rat) SetFrac(a, b *Int) *Rat {
+	z.a.neg = a.neg != b.neg
+	babs := b.abs
+	if len(babs) == 0 {
+		panic("division by zero")
+	}
+	if &z.a == b || alias(z.a.abs, babs) {
+		babs = nat(nil).set(babs) // make a copy
+	}
+	z.a.abs = z.a.abs.set(a.abs)
+	z.b.abs = z.b.abs.set(babs)
+	return z.norm()
+}
+
+// SetFrac64 sets z to a/b and returns z.
+// If b == 0, SetFrac64 panics.
+func (z *Rat) SetFrac64(a, b int64) *Rat {
+	if b == 0 {
+		panic("division by zero")
+	}
+	z.a.SetInt64(a)
+	if b < 0 {
+		b = -b
+		z.a.neg = !z.a.neg
+	}
+	z.b.abs = z.b.abs.setUint64(uint64(b))
+	return z.norm()
+}
+
+// SetInt sets z to x (by making a copy of x) and returns z.
+func (z *Rat) SetInt(x *Int) *Rat {
+	z.a.Set(x)
+	z.b.abs = z.b.abs.setWord(1)
+	return z
+}
+
+// SetInt64 sets z to x and returns z.
+func (z *Rat) SetInt64(x int64) *Rat {
+	z.a.SetInt64(x)
+	z.b.abs = z.b.abs.setWord(1)
+	return z
+}
+
+// SetUint64 sets z to x and returns z.
+func (z *Rat) SetUint64(x uint64) *Rat {
+	z.a.SetUint64(x)
+	z.b.abs = z.b.abs.setWord(1)
+	return z
+}
+
+// Set sets z to x (by making a copy of x) and returns z.
+func (z *Rat) Set(x *Rat) *Rat {
+	if z != x {
+		z.a.Set(&x.a)
+		z.b.Set(&x.b)
+	}
+	if len(z.b.abs) == 0 {
+		z.b.abs = z.b.abs.setWord(1)
+	}
+	return z
+}
+
+// Abs sets z to |x| (the absolute value of x) and returns z.
+func (z *Rat) Abs(x *Rat) *Rat {
+	z.Set(x)
+	z.a.neg = false
+	return z
+}
+
+// Neg sets z to -x and returns z.
+func (z *Rat) Neg(x *Rat) *Rat {
+	z.Set(x)
+	z.a.neg = len(z.a.abs) > 0 && !z.a.neg // 0 has no sign
+	return z
+}
+
+// Inv sets z to 1/x and returns z.
+// If x == 0, Inv panics.
+func (z *Rat) Inv(x *Rat) *Rat {
+	if len(x.a.abs) == 0 {
+		panic("division by zero")
+	}
+	z.Set(x)
+	z.a.abs, z.b.abs = z.b.abs, z.a.abs
+	return z
+}
+
+// Sign returns:
+//
+//	-1 if x <  0
+//	 0 if x == 0
+//	+1 if x >  0
+//
+func (x *Rat) Sign() int {
+	return x.a.Sign()
+}
+
+// IsInt reports whether the denominator of x is 1.
+func (x *Rat) IsInt() bool {
+	return len(x.b.abs) == 0 || x.b.abs.cmp(natOne) == 0
+}
+
+// Num returns the numerator of x; it may be <= 0.
+// The result is a reference to x's numerator; it
+// may change if a new value is assigned to x, and vice versa.
+// The sign of the numerator corresponds to the sign of x.
+func (x *Rat) Num() *Int {
+	return &x.a
+}
+
+// Denom returns the denominator of x; it is always > 0.
+// The result is a reference to x's denominator, unless
+// x is an uninitialized (zero value) Rat, in which case
+// the result is a new Int of value 1. (To initialize x,
+// any operation that sets x will do, including x.Set(x).)
+// If the result is a reference to x's denominator it
+// may change if a new value is assigned to x, and vice versa.
+func (x *Rat) Denom() *Int {
+	// Note that x.b.neg is guaranteed false.
+	if len(x.b.abs) == 0 {
+		// Note: If this proves problematic, we could
+		//       panic instead and require the Rat to
+		//       be explicitly initialized.
+		return &Int{abs: nat{1}}
+	}
+	return &x.b
+}
+
+func (z *Rat) norm() *Rat {
+	switch {
+	case len(z.a.abs) == 0:
+		// z == 0; normalize sign and denominator
+		z.a.neg = false
+		fallthrough
+	case len(z.b.abs) == 0:
+		// z is integer; normalize denominator
+		z.b.abs = z.b.abs.setWord(1)
+	default:
+		// z is fraction; normalize numerator and denominator
+		neg := z.a.neg
+		z.a.neg = false
+		z.b.neg = false
+		if f := NewInt(0).lehmerGCD(nil, nil, &z.a, &z.b); f.Cmp(intOne) != 0 {
+			z.a.abs, _ = z.a.abs.div(nil, z.a.abs, f.abs)
+			z.b.abs, _ = z.b.abs.div(nil, z.b.abs, f.abs)
+		}
+		z.a.neg = neg
+	}
+	return z
+}
+
+// mulDenom sets z to the denominator product x*y (by taking into
+// account that 0 values for x or y must be interpreted as 1) and
+// returns z.
+func mulDenom(z, x, y nat) nat {
+	switch {
+	case len(x) == 0 && len(y) == 0:
+		return z.setWord(1)
+	case len(x) == 0:
+		return z.set(y)
+	case len(y) == 0:
+		return z.set(x)
+	}
+	return z.mul(x, y)
+}
+
+// scaleDenom sets z to the product x*f.
+// If f == 0 (zero value of denominator), z is set to (a copy of) x.
+func (z *Int) scaleDenom(x *Int, f nat) {
+	if len(f) == 0 {
+		z.Set(x)
+		return
+	}
+	z.abs = z.abs.mul(x.abs, f)
+	z.neg = x.neg
+}
+
+// Cmp compares x and y and returns:
+//
+//   -1 if x <  y
+//    0 if x == y
+//   +1 if x >  y
+//
+func (x *Rat) Cmp(y *Rat) int {
+	var a, b Int
+	a.scaleDenom(&x.a, y.b.abs)
+	b.scaleDenom(&y.a, x.b.abs)
+	return a.Cmp(&b)
+}
+
+// Add sets z to the sum x+y and returns z.
+func (z *Rat) Add(x, y *Rat) *Rat {
+	var a1, a2 Int
+	a1.scaleDenom(&x.a, y.b.abs)
+	a2.scaleDenom(&y.a, x.b.abs)
+	z.a.Add(&a1, &a2)
+	z.b.abs = mulDenom(z.b.abs, x.b.abs, y.b.abs)
+	return z.norm()
+}
+
+// Sub sets z to the difference x-y and returns z.
+func (z *Rat) Sub(x, y *Rat) *Rat {
+	var a1, a2 Int
+	a1.scaleDenom(&x.a, y.b.abs)
+	a2.scaleDenom(&y.a, x.b.abs)
+	z.a.Sub(&a1, &a2)
+	z.b.abs = mulDenom(z.b.abs, x.b.abs, y.b.abs)
+	return z.norm()
+}
+
+// Mul sets z to the product x*y and returns z.
+func (z *Rat) Mul(x, y *Rat) *Rat {
+	if x == y {
+		// a squared Rat is positive and can't be reduced (no need to call norm())
+		z.a.neg = false
+		z.a.abs = z.a.abs.sqr(x.a.abs)
+		if len(x.b.abs) == 0 {
+			z.b.abs = z.b.abs.setWord(1)
+		} else {
+			z.b.abs = z.b.abs.sqr(x.b.abs)
+		}
+		return z
+	}
+	z.a.Mul(&x.a, &y.a)
+	z.b.abs = mulDenom(z.b.abs, x.b.abs, y.b.abs)
+	return z.norm()
+}
+
+// Quo sets z to the quotient x/y and returns z.
+// If y == 0, Quo panics.
+func (z *Rat) Quo(x, y *Rat) *Rat {
+	if len(y.a.abs) == 0 {
+		panic("division by zero")
+	}
+	var a, b Int
+	a.scaleDenom(&x.a, y.b.abs)
+	b.scaleDenom(&y.a, x.b.abs)
+	z.a.abs = a.abs
+	z.b.abs = b.abs
+	z.a.neg = a.neg != b.neg
+	return z.norm()
+}
diff --git a/contrib/go/_std_1.18/src/math/big/ratconv.go b/contrib/go/_std_1.18/src/math/big/ratconv.go
new file mode 100644
index 0000000000..90053a9c81
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/ratconv.go
@@ -0,0 +1,380 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements rat-to-string conversion functions.
+
+package big
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+)
+
+func ratTok(ch rune) bool {
+	return strings.ContainsRune("+-/0123456789.eE", ch)
+}
+
+var ratZero Rat
+var _ fmt.Scanner = &ratZero // *Rat must implement fmt.Scanner
+
+// Scan is a support routine for fmt.Scanner. It accepts the formats
+// 'e', 'E', 'f', 'F', 'g', 'G', and 'v'. All formats are equivalent.
+func (z *Rat) Scan(s fmt.ScanState, ch rune) error {
+	tok, err := s.Token(true, ratTok)
+	if err != nil {
+		return err
+	}
+	if !strings.ContainsRune("efgEFGv", ch) {
+		return errors.New("Rat.Scan: invalid verb")
+	}
+	if _, ok := z.SetString(string(tok)); !ok {
+		return errors.New("Rat.Scan: invalid syntax")
+	}
+	return nil
+}
+
+// SetString sets z to the value of s and returns z and a boolean indicating
+// success. s can be given as a (possibly signed) fraction "a/b", or as a
+// floating-point number optionally followed by an exponent.
+// If a fraction is provided, both the dividend and the divisor may be a
+// decimal integer or independently use a prefix of ``0b'', ``0'' or ``0o'',
+// or ``0x'' (or their upper-case variants) to denote a binary, octal, or
+// hexadecimal integer, respectively. The divisor may not be signed.
+// If a floating-point number is provided, it may be in decimal form or
+// use any of the same prefixes as above but for ``0'' to denote a non-decimal
+// mantissa. A leading ``0'' is considered a decimal leading 0; it does not
+// indicate octal representation in this case.
+// An optional base-10 ``e'' or base-2 ``p'' (or their upper-case variants)
+// exponent may be provided as well, except for hexadecimal floats which
+// only accept an (optional) ``p'' exponent (because an ``e'' or ``E'' cannot
+// be distinguished from a mantissa digit). If the exponent's absolute value
+// is too large, the operation may fail.
+// The entire string, not just a prefix, must be valid for success. If the
+// operation failed, the value of z is undefined but the returned value is nil.
+func (z *Rat) SetString(s string) (*Rat, bool) {
+	if len(s) == 0 {
+		return nil, false
+	}
+	// len(s) > 0
+
+	// parse fraction a/b, if any
+	if sep := strings.Index(s, "/"); sep >= 0 {
+		if _, ok := z.a.SetString(s[:sep], 0); !ok {
+			return nil, false
+		}
+		r := strings.NewReader(s[sep+1:])
+		var err error
+		if z.b.abs, _, _, err = z.b.abs.scan(r, 0, false); err != nil {
+			return nil, false
+		}
+		// entire string must have been consumed
+		if _, err = r.ReadByte(); err != io.EOF {
+			return nil, false
+		}
+		if len(z.b.abs) == 0 {
+			return nil, false
+		}
+		return z.norm(), true
+	}
+
+	// parse floating-point number
+	r := strings.NewReader(s)
+
+	// sign
+	neg, err := scanSign(r)
+	if err != nil {
+		return nil, false
+	}
+
+	// mantissa
+	var base int
+	var fcount int // fractional digit count; valid if <= 0
+	z.a.abs, base, fcount, err = z.a.abs.scan(r, 0, true)
+	if err != nil {
+		return nil, false
+	}
+
+	// exponent
+	var exp int64
+	var ebase int
+	exp, ebase, err = scanExponent(r, true, true)
+	if err != nil {
+		return nil, false
+	}
+
+	// there should be no unread characters left
+	if _, err = r.ReadByte(); err != io.EOF {
+		return nil, false
+	}
+
+	// special-case 0 (see also issue #16176)
+	if len(z.a.abs) == 0 {
+		return z, true
+	}
+	// len(z.a.abs) > 0
+
+	// The mantissa may have a radix point (fcount <= 0) and there
+	// may be a nonzero exponent exp. The radix point amounts to a
+	// division by base**(-fcount), which equals a multiplication by
+	// base**fcount. An exponent means multiplication by ebase**exp.
+	// Multiplications are commutative, so we can apply them in any
+	// order. We only have powers of 2 and 10, and we split powers
+	// of 10 into the product of the same powers of 2 and 5. This
+	// may reduce the size of shift/multiplication factors or
+	// divisors required to create the final fraction, depending
+	// on the actual floating-point value.
+
+	// determine binary or decimal exponent contribution of radix point
+	var exp2, exp5 int64
+	if fcount < 0 {
+		// The mantissa has a radix point ddd.dddd; and
+		// -fcount is the number of digits to the right
+		// of '.'. Adjust relevant exponent accordingly.
+		d := int64(fcount)
+		switch base {
+		case 10:
+			exp5 = d
+			fallthrough // 10**e == 5**e * 2**e
+		case 2:
+			exp2 = d
+		case 8:
+			exp2 = d * 3 // octal digits are 3 bits each
+		case 16:
+			exp2 = d * 4 // hexadecimal digits are 4 bits each
+		default:
+			panic("unexpected mantissa base")
+		}
+		// fcount consumed - not needed anymore
+	}
+
+	// take actual exponent into account
+	switch ebase {
+	case 10:
+		exp5 += exp
+		fallthrough // see fallthrough above
+	case 2:
+		exp2 += exp
+	default:
+		panic("unexpected exponent base")
+	}
+	// exp consumed - not needed anymore
+
+	// apply exp5 contributions
+	// (start with exp5 so the numbers to multiply are smaller)
+	if exp5 != 0 {
+		n := exp5
+		if n < 0 {
+			n = -n
+			if n < 0 {
+				// This can occur if -n overflows. -(-1 << 63) would become
+				// -1 << 63, which is still negative.
+				return nil, false
+			}
+		}
+		if n > 1e6 {
+			return nil, false // avoid excessively large exponents
+		}
+		pow5 := z.b.abs.expNN(natFive, nat(nil).setWord(Word(n)), nil) // use underlying array of z.b.abs
+		if exp5 > 0 {
+			z.a.abs = z.a.abs.mul(z.a.abs, pow5)
+			z.b.abs = z.b.abs.setWord(1)
+		} else {
+			z.b.abs = pow5
+		}
+	} else {
+		z.b.abs = z.b.abs.setWord(1)
+	}
+
+	// apply exp2 contributions
+	if exp2 < -1e7 || exp2 > 1e7 {
+		return nil, false // avoid excessively large exponents
+	}
+	if exp2 > 0 {
+		z.a.abs = z.a.abs.shl(z.a.abs, uint(exp2))
+	} else if exp2 < 0 {
+		z.b.abs = z.b.abs.shl(z.b.abs, uint(-exp2))
+	}
+
+	z.a.neg = neg && len(z.a.abs) > 0 // 0 has no sign
+
+	return z.norm(), true
+}
+
+// scanExponent scans the longest possible prefix of r representing a base 10
+// (``e'', ``E'') or a base 2 (``p'', ``P'') exponent, if any. It returns the
+// exponent, the exponent base (10 or 2), or a read or syntax error, if any.
+//
+// If sepOk is set, an underscore character ``_'' may appear between successive
+// exponent digits; such underscores do not change the value of the exponent.
+// Incorrect placement of underscores is reported as an error if there are no
+// other errors. If sepOk is not set, underscores are not recognized and thus
+// terminate scanning like any other character that is not a valid digit.
+//
+//	exponent = ( "e" | "E" | "p" | "P" ) [ sign ] digits .
+//	sign     = "+" | "-" .
+//	digits   = digit { [ '_' ] digit } .
+//	digit    = "0" ... "9" .
+//
+// A base 2 exponent is only permitted if base2ok is set.
+func scanExponent(r io.ByteScanner, base2ok, sepOk bool) (exp int64, base int, err error) {
+	// one char look-ahead
+	ch, err := r.ReadByte()
+	if err != nil {
+		if err == io.EOF {
+			err = nil
+		}
+		return 0, 10, err
+	}
+
+	// exponent char
+	switch ch {
+	case 'e', 'E':
+		base = 10
+	case 'p', 'P':
+		if base2ok {
+			base = 2
+			break // ok
+		}
+		fallthrough // binary exponent not permitted
+	default:
+		r.UnreadByte() // ch does not belong to exponent anymore
+		return 0, 10, nil
+	}
+
+	// sign
+	var digits []byte
+	ch, err = r.ReadByte()
+	if err == nil && (ch == '+' || ch == '-') {
+		if ch == '-' {
+			digits = append(digits, '-')
+		}
+		ch, err = r.ReadByte()
+	}
+
+	// prev encodes the previously seen char: it is one
+	// of '_', '0' (a digit), or '.' (anything else). A
+	// valid separator '_' may only occur after a digit.
+	prev := '.'
+	invalSep := false
+
+	// exponent value
+	hasDigits := false
+	for err == nil {
+		if '0' <= ch && ch <= '9' {
+			digits = append(digits, ch)
+			prev = '0'
+			hasDigits = true
+		} else if ch == '_' && sepOk {
+			if prev != '0' {
+				invalSep = true
+			}
+			prev = '_'
+		} else {
+			r.UnreadByte() // ch does not belong to number anymore
+			break
+		}
+		ch, err = r.ReadByte()
+	}
+
+	if err == io.EOF {
+		err = nil
+	}
+	if err == nil && !hasDigits {
+		err = errNoDigits
+	}
+	if err == nil {
+		exp, err = strconv.ParseInt(string(digits), 10, 64)
+	}
+	// other errors take precedence over invalid separators
+	if err == nil && (invalSep || prev == '_') {
+		err = errInvalSep
+	}
+
+	return
+}
+
+// String returns a string representation of x in the form "a/b" (even if b == 1).
+func (x *Rat) String() string {
+	return string(x.marshal())
+}
+
+// marshal implements String returning a slice of bytes
+func (x *Rat) marshal() []byte {
+	var buf []byte
+	buf = x.a.Append(buf, 10)
+	buf = append(buf, '/')
+	if len(x.b.abs) != 0 {
+		buf = x.b.Append(buf, 10)
+	} else {
+		buf = append(buf, '1')
+	}
+	return buf
+}
+
+// RatString returns a string representation of x in the form "a/b" if b != 1,
+// and in the form "a" if b == 1.
+func (x *Rat) RatString() string {
+	if x.IsInt() {
+		return x.a.String()
+	}
+	return x.String()
+}
+
+// FloatString returns a string representation of x in decimal form with prec
+// digits of precision after the radix point. The last digit is rounded to
+// nearest, with halves rounded away from zero.
+func (x *Rat) FloatString(prec int) string {
+	var buf []byte
+
+	if x.IsInt() {
+		buf = x.a.Append(buf, 10)
+		if prec > 0 {
+			buf = append(buf, '.')
+			for i := prec; i > 0; i-- {
+				buf = append(buf, '0')
+			}
+		}
+		return string(buf)
+	}
+	// x.b.abs != 0
+
+	q, r := nat(nil).div(nat(nil), x.a.abs, x.b.abs)
+
+	p := natOne
+	if prec > 0 {
+		p = nat(nil).expNN(natTen, nat(nil).setUint64(uint64(prec)), nil)
+	}
+
+	r = r.mul(r, p)
+	r, r2 := r.div(nat(nil), r, x.b.abs)
+
+	// see if we need to round up
+	r2 = r2.add(r2, r2)
+	if x.b.abs.cmp(r2) <= 0 {
+		r = r.add(r, natOne)
+		if r.cmp(p) >= 0 {
+			q = nat(nil).add(q, natOne)
+			r = nat(nil).sub(r, p)
+		}
+	}
+
+	if x.a.neg {
+		buf = append(buf, '-')
+	}
+	buf = append(buf, q.utoa(10)...) // itoa ignores sign if q == 0
+
+	if prec > 0 {
+		buf = append(buf, '.')
+		rs := r.utoa(10)
+		for i := prec - len(rs); i > 0; i-- {
+			buf = append(buf, '0')
+		}
+		buf = append(buf, rs...)
+	}
+
+	return string(buf)
+}
diff --git a/contrib/go/_std_1.18/src/math/big/ratmarsh.go b/contrib/go/_std_1.18/src/math/big/ratmarsh.go
new file mode 100644
index 0000000000..fbc7b6002d
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/ratmarsh.go
@@ -0,0 +1,75 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements encoding/decoding of Rats.
+
+package big
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+)
+
+// Gob codec version. Permits backward-compatible changes to the encoding.
+const ratGobVersion byte = 1
+
+// GobEncode implements the gob.GobEncoder interface.
+func (x *Rat) GobEncode() ([]byte, error) {
+	if x == nil {
+		return nil, nil
+	}
+	buf := make([]byte, 1+4+(len(x.a.abs)+len(x.b.abs))*_S) // extra bytes for version and sign bit (1), and numerator length (4)
+	i := x.b.abs.bytes(buf)
+	j := x.a.abs.bytes(buf[:i])
+	n := i - j
+	if int(uint32(n)) != n {
+		// this should never happen
+		return nil, errors.New("Rat.GobEncode: numerator too large")
+	}
+	binary.BigEndian.PutUint32(buf[j-4:j], uint32(n))
+	j -= 1 + 4
+	b := ratGobVersion << 1 // make space for sign bit
+	if x.a.neg {
+		b |= 1
+	}
+	buf[j] = b
+	return buf[j:], nil
+}
+
+// GobDecode implements the gob.GobDecoder interface.
+func (z *Rat) GobDecode(buf []byte) error {
+	if len(buf) == 0 {
+		// Other side sent a nil or default value.
+		*z = Rat{}
+		return nil
+	}
+	b := buf[0]
+	if b>>1 != ratGobVersion {
+		return fmt.Errorf("Rat.GobDecode: encoding version %d not supported", b>>1)
+	}
+	const j = 1 + 4
+	i := j + binary.BigEndian.Uint32(buf[j-4:j])
+	z.a.neg = b&1 != 0
+	z.a.abs = z.a.abs.setBytes(buf[j:i])
+	z.b.abs = z.b.abs.setBytes(buf[i:])
+	return nil
+}
+
+// MarshalText implements the encoding.TextMarshaler interface.
+func (x *Rat) MarshalText() (text []byte, err error) {
+	if x.IsInt() {
+		return x.a.MarshalText()
+	}
+	return x.marshal(), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface.
+func (z *Rat) UnmarshalText(text []byte) error {
+	// TODO(gri): get rid of the []byte/string conversion
+	if _, ok := z.SetString(string(text)); !ok {
+		return fmt.Errorf("math/big: cannot unmarshal %q into a *big.Rat", text)
+	}
+	return nil
+}
diff --git a/contrib/go/_std_1.18/src/math/big/roundingmode_string.go b/contrib/go/_std_1.18/src/math/big/roundingmode_string.go
new file mode 100644
index 0000000000..c7629eb98b
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/roundingmode_string.go
@@ -0,0 +1,16 @@
+// Code generated by "stringer -type=RoundingMode"; DO NOT EDIT.
+
+package big
+
+import "strconv"
+
+const _RoundingMode_name = "ToNearestEvenToNearestAwayToZeroAwayFromZeroToNegativeInfToPositiveInf"
+
+var _RoundingMode_index = [...]uint8{0, 13, 26, 32, 44, 57, 70}
+
+func (i RoundingMode) String() string {
+	if i >= RoundingMode(len(_RoundingMode_index)-1) {
+		return "RoundingMode(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _RoundingMode_name[_RoundingMode_index[i]:_RoundingMode_index[i+1]]
+}
diff --git a/contrib/go/_std_1.18/src/math/big/sqrt.go b/contrib/go/_std_1.18/src/math/big/sqrt.go
new file mode 100644
index 0000000000..0d50164557
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/big/sqrt.go
@@ -0,0 +1,128 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package big
+
+import (
+	"math"
+	"sync"
+)
+
+var threeOnce struct {
+	sync.Once
+	v *Float
+}
+
+func three() *Float {
+	threeOnce.Do(func() {
+		threeOnce.v = NewFloat(3.0)
+	})
+	return threeOnce.v
+}
+
+// Sqrt sets z to the rounded square root of x, and returns it.
+//
+// If z's precision is 0, it is changed to x's precision before the
+// operation. Rounding is performed according to z's precision and
+// rounding mode, but z's accuracy is not computed. Specifically, the
+// result of z.Acc() is undefined.
+//
+// The function panics if z < 0. The value of z is undefined in that
+// case.
+func (z *Float) Sqrt(x *Float) *Float {
+	if debugFloat {
+		x.validate()
+	}
+
+	if z.prec == 0 {
+		z.prec = x.prec
+	}
+
+	if x.Sign() == -1 {
+		// following IEEE754-2008 (section 7.2)
+		panic(ErrNaN{"square root of negative operand"})
+	}
+
+	// handle ±0 and +∞
+	if x.form != finite {
+		z.acc = Exact
+		z.form = x.form
+		z.neg = x.neg // IEEE754-2008 requires √±0 = ±0
+		return z
+	}
+
+	// MantExp sets the argument's precision to the receiver's, and
+	// when z.prec > x.prec this will lower z.prec. Restore it after
+	// the MantExp call.
+	prec := z.prec
+	b := x.MantExp(z)
+	z.prec = prec
+
+	// Compute √(z·2**b) as
+	//   √( z)·2**(½b)     if b is even
+	//   √(2z)·2**(⌊½b⌋)   if b > 0 is odd
+	//   √(½z)·2**(⌈½b⌉)   if b < 0 is odd
+	switch b % 2 {
+	case 0:
+		// nothing to do
+	case 1:
+		z.exp++
+	case -1:
+		z.exp--
+	}
+	// 0.25 <= z < 2.0
+
+	// Solving 1/x² - z = 0 avoids Quo calls and is faster, especially
+	// for high precisions.
+	z.sqrtInverse(z)
+
+	// re-attach halved exponent
+	return z.SetMantExp(z, b/2)
+}
+
+// Compute √x (to z.prec precision) by solving
+//   1/t² - x = 0
+// for t (using Newton's method), and then inverting.
+func (z *Float) sqrtInverse(x *Float) {
+	// let
+	//   f(t) = 1/t² - x
+	// then
+	//   g(t) = f(t)/f'(t) = -½t(1 - xt²)
+	// and the next guess is given by
+	//   t2 = t - g(t) = ½t(3 - xt²)
+	u := newFloat(z.prec)
+	v := newFloat(z.prec)
+	three := three()
+	ng := func(t *Float) *Float {
+		u.prec = t.prec
+		v.prec = t.prec
+		u.Mul(t, t)     // u = t²
+		u.Mul(x, u)     //   = xt²
+		v.Sub(three, u) // v = 3 - xt²
+		u.Mul(t, v)     // u = t(3 - xt²)
+		u.exp--         //   = ½t(3 - xt²)
+		return t.Set(u)
+	}
+
+	xf, _ := x.Float64()
+	sqi := newFloat(z.prec)
+	sqi.SetFloat64(1 / math.Sqrt(xf))
+	for prec := z.prec + 32; sqi.prec < prec; {
+		sqi.prec *= 2
+		sqi = ng(sqi)
+	}
+	// sqi = 1/√x
+
+	// x/√x = √x
+	z.Mul(x, sqi)
+}
+
+// newFloat returns a new *Float with space for twice the given
+// precision.
+func newFloat(prec2 uint32) *Float {
+	z := new(Float)
+	// nat.make ensures the slice length is > 0
+	z.mant = z.mant.make(int(prec2/_W) * 2)
+	return z
+}
diff --git a/contrib/go/_std_1.18/src/math/bits.go b/contrib/go/_std_1.18/src/math/bits.go
new file mode 100644
index 0000000000..77bcdbe1ce
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/bits.go
@@ -0,0 +1,62 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+const (
+	uvnan    = 0x7FF8000000000001
+	uvinf    = 0x7FF0000000000000
+	uvneginf = 0xFFF0000000000000
+	uvone    = 0x3FF0000000000000
+	mask     = 0x7FF
+	shift    = 64 - 11 - 1
+	bias     = 1023
+	signMask = 1 << 63
+	fracMask = 1<<shift - 1
+)
+
+// Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.
+func Inf(sign int) float64 {
+	var v uint64
+	if sign >= 0 {
+		v = uvinf
+	} else {
+		v = uvneginf
+	}
+	return Float64frombits(v)
+}
+
+// NaN returns an IEEE 754 ``not-a-number'' value.
+func NaN() float64 { return Float64frombits(uvnan) }
+
+// IsNaN reports whether f is an IEEE 754 ``not-a-number'' value.
+func IsNaN(f float64) (is bool) {
+	// IEEE 754 says that only NaNs satisfy f != f.
+	// To avoid the floating-point hardware, could use:
+	//	x := Float64bits(f);
+	//	return uint32(x>>shift)&mask == mask && x != uvinf && x != uvneginf
+	return f != f
+}
+
+// IsInf reports whether f is an infinity, according to sign.
+// If sign > 0, IsInf reports whether f is positive infinity.
+// If sign < 0, IsInf reports whether f is negative infinity.
+// If sign == 0, IsInf reports whether f is either infinity.
+func IsInf(f float64, sign int) bool {
+	// Test for infinity by comparing against maximum float.
+	// To avoid the floating-point hardware, could use:
+	//	x := Float64bits(f);
+	//	return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf;
+	return sign >= 0 && f > MaxFloat64 || sign <= 0 && f < -MaxFloat64
+}
+
+// normalize returns a normal number y and exponent exp
+// satisfying x == y × 2**exp. It assumes x is finite and non-zero.
+func normalize(x float64) (y float64, exp int) {
+	const SmallestNormal = 2.2250738585072014e-308 // 2**-1022
+	if Abs(x) < SmallestNormal {
+		return x * (1 << 52), -52
+	}
+	return x, 0
+}
diff --git a/contrib/go/_std_1.18/src/math/bits/bits.go b/contrib/go/_std_1.18/src/math/bits/bits.go
new file mode 100644
index 0000000000..65452feda2
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/bits/bits.go
@@ -0,0 +1,588 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate go run make_tables.go
+
+// Package bits implements bit counting and manipulation
+// functions for the predeclared unsigned integer types.
+package bits
+
+const uintSize = 32 << (^uint(0) >> 63) // 32 or 64
+
+// UintSize is the size of a uint in bits.
+const UintSize = uintSize
+
+// --- LeadingZeros ---
+
+// LeadingZeros returns the number of leading zero bits in x; the result is UintSize for x == 0.
+func LeadingZeros(x uint) int { return UintSize - Len(x) }
+
+// LeadingZeros8 returns the number of leading zero bits in x; the result is 8 for x == 0.
+func LeadingZeros8(x uint8) int { return 8 - Len8(x) }
+
+// LeadingZeros16 returns the number of leading zero bits in x; the result is 16 for x == 0.
+func LeadingZeros16(x uint16) int { return 16 - Len16(x) }
+
+// LeadingZeros32 returns the number of leading zero bits in x; the result is 32 for x == 0.
+func LeadingZeros32(x uint32) int { return 32 - Len32(x) }
+
+// LeadingZeros64 returns the number of leading zero bits in x; the result is 64 for x == 0.
+func LeadingZeros64(x uint64) int { return 64 - Len64(x) }
+
+// --- TrailingZeros ---
+
+// See http://supertech.csail.mit.edu/papers/debruijn.pdf
+const deBruijn32 = 0x077CB531
+
+var deBruijn32tab = [32]byte{
+	0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8,
+	31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9,
+}
+
+const deBruijn64 = 0x03f79d71b4ca8b09
+
+var deBruijn64tab = [64]byte{
+	0, 1, 56, 2, 57, 49, 28, 3, 61, 58, 42, 50, 38, 29, 17, 4,
+	62, 47, 59, 36, 45, 43, 51, 22, 53, 39, 33, 30, 24, 18, 12, 5,
+	63, 55, 48, 27, 60, 41, 37, 16, 46, 35, 44, 21, 52, 32, 23, 11,
+	54, 26, 40, 15, 34, 20, 31, 10, 25, 14, 19, 9, 13, 8, 7, 6,
+}
+
+// TrailingZeros returns the number of trailing zero bits in x; the result is UintSize for x == 0.
+func TrailingZeros(x uint) int {
+	if UintSize == 32 {
+		return TrailingZeros32(uint32(x))
+	}
+	return TrailingZeros64(uint64(x))
+}
+
+// TrailingZeros8 returns the number of trailing zero bits in x; the result is 8 for x == 0.
+func TrailingZeros8(x uint8) int {
+	return int(ntz8tab[x])
+}
+
+// TrailingZeros16 returns the number of trailing zero bits in x; the result is 16 for x == 0.
+func TrailingZeros16(x uint16) int {
+	if x == 0 {
+		return 16
+	}
+	// see comment in TrailingZeros64
+	return int(deBruijn32tab[uint32(x&-x)*deBruijn32>>(32-5)])
+}
+
+// TrailingZeros32 returns the number of trailing zero bits in x; the result is 32 for x == 0.
+func TrailingZeros32(x uint32) int {
+	if x == 0 {
+		return 32
+	}
+	// see comment in TrailingZeros64
+	return int(deBruijn32tab[(x&-x)*deBruijn32>>(32-5)])
+}
+
+// TrailingZeros64 returns the number of trailing zero bits in x; the result is 64 for x == 0.
+func TrailingZeros64(x uint64) int {
+	if x == 0 {
+		return 64
+	}
+	// If popcount is fast, replace code below with return popcount(^x & (x - 1)).
+	//
+	// x & -x leaves only the right-most bit set in the word. Let k be the
+	// index of that bit. Since only a single bit is set, the value is two
+	// to the power of k. Multiplying by a power of two is equivalent to
+	// left shifting, in this case by k bits. The de Bruijn (64 bit) constant
+	// is such that all six bit, consecutive substrings are distinct.
+	// Therefore, if we have a left shifted version of this constant we can
+	// find by how many bits it was shifted by looking at which six bit
+	// substring ended up at the top of the word.
+	// (Knuth, volume 4, section 7.3.1)
+	return int(deBruijn64tab[(x&-x)*deBruijn64>>(64-6)])
+}
+
+// --- OnesCount ---
+
+const m0 = 0x5555555555555555 // 01010101 ...
+const m1 = 0x3333333333333333 // 00110011 ...
+const m2 = 0x0f0f0f0f0f0f0f0f // 00001111 ...
+const m3 = 0x00ff00ff00ff00ff // etc.
+const m4 = 0x0000ffff0000ffff
+
+// OnesCount returns the number of one bits ("population count") in x.
+func OnesCount(x uint) int {
+	if UintSize == 32 {
+		return OnesCount32(uint32(x))
+	}
+	return OnesCount64(uint64(x))
+}
+
+// OnesCount8 returns the number of one bits ("population count") in x.
+func OnesCount8(x uint8) int {
+	return int(pop8tab[x])
+}
+
+// OnesCount16 returns the number of one bits ("population count") in x.
+func OnesCount16(x uint16) int {
+	return int(pop8tab[x>>8] + pop8tab[x&0xff])
+}
+
+// OnesCount32 returns the number of one bits ("population count") in x.
+func OnesCount32(x uint32) int {
+	return int(pop8tab[x>>24] + pop8tab[x>>16&0xff] + pop8tab[x>>8&0xff] + pop8tab[x&0xff])
+}
+
+// OnesCount64 returns the number of one bits ("population count") in x.
+func OnesCount64(x uint64) int {
+	// Implementation: Parallel summing of adjacent bits.
+	// See "Hacker's Delight", Chap. 5: Counting Bits.
+	// The following pattern shows the general approach:
+	//
+	//   x = x>>1&(m0&m) + x&(m0&m)
+	//   x = x>>2&(m1&m) + x&(m1&m)
+	//   x = x>>4&(m2&m) + x&(m2&m)
+	//   x = x>>8&(m3&m) + x&(m3&m)
+	//   x = x>>16&(m4&m) + x&(m4&m)
+	//   x = x>>32&(m5&m) + x&(m5&m)
+	//   return int(x)
+	//
+	// Masking (& operations) can be left away when there's no
+	// danger that a field's sum will carry over into the next
+	// field: Since the result cannot be > 64, 8 bits is enough
+	// and we can ignore the masks for the shifts by 8 and up.
+	// Per "Hacker's Delight", the first line can be simplified
+	// more, but it saves at best one instruction, so we leave
+	// it alone for clarity.
+	const m = 1<<64 - 1
+	x = x>>1&(m0&m) + x&(m0&m)
+	x = x>>2&(m1&m) + x&(m1&m)
+	x = (x>>4 + x) & (m2 & m)
+	x += x >> 8
+	x += x >> 16
+	x += x >> 32
+	return int(x) & (1<<7 - 1)
+}
+
+// --- RotateLeft ---
+
+// RotateLeft returns the value of x rotated left by (k mod UintSize) bits.
+// To rotate x right by k bits, call RotateLeft(x, -k).
+//
+// This function's execution time does not depend on the inputs.
+func RotateLeft(x uint, k int) uint {
+	if UintSize == 32 {
+		return uint(RotateLeft32(uint32(x), k))
+	}
+	return uint(RotateLeft64(uint64(x), k))
+}
+
+// RotateLeft8 returns the value of x rotated left by (k mod 8) bits.
+// To rotate x right by k bits, call RotateLeft8(x, -k).
+//
+// This function's execution time does not depend on the inputs.
+func RotateLeft8(x uint8, k int) uint8 {
+	const n = 8
+	s := uint(k) & (n - 1)
+	return x<<s | x>>(n-s)
+}
+
+// RotateLeft16 returns the value of x rotated left by (k mod 16) bits.
+// To rotate x right by k bits, call RotateLeft16(x, -k).
+//
+// This function's execution time does not depend on the inputs.
+func RotateLeft16(x uint16, k int) uint16 {
+	const n = 16
+	s := uint(k) & (n - 1)
+	return x<<s | x>>(n-s)
+}
+
+// RotateLeft32 returns the value of x rotated left by (k mod 32) bits.
+// To rotate x right by k bits, call RotateLeft32(x, -k).
+//
+// This function's execution time does not depend on the inputs.
+func RotateLeft32(x uint32, k int) uint32 {
+	const n = 32
+	s := uint(k) & (n - 1)
+	return x<<s | x>>(n-s)
+}
+
+// RotateLeft64 returns the value of x rotated left by (k mod 64) bits.
+// To rotate x right by k bits, call RotateLeft64(x, -k).
+//
+// This function's execution time does not depend on the inputs.
+func RotateLeft64(x uint64, k int) uint64 {
+	const n = 64
+	s := uint(k) & (n - 1)
+	return x<<s | x>>(n-s)
+}
+
+// --- Reverse ---
+
+// Reverse returns the value of x with its bits in reversed order.
+func Reverse(x uint) uint {
+	if UintSize == 32 {
+		return uint(Reverse32(uint32(x)))
+	}
+	return uint(Reverse64(uint64(x)))
+}
+
+// Reverse8 returns the value of x with its bits in reversed order.
+func Reverse8(x uint8) uint8 {
+	return rev8tab[x]
+}
+
+// Reverse16 returns the value of x with its bits in reversed order.
+func Reverse16(x uint16) uint16 {
+	return uint16(rev8tab[x>>8]) | uint16(rev8tab[x&0xff])<<8
+}
+
+// Reverse32 returns the value of x with its bits in reversed order.
+func Reverse32(x uint32) uint32 {
+	const m = 1<<32 - 1
+	x = x>>1&(m0&m) | x&(m0&m)<<1
+	x = x>>2&(m1&m) | x&(m1&m)<<2
+	x = x>>4&(m2&m) | x&(m2&m)<<4
+	return ReverseBytes32(x)
+}
+
+// Reverse64 returns the value of x with its bits in reversed order.
+func Reverse64(x uint64) uint64 {
+	const m = 1<<64 - 1
+	x = x>>1&(m0&m) | x&(m0&m)<<1
+	x = x>>2&(m1&m) | x&(m1&m)<<2
+	x = x>>4&(m2&m) | x&(m2&m)<<4
+	return ReverseBytes64(x)
+}
+
+// --- ReverseBytes ---
+
+// ReverseBytes returns the value of x with its bytes in reversed order.
+//
+// This function's execution time does not depend on the inputs.
+func ReverseBytes(x uint) uint {
+	if UintSize == 32 {
+		return uint(ReverseBytes32(uint32(x)))
+	}
+	return uint(ReverseBytes64(uint64(x)))
+}
+
+// ReverseBytes16 returns the value of x with its bytes in reversed order.
+//
+// This function's execution time does not depend on the inputs.
+func ReverseBytes16(x uint16) uint16 {
+	return x>>8 | x<<8
+}
+
+// ReverseBytes32 returns the value of x with its bytes in reversed order.
+//
+// This function's execution time does not depend on the inputs.
+func ReverseBytes32(x uint32) uint32 {
+	const m = 1<<32 - 1
+	x = x>>8&(m3&m) | x&(m3&m)<<8
+	return x>>16 | x<<16
+}
+
+// ReverseBytes64 returns the value of x with its bytes in reversed order.
+//
+// This function's execution time does not depend on the inputs.
+func ReverseBytes64(x uint64) uint64 {
+	const m = 1<<64 - 1
+	x = x>>8&(m3&m) | x&(m3&m)<<8
+	x = x>>16&(m4&m) | x&(m4&m)<<16
+	return x>>32 | x<<32
+}
+
+// --- Len ---
+
+// Len returns the minimum number of bits required to represent x; the result is 0 for x == 0.
+func Len(x uint) int {
+	if UintSize == 32 {
+		return Len32(uint32(x))
+	}
+	return Len64(uint64(x))
+}
+
+// Len8 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
+func Len8(x uint8) int {
+	return int(len8tab[x])
+}
+
+// Len16 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
+func Len16(x uint16) (n int) {
+	if x >= 1<<8 {
+		x >>= 8
+		n = 8
+	}
+	return n + int(len8tab[x])
+}
+
+// Len32 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
+func Len32(x uint32) (n int) {
+	if x >= 1<<16 {
+		x >>= 16
+		n = 16
+	}
+	if x >= 1<<8 {
+		x >>= 8
+		n += 8
+	}
+	return n + int(len8tab[x])
+}
+
+// Len64 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
+func Len64(x uint64) (n int) {
+	if x >= 1<<32 {
+		x >>= 32
+		n = 32
+	}
+	if x >= 1<<16 {
+		x >>= 16
+		n += 16
+	}
+	if x >= 1<<8 {
+		x >>= 8
+		n += 8
+	}
+	return n + int(len8tab[x])
+}
+
+// --- Add with carry ---
+
+// Add returns the sum with carry of x, y and carry: sum = x + y + carry.
+// The carry input must be 0 or 1; otherwise the behavior is undefined.
+// The carryOut output is guaranteed to be 0 or 1.
+//
+// This function's execution time does not depend on the inputs.
+func Add(x, y, carry uint) (sum, carryOut uint) {
+	if UintSize == 32 {
+		s32, c32 := Add32(uint32(x), uint32(y), uint32(carry))
+		return uint(s32), uint(c32)
+	}
+	s64, c64 := Add64(uint64(x), uint64(y), uint64(carry))
+	return uint(s64), uint(c64)
+}
+
+// Add32 returns the sum with carry of x, y and carry: sum = x + y + carry.
+// The carry input must be 0 or 1; otherwise the behavior is undefined.
+// The carryOut output is guaranteed to be 0 or 1.
+//
+// This function's execution time does not depend on the inputs.
+func Add32(x, y, carry uint32) (sum, carryOut uint32) {
+	sum64 := uint64(x) + uint64(y) + uint64(carry)
+	sum = uint32(sum64)
+	carryOut = uint32(sum64 >> 32)
+	return
+}
+
+// Add64 returns the sum with carry of x, y and carry: sum = x + y + carry.
+// The carry input must be 0 or 1; otherwise the behavior is undefined.
+// The carryOut output is guaranteed to be 0 or 1.
+//
+// This function's execution time does not depend on the inputs.
+func Add64(x, y, carry uint64) (sum, carryOut uint64) {
+	sum = x + y + carry
+	// The sum will overflow if both top bits are set (x & y) or if one of them
+	// is (x | y), and a carry from the lower place happened. If such a carry
+	// happens, the top bit will be 1 + 0 + 1 = 0 (&^ sum).
+	carryOut = ((x & y) | ((x | y) &^ sum)) >> 63
+	return
+}
+
+// --- Subtract with borrow ---
+
+// Sub returns the difference of x, y and borrow: diff = x - y - borrow.
+// The borrow input must be 0 or 1; otherwise the behavior is undefined.
+// The borrowOut output is guaranteed to be 0 or 1.
+//
+// This function's execution time does not depend on the inputs.
+func Sub(x, y, borrow uint) (diff, borrowOut uint) {
+	if UintSize == 32 {
+		d32, b32 := Sub32(uint32(x), uint32(y), uint32(borrow))
+		return uint(d32), uint(b32)
+	}
+	d64, b64 := Sub64(uint64(x), uint64(y), uint64(borrow))
+	return uint(d64), uint(b64)
+}
+
+// Sub32 returns the difference of x, y and borrow, diff = x - y - borrow.
+// The borrow input must be 0 or 1; otherwise the behavior is undefined.
+// The borrowOut output is guaranteed to be 0 or 1.
+//
+// This function's execution time does not depend on the inputs.
+func Sub32(x, y, borrow uint32) (diff, borrowOut uint32) {
+	diff = x - y - borrow
+	// The difference will underflow if the top bit of x is not set and the top
+	// bit of y is set (^x & y) or if they are the same (^(x ^ y)) and a borrow
+	// from the lower place happens. If that borrow happens, the result will be
+	// 1 - 1 - 1 = 0 - 0 - 1 = 1 (& diff).
+	borrowOut = ((^x & y) | (^(x ^ y) & diff)) >> 31
+	return
+}
+
+// Sub64 returns the difference of x, y and borrow: diff = x - y - borrow.
+// The borrow input must be 0 or 1; otherwise the behavior is undefined.
+// The borrowOut output is guaranteed to be 0 or 1.
+//
+// This function's execution time does not depend on the inputs.
+func Sub64(x, y, borrow uint64) (diff, borrowOut uint64) {
+	diff = x - y - borrow
+	// See Sub32 for the bit logic.
+	borrowOut = ((^x & y) | (^(x ^ y) & diff)) >> 63
+	return
+}
+
+// --- Full-width multiply ---
+
+// Mul returns the full-width product of x and y: (hi, lo) = x * y
+// with the product bits' upper half returned in hi and the lower
+// half returned in lo.
+//
+// This function's execution time does not depend on the inputs.
+func Mul(x, y uint) (hi, lo uint) {
+	if UintSize == 32 {
+		h, l := Mul32(uint32(x), uint32(y))
+		return uint(h), uint(l)
+	}
+	h, l := Mul64(uint64(x), uint64(y))
+	return uint(h), uint(l)
+}
+
+// Mul32 returns the 64-bit product of x and y: (hi, lo) = x * y
+// with the product bits' upper half returned in hi and the lower
+// half returned in lo.
+//
+// This function's execution time does not depend on the inputs.
+func Mul32(x, y uint32) (hi, lo uint32) {
+	tmp := uint64(x) * uint64(y)
+	hi, lo = uint32(tmp>>32), uint32(tmp)
+	return
+}
+
+// Mul64 returns the 128-bit product of x and y: (hi, lo) = x * y
+// with the product bits' upper half returned in hi and the lower
+// half returned in lo.
+//
+// This function's execution time does not depend on the inputs.
+func Mul64(x, y uint64) (hi, lo uint64) {
+	const mask32 = 1<<32 - 1
+	x0 := x & mask32
+	x1 := x >> 32
+	y0 := y & mask32
+	y1 := y >> 32
+	w0 := x0 * y0
+	t := x1*y0 + w0>>32
+	w1 := t & mask32
+	w2 := t >> 32
+	w1 += x0 * y1
+	hi = x1*y1 + w2 + w1>>32
+	lo = x * y
+	return
+}
+
+// --- Full-width divide ---
+
+// Div returns the quotient and remainder of (hi, lo) divided by y:
+// quo = (hi, lo)/y, rem = (hi, lo)%y with the dividend bits' upper
+// half in parameter hi and the lower half in parameter lo.
+// Div panics for y == 0 (division by zero) or y <= hi (quotient overflow).
+func Div(hi, lo, y uint) (quo, rem uint) {
+	if UintSize == 32 {
+		q, r := Div32(uint32(hi), uint32(lo), uint32(y))
+		return uint(q), uint(r)
+	}
+	q, r := Div64(uint64(hi), uint64(lo), uint64(y))
+	return uint(q), uint(r)
+}
+
+// Div32 returns the quotient and remainder of (hi, lo) divided by y:
+// quo = (hi, lo)/y, rem = (hi, lo)%y with the dividend bits' upper
+// half in parameter hi and the lower half in parameter lo.
+// Div32 panics for y == 0 (division by zero) or y <= hi (quotient overflow).
+func Div32(hi, lo, y uint32) (quo, rem uint32) {
+	if y != 0 && y <= hi {
+		panic(overflowError)
+	}
+	z := uint64(hi)<<32 | uint64(lo)
+	quo, rem = uint32(z/uint64(y)), uint32(z%uint64(y))
+	return
+}
+
+// Div64 returns the quotient and remainder of (hi, lo) divided by y:
+// quo = (hi, lo)/y, rem = (hi, lo)%y with the dividend bits' upper
+// half in parameter hi and the lower half in parameter lo.
+// Div64 panics for y == 0 (division by zero) or y <= hi (quotient overflow).
+func Div64(hi, lo, y uint64) (quo, rem uint64) {
+	const (
+		two32  = 1 << 32
+		mask32 = two32 - 1
+	)
+	if y == 0 {
+		panic(divideError)
+	}
+	if y <= hi {
+		panic(overflowError)
+	}
+
+	s := uint(LeadingZeros64(y))
+	y <<= s
+
+	yn1 := y >> 32
+	yn0 := y & mask32
+	un32 := hi<<s | lo>>(64-s)
+	un10 := lo << s
+	un1 := un10 >> 32
+	un0 := un10 & mask32
+	q1 := un32 / yn1
+	rhat := un32 - q1*yn1
+
+	for q1 >= two32 || q1*yn0 > two32*rhat+un1 {
+		q1--
+		rhat += yn1
+		if rhat >= two32 {
+			break
+		}
+	}
+
+	un21 := un32*two32 + un1 - q1*y
+	q0 := un21 / yn1
+	rhat = un21 - q0*yn1
+
+	for q0 >= two32 || q0*yn0 > two32*rhat+un0 {
+		q0--
+		rhat += yn1
+		if rhat >= two32 {
+			break
+		}
+	}
+
+	return q1*two32 + q0, (un21*two32 + un0 - q0*y) >> s
+}
+
+// Rem returns the remainder of (hi, lo) divided by y. Rem panics for
+// y == 0 (division by zero) but, unlike Div, it doesn't panic on a
+// quotient overflow.
+func Rem(hi, lo, y uint) uint {
+	if UintSize == 32 {
+		return uint(Rem32(uint32(hi), uint32(lo), uint32(y)))
+	}
+	return uint(Rem64(uint64(hi), uint64(lo), uint64(y)))
+}
+
+// Rem32 returns the remainder of (hi, lo) divided by y. Rem32 panics
+// for y == 0 (division by zero) but, unlike Div32, it doesn't panic
+// on a quotient overflow.
+func Rem32(hi, lo, y uint32) uint32 {
+	return uint32((uint64(hi)<<32 | uint64(lo)) % uint64(y))
+}
+
+// Rem64 returns the remainder of (hi, lo) divided by y. Rem64 panics
+// for y == 0 (division by zero) but, unlike Div64, it doesn't panic
+// on a quotient overflow.
+func Rem64(hi, lo, y uint64) uint64 {
+	// We scale down hi so that hi < y, then use Div64 to compute the
+	// rem with the guarantee that it won't panic on quotient overflow.
+	// Given that
+	//   hi ≡ hi%y    (mod y)
+	// we have
+	//   hi<<64 + lo ≡ (hi%y)<<64 + lo    (mod y)
+	_, rem := Div64(hi%y, lo, y)
+	return rem
+}
diff --git a/contrib/go/_std_1.18/src/math/bits/bits_errors.go b/contrib/go/_std_1.18/src/math/bits/bits_errors.go
new file mode 100644
index 0000000000..61cb5c9457
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/bits/bits_errors.go
@@ -0,0 +1,16 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !compiler_bootstrap
+// +build !compiler_bootstrap
+
+package bits
+
+import _ "unsafe"
+
+//go:linkname overflowError runtime.overflowError
+var overflowError error
+
+//go:linkname divideError runtime.divideError
+var divideError error
diff --git a/contrib/go/_std_1.18/src/math/bits/bits_tables.go b/contrib/go/_std_1.18/src/math/bits/bits_tables.go
new file mode 100644
index 0000000000..f869b8d5c3
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/bits/bits_tables.go
@@ -0,0 +1,79 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated by go run make_tables.go. DO NOT EDIT.
+
+package bits
+
+const ntz8tab = "" +
+	"\x08\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x05\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x06\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x05\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x07\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x05\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x06\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x05\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
+	"\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00"
+
+const pop8tab = "" +
+	"\x00\x01\x01\x02\x01\x02\x02\x03\x01\x02\x02\x03\x02\x03\x03\x04" +
+	"\x01\x02\x02\x03\x02\x03\x03\x04\x02\x03\x03\x04\x03\x04\x04\x05" +
+	"\x01\x02\x02\x03\x02\x03\x03\x04\x02\x03\x03\x04\x03\x04\x04\x05" +
+	"\x02\x03\x03\x04\x03\x04\x04\x05\x03\x04\x04\x05\x04\x05\x05\x06" +
+	"\x01\x02\x02\x03\x02\x03\x03\x04\x02\x03\x03\x04\x03\x04\x04\x05" +
+	"\x02\x03\x03\x04\x03\x04\x04\x05\x03\x04\x04\x05\x04\x05\x05\x06" +
+	"\x02\x03\x03\x04\x03\x04\x04\x05\x03\x04\x04\x05\x04\x05\x05\x06" +
+	"\x03\x04\x04\x05\x04\x05\x05\x06\x04\x05\x05\x06\x05\x06\x06\x07" +
+	"\x01\x02\x02\x03\x02\x03\x03\x04\x02\x03\x03\x04\x03\x04\x04\x05" +
+	"\x02\x03\x03\x04\x03\x04\x04\x05\x03\x04\x04\x05\x04\x05\x05\x06" +
+	"\x02\x03\x03\x04\x03\x04\x04\x05\x03\x04\x04\x05\x04\x05\x05\x06" +
+	"\x03\x04\x04\x05\x04\x05\x05\x06\x04\x05\x05\x06\x05\x06\x06\x07" +
+	"\x02\x03\x03\x04\x03\x04\x04\x05\x03\x04\x04\x05\x04\x05\x05\x06" +
+	"\x03\x04\x04\x05\x04\x05\x05\x06\x04\x05\x05\x06\x05\x06\x06\x07" +
+	"\x03\x04\x04\x05\x04\x05\x05\x06\x04\x05\x05\x06\x05\x06\x06\x07" +
+	"\x04\x05\x05\x06\x05\x06\x06\x07\x05\x06\x06\x07\x06\x07\x07\x08"
+
+const rev8tab = "" +
+	"\x00\x80\x40\xc0\x20\xa0\x60\xe0\x10\x90\x50\xd0\x30\xb0\x70\xf0" +
+	"\x08\x88\x48\xc8\x28\xa8\x68\xe8\x18\x98\x58\xd8\x38\xb8\x78\xf8" +
+	"\x04\x84\x44\xc4\x24\xa4\x64\xe4\x14\x94\x54\xd4\x34\xb4\x74\xf4" +
+	"\x0c\x8c\x4c\xcc\x2c\xac\x6c\xec\x1c\x9c\x5c\xdc\x3c\xbc\x7c\xfc" +
+	"\x02\x82\x42\xc2\x22\xa2\x62\xe2\x12\x92\x52\xd2\x32\xb2\x72\xf2" +
+	"\x0a\x8a\x4a\xca\x2a\xaa\x6a\xea\x1a\x9a\x5a\xda\x3a\xba\x7a\xfa" +
+	"\x06\x86\x46\xc6\x26\xa6\x66\xe6\x16\x96\x56\xd6\x36\xb6\x76\xf6" +
+	"\x0e\x8e\x4e\xce\x2e\xae\x6e\xee\x1e\x9e\x5e\xde\x3e\xbe\x7e\xfe" +
+	"\x01\x81\x41\xc1\x21\xa1\x61\xe1\x11\x91\x51\xd1\x31\xb1\x71\xf1" +
+	"\x09\x89\x49\xc9\x29\xa9\x69\xe9\x19\x99\x59\xd9\x39\xb9\x79\xf9" +
+	"\x05\x85\x45\xc5\x25\xa5\x65\xe5\x15\x95\x55\xd5\x35\xb5\x75\xf5" +
+	"\x0d\x8d\x4d\xcd\x2d\xad\x6d\xed\x1d\x9d\x5d\xdd\x3d\xbd\x7d\xfd" +
+	"\x03\x83\x43\xc3\x23\xa3\x63\xe3\x13\x93\x53\xd3\x33\xb3\x73\xf3" +
+	"\x0b\x8b\x4b\xcb\x2b\xab\x6b\xeb\x1b\x9b\x5b\xdb\x3b\xbb\x7b\xfb" +
+	"\x07\x87\x47\xc7\x27\xa7\x67\xe7\x17\x97\x57\xd7\x37\xb7\x77\xf7" +
+	"\x0f\x8f\x4f\xcf\x2f\xaf\x6f\xef\x1f\x9f\x5f\xdf\x3f\xbf\x7f\xff"
+
+const len8tab = "" +
+	"\x00\x01\x02\x02\x03\x03\x03\x03\x04\x04\x04\x04\x04\x04\x04\x04" +
+	"\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05" +
+	"\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06" +
+	"\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06\x06" +
+	"\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07" +
+	"\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07" +
+	"\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07" +
+	"\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07\x07" +
+	"\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+	"\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+	"\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+	"\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+	"\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+	"\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+	"\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08" +
+	"\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08\x08"
diff --git a/contrib/go/_std_1.18/src/math/cbrt.go b/contrib/go/_std_1.18/src/math/cbrt.go
new file mode 100644
index 0000000000..45c8ecb3a8
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/cbrt.go
@@ -0,0 +1,84 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// The go code is a modified version of the original C code from
+// http://www.netlib.org/fdlibm/s_cbrt.c and came with this notice.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunSoft, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+
+// Cbrt returns the cube root of x.
+//
+// Special cases are:
+//	Cbrt(±0) = ±0
+//	Cbrt(±Inf) = ±Inf
+//	Cbrt(NaN) = NaN
+func Cbrt(x float64) float64 {
+	if haveArchCbrt {
+		return archCbrt(x)
+	}
+	return cbrt(x)
+}
+
+func cbrt(x float64) float64 {
+	const (
+		B1             = 715094163                   // (682-0.03306235651)*2**20
+		B2             = 696219795                   // (664-0.03306235651)*2**20
+		C              = 5.42857142857142815906e-01  // 19/35     = 0x3FE15F15F15F15F1
+		D              = -7.05306122448979611050e-01 // -864/1225 = 0xBFE691DE2532C834
+		E              = 1.41428571428571436819e+00  // 99/70     = 0x3FF6A0EA0EA0EA0F
+		F              = 1.60714285714285720630e+00  // 45/28     = 0x3FF9B6DB6DB6DB6E
+		G              = 3.57142857142857150787e-01  // 5/14      = 0x3FD6DB6DB6DB6DB7
+		SmallestNormal = 2.22507385850720138309e-308 // 2**-1022  = 0x0010000000000000
+	)
+	// special cases
+	switch {
+	case x == 0 || IsNaN(x) || IsInf(x, 0):
+		return x
+	}
+
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+
+	// rough cbrt to 5 bits
+	t := Float64frombits(Float64bits(x)/3 + B1<<32)
+	if x < SmallestNormal {
+		// subnormal number
+		t = float64(1 << 54) // set t= 2**54
+		t *= x
+		t = Float64frombits(Float64bits(t)/3 + B2<<32)
+	}
+
+	// new cbrt to 23 bits
+	r := t * t / x
+	s := C + r*t
+	t *= G + F/(s+E+D/s)
+
+	// chop to 22 bits, make larger than cbrt(x)
+	t = Float64frombits(Float64bits(t)&(0xFFFFFFFFC<<28) + 1<<30)
+
+	// one step newton iteration to 53 bits with error less than 0.667ulps
+	s = t * t // t*t is exact
+	r = x / s
+	w := t + t
+	r = (r - t) / (w + r) // r-s is exact
+	t = t + t*r
+
+	// restore the sign bit
+	if sign {
+		t = -t
+	}
+	return t
+}
diff --git a/contrib/go/_std_1.18/src/math/const.go b/contrib/go/_std_1.18/src/math/const.go
new file mode 100644
index 0000000000..5ea935fb42
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/const.go
@@ -0,0 +1,57 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package math provides basic constants and mathematical functions.
+//
+// This package does not guarantee bit-identical results across architectures.
+package math
+
+// Mathematical constants.
+const (
+	E   = 2.71828182845904523536028747135266249775724709369995957496696763 // https://oeis.org/A001113
+	Pi  = 3.14159265358979323846264338327950288419716939937510582097494459 // https://oeis.org/A000796
+	Phi = 1.61803398874989484820458683436563811772030917980576286213544862 // https://oeis.org/A001622
+
+	Sqrt2   = 1.41421356237309504880168872420969807856967187537694807317667974 // https://oeis.org/A002193
+	SqrtE   = 1.64872127070012814684865078781416357165377610071014801157507931 // https://oeis.org/A019774
+	SqrtPi  = 1.77245385090551602729816748334114518279754945612238712821380779 // https://oeis.org/A002161
+	SqrtPhi = 1.27201964951406896425242246173749149171560804184009624861664038 // https://oeis.org/A139339
+
+	Ln2    = 0.693147180559945309417232121458176568075500134360255254120680009 // https://oeis.org/A002162
+	Log2E  = 1 / Ln2
+	Ln10   = 2.30258509299404568401799145468436420760110148862877297603332790 // https://oeis.org/A002392
+	Log10E = 1 / Ln10
+)
+
+// Floating-point limit values.
+// Max is the largest finite value representable by the type.
+// SmallestNonzero is the smallest positive, non-zero value representable by the type.
+const (
+	MaxFloat32             = 0x1p127 * (1 + (1 - 0x1p-23)) // 3.40282346638528859811704183484516925440e+38
+	SmallestNonzeroFloat32 = 0x1p-126 * 0x1p-23            // 1.401298464324817070923729583289916131280e-45
+
+	MaxFloat64             = 0x1p1023 * (1 + (1 - 0x1p-52)) // 1.79769313486231570814527423731704356798070e+308
+	SmallestNonzeroFloat64 = 0x1p-1022 * 0x1p-52            // 4.9406564584124654417656879286822137236505980e-324
+)
+
+// Integer limit values.
+const (
+	intSize = 32 << (^uint(0) >> 63) // 32 or 64
+
+	MaxInt    = 1<<(intSize-1) - 1
+	MinInt    = -1 << (intSize - 1)
+	MaxInt8   = 1<<7 - 1
+	MinInt8   = -1 << 7
+	MaxInt16  = 1<<15 - 1
+	MinInt16  = -1 << 15
+	MaxInt32  = 1<<31 - 1
+	MinInt32  = -1 << 31
+	MaxInt64  = 1<<63 - 1
+	MinInt64  = -1 << 63
+	MaxUint   = 1<<intSize - 1
+	MaxUint8  = 1<<8 - 1
+	MaxUint16 = 1<<16 - 1
+	MaxUint32 = 1<<32 - 1
+	MaxUint64 = 1<<64 - 1
+)
diff --git a/contrib/go/_std_1.18/src/math/copysign.go b/contrib/go/_std_1.18/src/math/copysign.go
new file mode 100644
index 0000000000..719c64b9eb
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/copysign.go
@@ -0,0 +1,12 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Copysign returns a value with the magnitude
+// of x and the sign of y.
+func Copysign(x, y float64) float64 {
+	const sign = 1 << 63
+	return Float64frombits(Float64bits(x)&^sign | Float64bits(y)&sign)
+}
diff --git a/contrib/go/_std_1.18/src/math/dim.go b/contrib/go/_std_1.18/src/math/dim.go
new file mode 100644
index 0000000000..6a857bbe41
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/dim.go
@@ -0,0 +1,91 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Dim returns the maximum of x-y or 0.
+//
+// Special cases are:
+//	Dim(+Inf, +Inf) = NaN
+//	Dim(-Inf, -Inf) = NaN
+//	Dim(x, NaN) = Dim(NaN, x) = NaN
+func Dim(x, y float64) float64 {
+	// The special cases result in NaN after the subtraction:
+	//      +Inf - +Inf = NaN
+	//      -Inf - -Inf = NaN
+	//       NaN - y    = NaN
+	//         x - NaN  = NaN
+	v := x - y
+	if v <= 0 {
+		// v is negative or 0
+		return 0
+	}
+	// v is positive or NaN
+	return v
+}
+
+// Max returns the larger of x or y.
+//
+// Special cases are:
+//	Max(x, +Inf) = Max(+Inf, x) = +Inf
+//	Max(x, NaN) = Max(NaN, x) = NaN
+//	Max(+0, ±0) = Max(±0, +0) = +0
+//	Max(-0, -0) = -0
+func Max(x, y float64) float64 {
+	if haveArchMax {
+		return archMax(x, y)
+	}
+	return max(x, y)
+}
+
+func max(x, y float64) float64 {
+	// special cases
+	switch {
+	case IsInf(x, 1) || IsInf(y, 1):
+		return Inf(1)
+	case IsNaN(x) || IsNaN(y):
+		return NaN()
+	case x == 0 && x == y:
+		if Signbit(x) {
+			return y
+		}
+		return x
+	}
+	if x > y {
+		return x
+	}
+	return y
+}
+
+// Min returns the smaller of x or y.
+//
+// Special cases are:
+//	Min(x, -Inf) = Min(-Inf, x) = -Inf
+//	Min(x, NaN) = Min(NaN, x) = NaN
+//	Min(-0, ±0) = Min(±0, -0) = -0
+func Min(x, y float64) float64 {
+	if haveArchMin {
+		return archMin(x, y)
+	}
+	return min(x, y)
+}
+
+func min(x, y float64) float64 {
+	// special cases
+	switch {
+	case IsInf(x, -1) || IsInf(y, -1):
+		return Inf(-1)
+	case IsNaN(x) || IsNaN(y):
+		return NaN()
+	case x == 0 && x == y:
+		if Signbit(x) {
+			return x
+		}
+		return y
+	}
+	if x < y {
+		return x
+	}
+	return y
+}
diff --git a/contrib/go/_std_1.18/src/math/dim_amd64.s b/contrib/go/_std_1.18/src/math/dim_amd64.s
new file mode 100644
index 0000000000..253f03b97e
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/dim_amd64.s
@@ -0,0 +1,98 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "textflag.h"
+
+#define PosInf 0x7FF0000000000000
+#define NaN    0x7FF8000000000001
+#define NegInf 0xFFF0000000000000
+
+// func ·archMax(x, y float64) float64
+TEXT ·archMax(SB),NOSPLIT,$0
+	// +Inf special cases
+	MOVQ    $PosInf, AX
+	MOVQ    x+0(FP), R8
+	CMPQ    AX, R8
+	JEQ     isPosInf
+	MOVQ    y+8(FP), R9
+	CMPQ    AX, R9
+	JEQ     isPosInf
+	// NaN special cases
+	MOVQ    $~(1<<63), DX // bit mask
+	MOVQ    $PosInf, AX
+	MOVQ    R8, BX
+	ANDQ    DX, BX // x = |x|
+	CMPQ    AX, BX
+	JLT     isMaxNaN
+	MOVQ    R9, CX
+	ANDQ    DX, CX // y = |y|
+	CMPQ    AX, CX
+	JLT     isMaxNaN
+	// ±0 special cases
+	ORQ     CX, BX
+	JEQ     isMaxZero
+
+	MOVQ    R8, X0
+	MOVQ    R9, X1
+	MAXSD   X1, X0
+	MOVSD   X0, ret+16(FP)
+	RET
+isMaxNaN: // return NaN
+	MOVQ	$NaN, AX
+isPosInf: // return +Inf
+	MOVQ    AX, ret+16(FP)
+	RET
+isMaxZero:
+	MOVQ    $(1<<63), AX // -0.0
+	CMPQ    AX, R8
+	JEQ     +3(PC)
+	MOVQ    R8, ret+16(FP) // return 0
+	RET
+	MOVQ    R9, ret+16(FP) // return other 0
+	RET
+
+// func archMin(x, y float64) float64
+TEXT ·archMin(SB),NOSPLIT,$0
+	// -Inf special cases
+	MOVQ    $NegInf, AX
+	MOVQ    x+0(FP), R8
+	CMPQ    AX, R8
+	JEQ     isNegInf
+	MOVQ    y+8(FP), R9
+	CMPQ    AX, R9
+	JEQ     isNegInf
+	// NaN special cases
+	MOVQ    $~(1<<63), DX
+	MOVQ    $PosInf, AX
+	MOVQ    R8, BX
+	ANDQ    DX, BX // x = |x|
+	CMPQ    AX, BX
+	JLT     isMinNaN
+	MOVQ    R9, CX
+	ANDQ    DX, CX // y = |y|
+	CMPQ    AX, CX
+	JLT     isMinNaN
+	// ±0 special cases
+	ORQ     CX, BX
+	JEQ     isMinZero
+
+	MOVQ    R8, X0
+	MOVQ    R9, X1
+	MINSD   X1, X0
+	MOVSD X0, ret+16(FP)
+	RET
+isMinNaN: // return NaN
+	MOVQ	$NaN, AX
+isNegInf: // return -Inf
+	MOVQ    AX, ret+16(FP)
+	RET
+isMinZero:
+	MOVQ    $(1<<63), AX // -0.0
+	CMPQ    AX, R8
+	JEQ     +3(PC)
+	MOVQ    R9, ret+16(FP) // return other 0
+	RET
+	MOVQ    R8, ret+16(FP) // return -0
+	RET
+
diff --git a/contrib/go/_std_1.18/src/math/dim_asm.go b/contrib/go/_std_1.18/src/math/dim_asm.go
new file mode 100644
index 0000000000..f4adbd0ae5
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/dim_asm.go
@@ -0,0 +1,15 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build amd64 || arm64 || riscv64 || s390x
+
+package math
+
+const haveArchMax = true
+
+func archMax(x, y float64) float64
+
+const haveArchMin = true
+
+func archMin(x, y float64) float64
diff --git a/contrib/go/_std_1.18/src/math/erf.go b/contrib/go/_std_1.18/src/math/erf.go
new file mode 100644
index 0000000000..4d6fe472f1
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/erf.go
@@ -0,0 +1,349 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Floating-point error function and complementary error function.
+*/
+
+// The original C code and the long comment below are
+// from FreeBSD's /usr/src/lib/msun/src/s_erf.c and
+// came with this notice. The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+//
+// double erf(double x)
+// double erfc(double x)
+//                           x
+//                    2      |\
+//     erf(x)  =  ---------  | exp(-t*t)dt
+//                 sqrt(pi) \|
+//                           0
+//
+//     erfc(x) =  1-erf(x)
+//  Note that
+//              erf(-x) = -erf(x)
+//              erfc(-x) = 2 - erfc(x)
+//
+// Method:
+//      1. For |x| in [0, 0.84375]
+//          erf(x)  = x + x*R(x**2)
+//          erfc(x) = 1 - erf(x)           if x in [-.84375,0.25]
+//                  = 0.5 + ((0.5-x)-x*R)  if x in [0.25,0.84375]
+//         where R = P/Q where P is an odd poly of degree 8 and
+//         Q is an odd poly of degree 10.
+//                                               -57.90
+//                      | R - (erf(x)-x)/x | <= 2
+//
+//
+//         Remark. The formula is derived by noting
+//          erf(x) = (2/sqrt(pi))*(x - x**3/3 + x**5/10 - x**7/42 + ....)
+//         and that
+//          2/sqrt(pi) = 1.128379167095512573896158903121545171688
+//         is close to one. The interval is chosen because the fix
+//         point of erf(x) is near 0.6174 (i.e., erf(x)=x when x is
+//         near 0.6174), and by some experiment, 0.84375 is chosen to
+//         guarantee the error is less than one ulp for erf.
+//
+//      2. For |x| in [0.84375,1.25], let s = |x| - 1, and
+//         c = 0.84506291151 rounded to single (24 bits)
+//              erf(x)  = sign(x) * (c  + P1(s)/Q1(s))
+//              erfc(x) = (1-c)  - P1(s)/Q1(s) if x > 0
+//                        1+(c+P1(s)/Q1(s))    if x < 0
+//              |P1/Q1 - (erf(|x|)-c)| <= 2**-59.06
+//         Remark: here we use the taylor series expansion at x=1.
+//              erf(1+s) = erf(1) + s*Poly(s)
+//                       = 0.845.. + P1(s)/Q1(s)
+//         That is, we use rational approximation to approximate
+//                      erf(1+s) - (c = (single)0.84506291151)
+//         Note that |P1/Q1|< 0.078 for x in [0.84375,1.25]
+//         where
+//              P1(s) = degree 6 poly in s
+//              Q1(s) = degree 6 poly in s
+//
+//      3. For x in [1.25,1/0.35(~2.857143)],
+//              erfc(x) = (1/x)*exp(-x*x-0.5625+R1/S1)
+//              erf(x)  = 1 - erfc(x)
+//         where
+//              R1(z) = degree 7 poly in z, (z=1/x**2)
+//              S1(z) = degree 8 poly in z
+//
+//      4. For x in [1/0.35,28]
+//              erfc(x) = (1/x)*exp(-x*x-0.5625+R2/S2) if x > 0
+//                      = 2.0 - (1/x)*exp(-x*x-0.5625+R2/S2) if -6<x<0
+//                      = 2.0 - tiny            (if x <= -6)
+//              erf(x)  = sign(x)*(1.0 - erfc(x)) if x < 6, else
+//              erf(x)  = sign(x)*(1.0 - tiny)
+//         where
+//              R2(z) = degree 6 poly in z, (z=1/x**2)
+//              S2(z) = degree 7 poly in z
+//
+//      Note1:
+//         To compute exp(-x*x-0.5625+R/S), let s be a single
+//         precision number and s := x; then
+//              -x*x = -s*s + (s-x)*(s+x)
+//              exp(-x*x-0.5626+R/S) =
+//                      exp(-s*s-0.5625)*exp((s-x)*(s+x)+R/S);
+//      Note2:
+//         Here 4 and 5 make use of the asymptotic series
+//                        exp(-x*x)
+//              erfc(x) ~ ---------- * ( 1 + Poly(1/x**2) )
+//                        x*sqrt(pi)
+//         We use rational approximation to approximate
+//              g(s)=f(1/x**2) = log(erfc(x)*x) - x*x + 0.5625
+//         Here is the error bound for R1/S1 and R2/S2
+//              |R1/S1 - f(x)|  < 2**(-62.57)
+//              |R2/S2 - f(x)|  < 2**(-61.52)
+//
+//      5. For inf > x >= 28
+//              erf(x)  = sign(x) *(1 - tiny)  (raise inexact)
+//              erfc(x) = tiny*tiny (raise underflow) if x > 0
+//                      = 2 - tiny if x<0
+//
+//      7. Special case:
+//              erf(0)  = 0, erf(inf)  = 1, erf(-inf) = -1,
+//              erfc(0) = 1, erfc(inf) = 0, erfc(-inf) = 2,
+//              erfc/erf(NaN) is NaN
+
+const (
+	erx = 8.45062911510467529297e-01 // 0x3FEB0AC160000000
+	// Coefficients for approximation to  erf in [0, 0.84375]
+	efx  = 1.28379167095512586316e-01  // 0x3FC06EBA8214DB69
+	efx8 = 1.02703333676410069053e+00  // 0x3FF06EBA8214DB69
+	pp0  = 1.28379167095512558561e-01  // 0x3FC06EBA8214DB68
+	pp1  = -3.25042107247001499370e-01 // 0xBFD4CD7D691CB913
+	pp2  = -2.84817495755985104766e-02 // 0xBF9D2A51DBD7194F
+	pp3  = -5.77027029648944159157e-03 // 0xBF77A291236668E4
+	pp4  = -2.37630166566501626084e-05 // 0xBEF8EAD6120016AC
+	qq1  = 3.97917223959155352819e-01  // 0x3FD97779CDDADC09
+	qq2  = 6.50222499887672944485e-02  // 0x3FB0A54C5536CEBA
+	qq3  = 5.08130628187576562776e-03  // 0x3F74D022C4D36B0F
+	qq4  = 1.32494738004321644526e-04  // 0x3F215DC9221C1A10
+	qq5  = -3.96022827877536812320e-06 // 0xBED09C4342A26120
+	// Coefficients for approximation to  erf  in [0.84375, 1.25]
+	pa0 = -2.36211856075265944077e-03 // 0xBF6359B8BEF77538
+	pa1 = 4.14856118683748331666e-01  // 0x3FDA8D00AD92B34D
+	pa2 = -3.72207876035701323847e-01 // 0xBFD7D240FBB8C3F1
+	pa3 = 3.18346619901161753674e-01  // 0x3FD45FCA805120E4
+	pa4 = -1.10894694282396677476e-01 // 0xBFBC63983D3E28EC
+	pa5 = 3.54783043256182359371e-02  // 0x3FA22A36599795EB
+	pa6 = -2.16637559486879084300e-03 // 0xBF61BF380A96073F
+	qa1 = 1.06420880400844228286e-01  // 0x3FBB3E6618EEE323
+	qa2 = 5.40397917702171048937e-01  // 0x3FE14AF092EB6F33
+	qa3 = 7.18286544141962662868e-02  // 0x3FB2635CD99FE9A7
+	qa4 = 1.26171219808761642112e-01  // 0x3FC02660E763351F
+	qa5 = 1.36370839120290507362e-02  // 0x3F8BEDC26B51DD1C
+	qa6 = 1.19844998467991074170e-02  // 0x3F888B545735151D
+	// Coefficients for approximation to  erfc in [1.25, 1/0.35]
+	ra0 = -9.86494403484714822705e-03 // 0xBF843412600D6435
+	ra1 = -6.93858572707181764372e-01 // 0xBFE63416E4BA7360
+	ra2 = -1.05586262253232909814e+01 // 0xC0251E0441B0E726
+	ra3 = -6.23753324503260060396e+01 // 0xC04F300AE4CBA38D
+	ra4 = -1.62396669462573470355e+02 // 0xC0644CB184282266
+	ra5 = -1.84605092906711035994e+02 // 0xC067135CEBCCABB2
+	ra6 = -8.12874355063065934246e+01 // 0xC054526557E4D2F2
+	ra7 = -9.81432934416914548592e+00 // 0xC023A0EFC69AC25C
+	sa1 = 1.96512716674392571292e+01  // 0x4033A6B9BD707687
+	sa2 = 1.37657754143519042600e+02  // 0x4061350C526AE721
+	sa3 = 4.34565877475229228821e+02  // 0x407B290DD58A1A71
+	sa4 = 6.45387271733267880336e+02  // 0x40842B1921EC2868
+	sa5 = 4.29008140027567833386e+02  // 0x407AD02157700314
+	sa6 = 1.08635005541779435134e+02  // 0x405B28A3EE48AE2C
+	sa7 = 6.57024977031928170135e+00  // 0x401A47EF8E484A93
+	sa8 = -6.04244152148580987438e-02 // 0xBFAEEFF2EE749A62
+	// Coefficients for approximation to  erfc in [1/.35, 28]
+	rb0 = -9.86494292470009928597e-03 // 0xBF84341239E86F4A
+	rb1 = -7.99283237680523006574e-01 // 0xBFE993BA70C285DE
+	rb2 = -1.77579549177547519889e+01 // 0xC031C209555F995A
+	rb3 = -1.60636384855821916062e+02 // 0xC064145D43C5ED98
+	rb4 = -6.37566443368389627722e+02 // 0xC083EC881375F228
+	rb5 = -1.02509513161107724954e+03 // 0xC09004616A2E5992
+	rb6 = -4.83519191608651397019e+02 // 0xC07E384E9BDC383F
+	sb1 = 3.03380607434824582924e+01  // 0x403E568B261D5190
+	sb2 = 3.25792512996573918826e+02  // 0x40745CAE221B9F0A
+	sb3 = 1.53672958608443695994e+03  // 0x409802EB189D5118
+	sb4 = 3.19985821950859553908e+03  // 0x40A8FFB7688C246A
+	sb5 = 2.55305040643316442583e+03  // 0x40A3F219CEDF3BE6
+	sb6 = 4.74528541206955367215e+02  // 0x407DA874E79FE763
+	sb7 = -2.24409524465858183362e+01 // 0xC03670E242712D62
+)
+
+// Erf returns the error function of x.
+//
+// Special cases are:
+//	Erf(+Inf) = 1
+//	Erf(-Inf) = -1
+//	Erf(NaN) = NaN
+func Erf(x float64) float64 {
+	if haveArchErf {
+		return archErf(x)
+	}
+	return erf(x)
+}
+
+func erf(x float64) float64 {
+	const (
+		VeryTiny = 2.848094538889218e-306 // 0x0080000000000000
+		Small    = 1.0 / (1 << 28)        // 2**-28
+	)
+	// special cases
+	switch {
+	case IsNaN(x):
+		return NaN()
+	case IsInf(x, 1):
+		return 1
+	case IsInf(x, -1):
+		return -1
+	}
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+	if x < 0.84375 { // |x| < 0.84375
+		var temp float64
+		if x < Small { // |x| < 2**-28
+			if x < VeryTiny {
+				temp = 0.125 * (8.0*x + efx8*x) // avoid underflow
+			} else {
+				temp = x + efx*x
+			}
+		} else {
+			z := x * x
+			r := pp0 + z*(pp1+z*(pp2+z*(pp3+z*pp4)))
+			s := 1 + z*(qq1+z*(qq2+z*(qq3+z*(qq4+z*qq5))))
+			y := r / s
+			temp = x + x*y
+		}
+		if sign {
+			return -temp
+		}
+		return temp
+	}
+	if x < 1.25 { // 0.84375 <= |x| < 1.25
+		s := x - 1
+		P := pa0 + s*(pa1+s*(pa2+s*(pa3+s*(pa4+s*(pa5+s*pa6)))))
+		Q := 1 + s*(qa1+s*(qa2+s*(qa3+s*(qa4+s*(qa5+s*qa6)))))
+		if sign {
+			return -erx - P/Q
+		}
+		return erx + P/Q
+	}
+	if x >= 6 { // inf > |x| >= 6
+		if sign {
+			return -1
+		}
+		return 1
+	}
+	s := 1 / (x * x)
+	var R, S float64
+	if x < 1/0.35 { // |x| < 1 / 0.35  ~ 2.857143
+		R = ra0 + s*(ra1+s*(ra2+s*(ra3+s*(ra4+s*(ra5+s*(ra6+s*ra7))))))
+		S = 1 + s*(sa1+s*(sa2+s*(sa3+s*(sa4+s*(sa5+s*(sa6+s*(sa7+s*sa8)))))))
+	} else { // |x| >= 1 / 0.35  ~ 2.857143
+		R = rb0 + s*(rb1+s*(rb2+s*(rb3+s*(rb4+s*(rb5+s*rb6)))))
+		S = 1 + s*(sb1+s*(sb2+s*(sb3+s*(sb4+s*(sb5+s*(sb6+s*sb7))))))
+	}
+	z := Float64frombits(Float64bits(x) & 0xffffffff00000000) // pseudo-single (20-bit) precision x
+	r := Exp(-z*z-0.5625) * Exp((z-x)*(z+x)+R/S)
+	if sign {
+		return r/x - 1
+	}
+	return 1 - r/x
+}
+
+// Erfc returns the complementary error function of x.
+//
+// Special cases are:
+//	Erfc(+Inf) = 0
+//	Erfc(-Inf) = 2
+//	Erfc(NaN) = NaN
+func Erfc(x float64) float64 {
+	if haveArchErfc {
+		return archErfc(x)
+	}
+	return erfc(x)
+}
+
+func erfc(x float64) float64 {
+	const Tiny = 1.0 / (1 << 56) // 2**-56
+	// special cases
+	switch {
+	case IsNaN(x):
+		return NaN()
+	case IsInf(x, 1):
+		return 0
+	case IsInf(x, -1):
+		return 2
+	}
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+	if x < 0.84375 { // |x| < 0.84375
+		var temp float64
+		if x < Tiny { // |x| < 2**-56
+			temp = x
+		} else {
+			z := x * x
+			r := pp0 + z*(pp1+z*(pp2+z*(pp3+z*pp4)))
+			s := 1 + z*(qq1+z*(qq2+z*(qq3+z*(qq4+z*qq5))))
+			y := r / s
+			if x < 0.25 { // |x| < 1/4
+				temp = x + x*y
+			} else {
+				temp = 0.5 + (x*y + (x - 0.5))
+			}
+		}
+		if sign {
+			return 1 + temp
+		}
+		return 1 - temp
+	}
+	if x < 1.25 { // 0.84375 <= |x| < 1.25
+		s := x - 1
+		P := pa0 + s*(pa1+s*(pa2+s*(pa3+s*(pa4+s*(pa5+s*pa6)))))
+		Q := 1 + s*(qa1+s*(qa2+s*(qa3+s*(qa4+s*(qa5+s*qa6)))))
+		if sign {
+			return 1 + erx + P/Q
+		}
+		return 1 - erx - P/Q
+
+	}
+	if x < 28 { // |x| < 28
+		s := 1 / (x * x)
+		var R, S float64
+		if x < 1/0.35 { // |x| < 1 / 0.35 ~ 2.857143
+			R = ra0 + s*(ra1+s*(ra2+s*(ra3+s*(ra4+s*(ra5+s*(ra6+s*ra7))))))
+			S = 1 + s*(sa1+s*(sa2+s*(sa3+s*(sa4+s*(sa5+s*(sa6+s*(sa7+s*sa8)))))))
+		} else { // |x| >= 1 / 0.35 ~ 2.857143
+			if sign && x > 6 {
+				return 2 // x < -6
+			}
+			R = rb0 + s*(rb1+s*(rb2+s*(rb3+s*(rb4+s*(rb5+s*rb6)))))
+			S = 1 + s*(sb1+s*(sb2+s*(sb3+s*(sb4+s*(sb5+s*(sb6+s*sb7))))))
+		}
+		z := Float64frombits(Float64bits(x) & 0xffffffff00000000) // pseudo-single (20-bit) precision x
+		r := Exp(-z*z-0.5625) * Exp((z-x)*(z+x)+R/S)
+		if sign {
+			return 2 - r/x
+		}
+		return r / x
+	}
+	if sign {
+		return 2
+	}
+	return 0
+}
diff --git a/contrib/go/_std_1.18/src/math/erfinv.go b/contrib/go/_std_1.18/src/math/erfinv.go
new file mode 100644
index 0000000000..ee423d33e4
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/erfinv.go
@@ -0,0 +1,127 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Inverse of the floating-point error function.
+*/
+
+// This implementation is based on the rational approximation
+// of percentage points of normal distribution available from
+// https://www.jstor.org/stable/2347330.
+
+const (
+	// Coefficients for approximation to erf in |x| <= 0.85
+	a0 = 1.1975323115670912564578e0
+	a1 = 4.7072688112383978012285e1
+	a2 = 6.9706266534389598238465e2
+	a3 = 4.8548868893843886794648e3
+	a4 = 1.6235862515167575384252e4
+	a5 = 2.3782041382114385731252e4
+	a6 = 1.1819493347062294404278e4
+	a7 = 8.8709406962545514830200e2
+	b0 = 1.0000000000000000000e0
+	b1 = 4.2313330701600911252e1
+	b2 = 6.8718700749205790830e2
+	b3 = 5.3941960214247511077e3
+	b4 = 2.1213794301586595867e4
+	b5 = 3.9307895800092710610e4
+	b6 = 2.8729085735721942674e4
+	b7 = 5.2264952788528545610e3
+	// Coefficients for approximation to erf in 0.85 < |x| <= 1-2*exp(-25)
+	c0 = 1.42343711074968357734e0
+	c1 = 4.63033784615654529590e0
+	c2 = 5.76949722146069140550e0
+	c3 = 3.64784832476320460504e0
+	c4 = 1.27045825245236838258e0
+	c5 = 2.41780725177450611770e-1
+	c6 = 2.27238449892691845833e-2
+	c7 = 7.74545014278341407640e-4
+	d0 = 1.4142135623730950488016887e0
+	d1 = 2.9036514445419946173133295e0
+	d2 = 2.3707661626024532365971225e0
+	d3 = 9.7547832001787427186894837e-1
+	d4 = 2.0945065210512749128288442e-1
+	d5 = 2.1494160384252876777097297e-2
+	d6 = 7.7441459065157709165577218e-4
+	d7 = 1.4859850019840355905497876e-9
+	// Coefficients for approximation to erf in 1-2*exp(-25) < |x| < 1
+	e0 = 6.65790464350110377720e0
+	e1 = 5.46378491116411436990e0
+	e2 = 1.78482653991729133580e0
+	e3 = 2.96560571828504891230e-1
+	e4 = 2.65321895265761230930e-2
+	e5 = 1.24266094738807843860e-3
+	e6 = 2.71155556874348757815e-5
+	e7 = 2.01033439929228813265e-7
+	f0 = 1.414213562373095048801689e0
+	f1 = 8.482908416595164588112026e-1
+	f2 = 1.936480946950659106176712e-1
+	f3 = 2.103693768272068968719679e-2
+	f4 = 1.112800997078859844711555e-3
+	f5 = 2.611088405080593625138020e-5
+	f6 = 2.010321207683943062279931e-7
+	f7 = 2.891024605872965461538222e-15
+)
+
+// Erfinv returns the inverse error function of x.
+//
+// Special cases are:
+//	Erfinv(1) = +Inf
+//	Erfinv(-1) = -Inf
+//	Erfinv(x) = NaN if x < -1 or x > 1
+//	Erfinv(NaN) = NaN
+func Erfinv(x float64) float64 {
+	// special cases
+	if IsNaN(x) || x <= -1 || x >= 1 {
+		if x == -1 || x == 1 {
+			return Inf(int(x))
+		}
+		return NaN()
+	}
+
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+
+	var ans float64
+	if x <= 0.85 { // |x| <= 0.85
+		r := 0.180625 - 0.25*x*x
+		z1 := ((((((a7*r+a6)*r+a5)*r+a4)*r+a3)*r+a2)*r+a1)*r + a0
+		z2 := ((((((b7*r+b6)*r+b5)*r+b4)*r+b3)*r+b2)*r+b1)*r + b0
+		ans = (x * z1) / z2
+	} else {
+		var z1, z2 float64
+		r := Sqrt(Ln2 - Log(1.0-x))
+		if r <= 5.0 {
+			r -= 1.6
+			z1 = ((((((c7*r+c6)*r+c5)*r+c4)*r+c3)*r+c2)*r+c1)*r + c0
+			z2 = ((((((d7*r+d6)*r+d5)*r+d4)*r+d3)*r+d2)*r+d1)*r + d0
+		} else {
+			r -= 5.0
+			z1 = ((((((e7*r+e6)*r+e5)*r+e4)*r+e3)*r+e2)*r+e1)*r + e0
+			z2 = ((((((f7*r+f6)*r+f5)*r+f4)*r+f3)*r+f2)*r+f1)*r + f0
+		}
+		ans = z1 / z2
+	}
+
+	if sign {
+		return -ans
+	}
+	return ans
+}
+
+// Erfcinv returns the inverse of Erfc(x).
+//
+// Special cases are:
+//	Erfcinv(0) = +Inf
+//	Erfcinv(2) = -Inf
+//	Erfcinv(x) = NaN if x < 0 or x > 2
+//	Erfcinv(NaN) = NaN
+func Erfcinv(x float64) float64 {
+	return Erfinv(1 - x)
+}
diff --git a/contrib/go/_std_1.18/src/math/exp.go b/contrib/go/_std_1.18/src/math/exp.go
new file mode 100644
index 0000000000..d05eb91fb0
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/exp.go
@@ -0,0 +1,201 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Exp returns e**x, the base-e exponential of x.
+//
+// Special cases are:
+//	Exp(+Inf) = +Inf
+//	Exp(NaN) = NaN
+// Very large values overflow to 0 or +Inf.
+// Very small values underflow to 1.
+func Exp(x float64) float64 {
+	if haveArchExp {
+		return archExp(x)
+	}
+	return exp(x)
+}
+
+// The original C code, the long comment, and the constants
+// below are from FreeBSD's /usr/src/lib/msun/src/e_exp.c
+// and came with this notice. The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 2004 by Sun Microsystems, Inc. All rights reserved.
+//
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+//
+// exp(x)
+// Returns the exponential of x.
+//
+// Method
+//   1. Argument reduction:
+//      Reduce x to an r so that |r| <= 0.5*ln2 ~ 0.34658.
+//      Given x, find r and integer k such that
+//
+//               x = k*ln2 + r,  |r| <= 0.5*ln2.
+//
+//      Here r will be represented as r = hi-lo for better
+//      accuracy.
+//
+//   2. Approximation of exp(r) by a special rational function on
+//      the interval [0,0.34658]:
+//      Write
+//          R(r**2) = r*(exp(r)+1)/(exp(r)-1) = 2 + r*r/6 - r**4/360 + ...
+//      We use a special Remez algorithm on [0,0.34658] to generate
+//      a polynomial of degree 5 to approximate R. The maximum error
+//      of this polynomial approximation is bounded by 2**-59. In
+//      other words,
+//          R(z) ~ 2.0 + P1*z + P2*z**2 + P3*z**3 + P4*z**4 + P5*z**5
+//      (where z=r*r, and the values of P1 to P5 are listed below)
+//      and
+//          |                  5          |     -59
+//          | 2.0+P1*z+...+P5*z   -  R(z) | <= 2
+//          |                             |
+//      The computation of exp(r) thus becomes
+//                             2*r
+//              exp(r) = 1 + -------
+//                            R - r
+//                                 r*R1(r)
+//                     = 1 + r + ----------- (for better accuracy)
+//                                2 - R1(r)
+//      where
+//                               2       4             10
+//              R1(r) = r - (P1*r  + P2*r  + ... + P5*r   ).
+//
+//   3. Scale back to obtain exp(x):
+//      From step 1, we have
+//         exp(x) = 2**k * exp(r)
+//
+// Special cases:
+//      exp(INF) is INF, exp(NaN) is NaN;
+//      exp(-INF) is 0, and
+//      for finite argument, only exp(0)=1 is exact.
+//
+// Accuracy:
+//      according to an error analysis, the error is always less than
+//      1 ulp (unit in the last place).
+//
+// Misc. info.
+//      For IEEE double
+//          if x >  7.09782712893383973096e+02 then exp(x) overflow
+//          if x < -7.45133219101941108420e+02 then exp(x) underflow
+//
+// Constants:
+// The hexadecimal values are the intended ones for the following
+// constants. The decimal values may be used, provided that the
+// compiler will convert from decimal to binary accurately enough
+// to produce the hexadecimal values shown.
+
+func exp(x float64) float64 {
+	const (
+		Ln2Hi = 6.93147180369123816490e-01
+		Ln2Lo = 1.90821492927058770002e-10
+		Log2e = 1.44269504088896338700e+00
+
+		Overflow  = 7.09782712893383973096e+02
+		Underflow = -7.45133219101941108420e+02
+		NearZero  = 1.0 / (1 << 28) // 2**-28
+	)
+
+	// special cases
+	switch {
+	case IsNaN(x) || IsInf(x, 1):
+		return x
+	case IsInf(x, -1):
+		return 0
+	case x > Overflow:
+		return Inf(1)
+	case x < Underflow:
+		return 0
+	case -NearZero < x && x < NearZero:
+		return 1 + x
+	}
+
+	// reduce; computed as r = hi - lo for extra precision.
+	var k int
+	switch {
+	case x < 0:
+		k = int(Log2e*x - 0.5)
+	case x > 0:
+		k = int(Log2e*x + 0.5)
+	}
+	hi := x - float64(k)*Ln2Hi
+	lo := float64(k) * Ln2Lo
+
+	// compute
+	return expmulti(hi, lo, k)
+}
+
+// Exp2 returns 2**x, the base-2 exponential of x.
+//
+// Special cases are the same as Exp.
+func Exp2(x float64) float64 {
+	if haveArchExp2 {
+		return archExp2(x)
+	}
+	return exp2(x)
+}
+
+func exp2(x float64) float64 {
+	const (
+		Ln2Hi = 6.93147180369123816490e-01
+		Ln2Lo = 1.90821492927058770002e-10
+
+		Overflow  = 1.0239999999999999e+03
+		Underflow = -1.0740e+03
+	)
+
+	// special cases
+	switch {
+	case IsNaN(x) || IsInf(x, 1):
+		return x
+	case IsInf(x, -1):
+		return 0
+	case x > Overflow:
+		return Inf(1)
+	case x < Underflow:
+		return 0
+	}
+
+	// argument reduction; x = r×lg(e) + k with |r| ≤ ln(2)/2.
+	// computed as r = hi - lo for extra precision.
+	var k int
+	switch {
+	case x > 0:
+		k = int(x + 0.5)
+	case x < 0:
+		k = int(x - 0.5)
+	}
+	t := x - float64(k)
+	hi := t * Ln2Hi
+	lo := -t * Ln2Lo
+
+	// compute
+	return expmulti(hi, lo, k)
+}
+
+// exp1 returns e**r × 2**k where r = hi - lo and |r| ≤ ln(2)/2.
+func expmulti(hi, lo float64, k int) float64 {
+	const (
+		P1 = 1.66666666666666657415e-01  /* 0x3FC55555; 0x55555555 */
+		P2 = -2.77777777770155933842e-03 /* 0xBF66C16C; 0x16BEBD93 */
+		P3 = 6.61375632143793436117e-05  /* 0x3F11566A; 0xAF25DE2C */
+		P4 = -1.65339022054652515390e-06 /* 0xBEBBBD41; 0xC5D26BF1 */
+		P5 = 4.13813679705723846039e-08  /* 0x3E663769; 0x72BEA4D0 */
+	)
+
+	r := hi - lo
+	t := r * r
+	c := r - t*(P1+t*(P2+t*(P3+t*(P4+t*P5))))
+	y := 1 - ((lo - (r*c)/(2-c)) - hi)
+	// TODO(rsc): make sure Ldexp can handle boundary k
+	return Ldexp(y, k)
+}
diff --git a/contrib/go/_std_1.18/src/math/exp2_noasm.go b/contrib/go/_std_1.18/src/math/exp2_noasm.go
new file mode 100644
index 0000000000..c2b409329f
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/exp2_noasm.go
@@ -0,0 +1,13 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !arm64
+
+package math
+
+const haveArchExp2 = false
+
+func archExp2(x float64) float64 {
+	panic("not implemented")
+}
diff --git a/contrib/go/_std_1.18/src/math/exp_amd64.go b/contrib/go/_std_1.18/src/math/exp_amd64.go
new file mode 100644
index 0000000000..0f701b1d6d
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/exp_amd64.go
@@ -0,0 +1,11 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build amd64
+
+package math
+
+import "internal/cpu"
+
+var useFMA = cpu.X86.HasAVX && cpu.X86.HasFMA
diff --git a/contrib/go/_std_1.18/src/math/exp_amd64.s b/contrib/go/_std_1.18/src/math/exp_amd64.s
new file mode 100644
index 0000000000..02b71c81eb
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/exp_amd64.s
@@ -0,0 +1,159 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "textflag.h"
+
+// The method is based on a paper by Naoki Shibata: "Efficient evaluation
+// methods of elementary functions suitable for SIMD computation", Proc.
+// of International Supercomputing Conference 2010 (ISC'10), pp. 25 -- 32
+// (May 2010). The paper is available at
+// https://link.springer.com/article/10.1007/s00450-010-0108-2
+//
+// The original code and the constants below are from the author's
+// implementation available at http://freshmeat.net/projects/sleef.
+// The README file says, "The software is in public domain.
+// You can use the software without any obligation."
+//
+// This code is a simplified version of the original.
+
+#define LN2 0.6931471805599453094172321214581766 // log_e(2)
+#define LOG2E 1.4426950408889634073599246810018920 // 1/LN2
+#define LN2U 0.69314718055966295651160180568695068359375 // upper half LN2
+#define LN2L 0.28235290563031577122588448175013436025525412068e-12 // lower half LN2
+#define PosInf 0x7FF0000000000000
+#define NegInf 0xFFF0000000000000
+#define Overflow 7.09782712893384e+02
+
+DATA exprodata<>+0(SB)/8, $0.5
+DATA exprodata<>+8(SB)/8, $1.0
+DATA exprodata<>+16(SB)/8, $2.0
+DATA exprodata<>+24(SB)/8, $1.6666666666666666667e-1
+DATA exprodata<>+32(SB)/8, $4.1666666666666666667e-2
+DATA exprodata<>+40(SB)/8, $8.3333333333333333333e-3
+DATA exprodata<>+48(SB)/8, $1.3888888888888888889e-3
+DATA exprodata<>+56(SB)/8, $1.9841269841269841270e-4
+DATA exprodata<>+64(SB)/8, $2.4801587301587301587e-5
+GLOBL exprodata<>+0(SB), RODATA, $72
+
+// func Exp(x float64) float64
+TEXT ·archExp(SB),NOSPLIT,$0
+	// test bits for not-finite
+	MOVQ    x+0(FP), BX
+	MOVQ    $~(1<<63), AX // sign bit mask
+	MOVQ    BX, DX
+	ANDQ    AX, DX
+	MOVQ    $PosInf, AX
+	CMPQ    AX, DX
+	JLE     notFinite
+	// check if argument will overflow
+	MOVQ    BX, X0
+	MOVSD   $Overflow, X1
+	COMISD  X1, X0
+	JA      overflow
+	MOVSD   $LOG2E, X1
+	MULSD   X0, X1
+	CVTSD2SL X1, BX // BX = exponent
+	CVTSL2SD BX, X1
+	CMPB ·useFMA(SB), $1
+	JE   avxfma
+	MOVSD   $LN2U, X2
+	MULSD   X1, X2
+	SUBSD   X2, X0
+	MOVSD   $LN2L, X2
+	MULSD   X1, X2
+	SUBSD   X2, X0
+	// reduce argument
+	MULSD   $0.0625, X0
+	// Taylor series evaluation
+	MOVSD   exprodata<>+64(SB), X1
+	MULSD   X0, X1
+	ADDSD   exprodata<>+56(SB), X1
+	MULSD   X0, X1
+	ADDSD   exprodata<>+48(SB), X1
+	MULSD   X0, X1
+	ADDSD   exprodata<>+40(SB), X1
+	MULSD   X0, X1
+	ADDSD   exprodata<>+32(SB), X1
+	MULSD   X0, X1
+	ADDSD   exprodata<>+24(SB), X1
+	MULSD   X0, X1
+	ADDSD   exprodata<>+0(SB), X1
+	MULSD   X0, X1
+	ADDSD   exprodata<>+8(SB), X1
+	MULSD   X1, X0
+	MOVSD   exprodata<>+16(SB), X1
+	ADDSD   X0, X1
+	MULSD   X1, X0
+	MOVSD   exprodata<>+16(SB), X1
+	ADDSD   X0, X1
+	MULSD   X1, X0
+	MOVSD   exprodata<>+16(SB), X1
+	ADDSD   X0, X1
+	MULSD   X1, X0
+	MOVSD   exprodata<>+16(SB), X1
+	ADDSD   X0, X1
+	MULSD   X1, X0
+	ADDSD exprodata<>+8(SB), X0
+	// return fr * 2**exponent
+ldexp:
+	ADDL    $0x3FF, BX // add bias
+	JLE     denormal
+	CMPL    BX, $0x7FF
+	JGE     overflow
+lastStep:
+	SHLQ    $52, BX
+	MOVQ    BX, X1
+	MULSD   X1, X0
+	MOVSD   X0, ret+8(FP)
+	RET
+notFinite:
+	// test bits for -Inf
+	MOVQ    $NegInf, AX
+	CMPQ    AX, BX
+	JNE     notNegInf
+	// -Inf, return 0
+underflow: // return 0
+	MOVQ    $0, ret+8(FP)
+	RET
+overflow: // return +Inf
+	MOVQ    $PosInf, BX
+notNegInf: // NaN or +Inf, return x
+	MOVQ    BX, ret+8(FP)
+	RET
+denormal:
+	CMPL    BX, $-52
+	JL      underflow
+	ADDL    $0x3FE, BX // add bias - 1
+	SHLQ    $52, BX
+	MOVQ    BX, X1
+	MULSD   X1, X0
+	MOVQ    $1, BX
+	JMP     lastStep
+
+avxfma:
+	MOVSD   $LN2U, X2
+	VFNMADD231SD X2, X1, X0
+	MOVSD   $LN2L, X2
+	VFNMADD231SD X2, X1, X0
+	// reduce argument
+	MULSD   $0.0625, X0
+	// Taylor series evaluation
+	MOVSD   exprodata<>+64(SB), X1
+	VFMADD213SD exprodata<>+56(SB), X0, X1
+	VFMADD213SD exprodata<>+48(SB), X0, X1
+	VFMADD213SD exprodata<>+40(SB), X0, X1
+	VFMADD213SD exprodata<>+32(SB), X0, X1
+	VFMADD213SD exprodata<>+24(SB), X0, X1
+	VFMADD213SD exprodata<>+0(SB), X0, X1
+	VFMADD213SD exprodata<>+8(SB), X0, X1
+	MULSD   X1, X0
+	VADDSD exprodata<>+16(SB), X0, X1
+	MULSD   X1, X0
+	VADDSD exprodata<>+16(SB), X0, X1
+	MULSD   X1, X0
+	VADDSD exprodata<>+16(SB), X0, X1
+	MULSD   X1, X0
+	VADDSD exprodata<>+16(SB), X0, X1
+	VFMADD213SD   exprodata<>+8(SB), X1, X0
+	JMP ldexp
diff --git a/contrib/go/_std_1.18/src/math/exp_asm.go b/contrib/go/_std_1.18/src/math/exp_asm.go
new file mode 100644
index 0000000000..424442845b
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/exp_asm.go
@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build amd64 || arm64 || s390x
+
+package math
+
+const haveArchExp = true
+
+func archExp(x float64) float64
diff --git a/contrib/go/_std_1.18/src/math/expm1.go b/contrib/go/_std_1.18/src/math/expm1.go
new file mode 100644
index 0000000000..66d3421661
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/expm1.go
@@ -0,0 +1,242 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// The original C code, the long comment, and the constants
+// below are from FreeBSD's /usr/src/lib/msun/src/s_expm1.c
+// and came with this notice. The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+// expm1(x)
+// Returns exp(x)-1, the exponential of x minus 1.
+//
+// Method
+//   1. Argument reduction:
+//      Given x, find r and integer k such that
+//
+//               x = k*ln2 + r,  |r| <= 0.5*ln2 ~ 0.34658
+//
+//      Here a correction term c will be computed to compensate
+//      the error in r when rounded to a floating-point number.
+//
+//   2. Approximating expm1(r) by a special rational function on
+//      the interval [0,0.34658]:
+//      Since
+//          r*(exp(r)+1)/(exp(r)-1) = 2+ r**2/6 - r**4/360 + ...
+//      we define R1(r*r) by
+//          r*(exp(r)+1)/(exp(r)-1) = 2+ r**2/6 * R1(r*r)
+//      That is,
+//          R1(r**2) = 6/r *((exp(r)+1)/(exp(r)-1) - 2/r)
+//                   = 6/r * ( 1 + 2.0*(1/(exp(r)-1) - 1/r))
+//                   = 1 - r**2/60 + r**4/2520 - r**6/100800 + ...
+//      We use a special Reme algorithm on [0,0.347] to generate
+//      a polynomial of degree 5 in r*r to approximate R1. The
+//      maximum error of this polynomial approximation is bounded
+//      by 2**-61. In other words,
+//          R1(z) ~ 1.0 + Q1*z + Q2*z**2 + Q3*z**3 + Q4*z**4 + Q5*z**5
+//      where   Q1  =  -1.6666666666666567384E-2,
+//              Q2  =   3.9682539681370365873E-4,
+//              Q3  =  -9.9206344733435987357E-6,
+//              Q4  =   2.5051361420808517002E-7,
+//              Q5  =  -6.2843505682382617102E-9;
+//      (where z=r*r, and the values of Q1 to Q5 are listed below)
+//      with error bounded by
+//          |                  5           |     -61
+//          | 1.0+Q1*z+...+Q5*z   -  R1(z) | <= 2
+//          |                              |
+//
+//      expm1(r) = exp(r)-1 is then computed by the following
+//      specific way which minimize the accumulation rounding error:
+//                             2     3
+//                            r     r    [ 3 - (R1 + R1*r/2)  ]
+//            expm1(r) = r + --- + --- * [--------------------]
+//                            2     2    [ 6 - r*(3 - R1*r/2) ]
+//
+//      To compensate the error in the argument reduction, we use
+//              expm1(r+c) = expm1(r) + c + expm1(r)*c
+//                         ~ expm1(r) + c + r*c
+//      Thus c+r*c will be added in as the correction terms for
+//      expm1(r+c). Now rearrange the term to avoid optimization
+//      screw up:
+//                      (      2                                    2 )
+//                      ({  ( r    [ R1 -  (3 - R1*r/2) ]  )  }    r  )
+//       expm1(r+c)~r - ({r*(--- * [--------------------]-c)-c} - --- )
+//                      ({  ( 2    [ 6 - r*(3 - R1*r/2) ]  )  }    2  )
+//                      (                                             )
+//
+//                 = r - E
+//   3. Scale back to obtain expm1(x):
+//      From step 1, we have
+//         expm1(x) = either 2**k*[expm1(r)+1] - 1
+//                  = or     2**k*[expm1(r) + (1-2**-k)]
+//   4. Implementation notes:
+//      (A). To save one multiplication, we scale the coefficient Qi
+//           to Qi*2**i, and replace z by (x**2)/2.
+//      (B). To achieve maximum accuracy, we compute expm1(x) by
+//        (i)   if x < -56*ln2, return -1.0, (raise inexact if x!=inf)
+//        (ii)  if k=0, return r-E
+//        (iii) if k=-1, return 0.5*(r-E)-0.5
+//        (iv)  if k=1 if r < -0.25, return 2*((r+0.5)- E)
+//                     else          return  1.0+2.0*(r-E);
+//        (v)   if (k<-2||k>56) return 2**k(1-(E-r)) - 1 (or exp(x)-1)
+//        (vi)  if k <= 20, return 2**k((1-2**-k)-(E-r)), else
+//        (vii) return 2**k(1-((E+2**-k)-r))
+//
+// Special cases:
+//      expm1(INF) is INF, expm1(NaN) is NaN;
+//      expm1(-INF) is -1, and
+//      for finite argument, only expm1(0)=0 is exact.
+//
+// Accuracy:
+//      according to an error analysis, the error is always less than
+//      1 ulp (unit in the last place).
+//
+// Misc. info.
+//      For IEEE double
+//          if x >  7.09782712893383973096e+02 then expm1(x) overflow
+//
+// Constants:
+// The hexadecimal values are the intended ones for the following
+// constants. The decimal values may be used, provided that the
+// compiler will convert from decimal to binary accurately enough
+// to produce the hexadecimal values shown.
+//
+
+// Expm1 returns e**x - 1, the base-e exponential of x minus 1.
+// It is more accurate than Exp(x) - 1 when x is near zero.
+//
+// Special cases are:
+//	Expm1(+Inf) = +Inf
+//	Expm1(-Inf) = -1
+//	Expm1(NaN) = NaN
+// Very large values overflow to -1 or +Inf.
+func Expm1(x float64) float64 {
+	if haveArchExpm1 {
+		return archExpm1(x)
+	}
+	return expm1(x)
+}
+
+func expm1(x float64) float64 {
+	const (
+		Othreshold = 7.09782712893383973096e+02 // 0x40862E42FEFA39EF
+		Ln2X56     = 3.88162421113569373274e+01 // 0x4043687a9f1af2b1
+		Ln2HalfX3  = 1.03972077083991796413e+00 // 0x3ff0a2b23f3bab73
+		Ln2Half    = 3.46573590279972654709e-01 // 0x3fd62e42fefa39ef
+		Ln2Hi      = 6.93147180369123816490e-01 // 0x3fe62e42fee00000
+		Ln2Lo      = 1.90821492927058770002e-10 // 0x3dea39ef35793c76
+		InvLn2     = 1.44269504088896338700e+00 // 0x3ff71547652b82fe
+		Tiny       = 1.0 / (1 << 54)            // 2**-54 = 0x3c90000000000000
+		// scaled coefficients related to expm1
+		Q1 = -3.33333333333331316428e-02 // 0xBFA11111111110F4
+		Q2 = 1.58730158725481460165e-03  // 0x3F5A01A019FE5585
+		Q3 = -7.93650757867487942473e-05 // 0xBF14CE199EAADBB7
+		Q4 = 4.00821782732936239552e-06  // 0x3ED0CFCA86E65239
+		Q5 = -2.01099218183624371326e-07 // 0xBE8AFDB76E09C32D
+	)
+
+	// special cases
+	switch {
+	case IsInf(x, 1) || IsNaN(x):
+		return x
+	case IsInf(x, -1):
+		return -1
+	}
+
+	absx := x
+	sign := false
+	if x < 0 {
+		absx = -absx
+		sign = true
+	}
+
+	// filter out huge argument
+	if absx >= Ln2X56 { // if |x| >= 56 * ln2
+		if sign {
+			return -1 // x < -56*ln2, return -1
+		}
+		if absx >= Othreshold { // if |x| >= 709.78...
+			return Inf(1)
+		}
+	}
+
+	// argument reduction
+	var c float64
+	var k int
+	if absx > Ln2Half { // if  |x| > 0.5 * ln2
+		var hi, lo float64
+		if absx < Ln2HalfX3 { // and |x| < 1.5 * ln2
+			if !sign {
+				hi = x - Ln2Hi
+				lo = Ln2Lo
+				k = 1
+			} else {
+				hi = x + Ln2Hi
+				lo = -Ln2Lo
+				k = -1
+			}
+		} else {
+			if !sign {
+				k = int(InvLn2*x + 0.5)
+			} else {
+				k = int(InvLn2*x - 0.5)
+			}
+			t := float64(k)
+			hi = x - t*Ln2Hi // t * Ln2Hi is exact here
+			lo = t * Ln2Lo
+		}
+		x = hi - lo
+		c = (hi - x) - lo
+	} else if absx < Tiny { // when |x| < 2**-54, return x
+		return x
+	} else {
+		k = 0
+	}
+
+	// x is now in primary range
+	hfx := 0.5 * x
+	hxs := x * hfx
+	r1 := 1 + hxs*(Q1+hxs*(Q2+hxs*(Q3+hxs*(Q4+hxs*Q5))))
+	t := 3 - r1*hfx
+	e := hxs * ((r1 - t) / (6.0 - x*t))
+	if k == 0 {
+		return x - (x*e - hxs) // c is 0
+	}
+	e = (x*(e-c) - c)
+	e -= hxs
+	switch {
+	case k == -1:
+		return 0.5*(x-e) - 0.5
+	case k == 1:
+		if x < -0.25 {
+			return -2 * (e - (x + 0.5))
+		}
+		return 1 + 2*(x-e)
+	case k <= -2 || k > 56: // suffice to return exp(x)-1
+		y := 1 - (e - x)
+		y = Float64frombits(Float64bits(y) + uint64(k)<<52) // add k to y's exponent
+		return y - 1
+	}
+	if k < 20 {
+		t := Float64frombits(0x3ff0000000000000 - (0x20000000000000 >> uint(k))) // t=1-2**-k
+		y := t - (e - x)
+		y = Float64frombits(Float64bits(y) + uint64(k)<<52) // add k to y's exponent
+		return y
+	}
+	t = Float64frombits(uint64(0x3ff-k) << 52) // 2**-k
+	y := x - (e + t)
+	y++
+	y = Float64frombits(Float64bits(y) + uint64(k)<<52) // add k to y's exponent
+	return y
+}
diff --git a/contrib/go/_std_1.18/src/math/floor.go b/contrib/go/_std_1.18/src/math/floor.go
new file mode 100644
index 0000000000..7913a900e3
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/floor.go
@@ -0,0 +1,146 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Floor returns the greatest integer value less than or equal to x.
+//
+// Special cases are:
+//	Floor(±0) = ±0
+//	Floor(±Inf) = ±Inf
+//	Floor(NaN) = NaN
+func Floor(x float64) float64 {
+	if haveArchFloor {
+		return archFloor(x)
+	}
+	return floor(x)
+}
+
+func floor(x float64) float64 {
+	if x == 0 || IsNaN(x) || IsInf(x, 0) {
+		return x
+	}
+	if x < 0 {
+		d, fract := Modf(-x)
+		if fract != 0.0 {
+			d = d + 1
+		}
+		return -d
+	}
+	d, _ := Modf(x)
+	return d
+}
+
+// Ceil returns the least integer value greater than or equal to x.
+//
+// Special cases are:
+//	Ceil(±0) = ±0
+//	Ceil(±Inf) = ±Inf
+//	Ceil(NaN) = NaN
+func Ceil(x float64) float64 {
+	if haveArchCeil {
+		return archCeil(x)
+	}
+	return ceil(x)
+}
+
+func ceil(x float64) float64 {
+	return -Floor(-x)
+}
+
+// Trunc returns the integer value of x.
+//
+// Special cases are:
+//	Trunc(±0) = ±0
+//	Trunc(±Inf) = ±Inf
+//	Trunc(NaN) = NaN
+func Trunc(x float64) float64 {
+	if haveArchTrunc {
+		return archTrunc(x)
+	}
+	return trunc(x)
+}
+
+func trunc(x float64) float64 {
+	if x == 0 || IsNaN(x) || IsInf(x, 0) {
+		return x
+	}
+	d, _ := Modf(x)
+	return d
+}
+
+// Round returns the nearest integer, rounding half away from zero.
+//
+// Special cases are:
+//	Round(±0) = ±0
+//	Round(±Inf) = ±Inf
+//	Round(NaN) = NaN
+func Round(x float64) float64 {
+	// Round is a faster implementation of:
+	//
+	// func Round(x float64) float64 {
+	//   t := Trunc(x)
+	//   if Abs(x-t) >= 0.5 {
+	//     return t + Copysign(1, x)
+	//   }
+	//   return t
+	// }
+	bits := Float64bits(x)
+	e := uint(bits>>shift) & mask
+	if e < bias {
+		// Round abs(x) < 1 including denormals.
+		bits &= signMask // +-0
+		if e == bias-1 {
+			bits |= uvone // +-1
+		}
+	} else if e < bias+shift {
+		// Round any abs(x) >= 1 containing a fractional component [0,1).
+		//
+		// Numbers with larger exponents are returned unchanged since they
+		// must be either an integer, infinity, or NaN.
+		const half = 1 << (shift - 1)
+		e -= bias
+		bits += half >> e
+		bits &^= fracMask >> e
+	}
+	return Float64frombits(bits)
+}
+
+// RoundToEven returns the nearest integer, rounding ties to even.
+//
+// Special cases are:
+//	RoundToEven(±0) = ±0
+//	RoundToEven(±Inf) = ±Inf
+//	RoundToEven(NaN) = NaN
+func RoundToEven(x float64) float64 {
+	// RoundToEven is a faster implementation of:
+	//
+	// func RoundToEven(x float64) float64 {
+	//   t := math.Trunc(x)
+	//   odd := math.Remainder(t, 2) != 0
+	//   if d := math.Abs(x - t); d > 0.5 || (d == 0.5 && odd) {
+	//     return t + math.Copysign(1, x)
+	//   }
+	//   return t
+	// }
+	bits := Float64bits(x)
+	e := uint(bits>>shift) & mask
+	if e >= bias {
+		// Round abs(x) >= 1.
+		// - Large numbers without fractional components, infinity, and NaN are unchanged.
+		// - Add 0.499.. or 0.5 before truncating depending on whether the truncated
+		//   number is even or odd (respectively).
+		const halfMinusULP = (1 << (shift - 1)) - 1
+		e -= bias
+		bits += (halfMinusULP + (bits>>(shift-e))&1) >> e
+		bits &^= fracMask >> e
+	} else if e == bias-1 && bits&fracMask != 0 {
+		// Round 0.5 < abs(x) < 1.
+		bits = bits&signMask | uvone // +-1
+	} else {
+		// Round abs(x) <= 0.5 including denormals.
+		bits &= signMask // +-0
+	}
+	return Float64frombits(bits)
+}
diff --git a/contrib/go/_std_1.18/src/math/floor_amd64.s b/contrib/go/_std_1.18/src/math/floor_amd64.s
new file mode 100644
index 0000000000..088049958a
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/floor_amd64.s
@@ -0,0 +1,76 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "textflag.h"
+
+#define Big		0x4330000000000000 // 2**52
+
+// func archFloor(x float64) float64
+TEXT ·archFloor(SB),NOSPLIT,$0
+	MOVQ	x+0(FP), AX
+	MOVQ	$~(1<<63), DX // sign bit mask
+	ANDQ	AX,DX // DX = |x|
+	SUBQ	$1,DX
+	MOVQ    $(Big - 1), CX // if |x| >= 2**52-1 or IsNaN(x) or |x| == 0, return x
+	CMPQ	DX,CX
+	JAE     isBig_floor
+	MOVQ	AX, X0 // X0 = x
+	CVTTSD2SQ	X0, AX
+	CVTSQ2SD	AX, X1 // X1 = float(int(x))
+	CMPSD	X1, X0, 1 // compare LT; X0 = 0xffffffffffffffff or 0
+	MOVSD	$(-1.0), X2
+	ANDPD	X2, X0 // if x < float(int(x)) {X0 = -1} else {X0 = 0}
+	ADDSD	X1, X0
+	MOVSD	X0, ret+8(FP)
+	RET
+isBig_floor:
+	MOVQ    AX, ret+8(FP) // return x
+	RET
+
+// func archCeil(x float64) float64
+TEXT ·archCeil(SB),NOSPLIT,$0
+	MOVQ	x+0(FP), AX
+	MOVQ	$~(1<<63), DX // sign bit mask
+	MOVQ	AX, BX // BX = copy of x
+	ANDQ    DX, BX // BX = |x|
+	MOVQ    $Big, CX // if |x| >= 2**52 or IsNaN(x), return x
+	CMPQ    BX, CX
+	JAE     isBig_ceil
+	MOVQ	AX, X0 // X0 = x
+	MOVQ	DX, X2 // X2 = sign bit mask
+	CVTTSD2SQ	X0, AX
+	ANDNPD	X0, X2 // X2 = sign
+	CVTSQ2SD	AX, X1	// X1 = float(int(x))
+	CMPSD	X1, X0, 2 // compare LE; X0 = 0xffffffffffffffff or 0
+	ORPD	X2, X1 // if X1 = 0.0, incorporate sign
+	MOVSD	$1.0, X3
+	ANDNPD	X3, X0
+	ORPD	X2, X0 // if float(int(x)) <= x {X0 = 1} else {X0 = -0}
+	ADDSD	X1, X0
+	MOVSD	X0, ret+8(FP)
+	RET
+isBig_ceil:
+	MOVQ	AX, ret+8(FP)
+	RET
+
+// func archTrunc(x float64) float64
+TEXT ·archTrunc(SB),NOSPLIT,$0
+	MOVQ	x+0(FP), AX
+	MOVQ	$~(1<<63), DX // sign bit mask
+	MOVQ	AX, BX // BX = copy of x
+	ANDQ    DX, BX // BX = |x|
+	MOVQ    $Big, CX // if |x| >= 2**52 or IsNaN(x), return x
+	CMPQ    BX, CX
+	JAE     isBig_trunc
+	MOVQ	AX, X0
+	MOVQ	DX, X2 // X2 = sign bit mask
+	CVTTSD2SQ	X0, AX
+	ANDNPD	X0, X2 // X2 = sign
+	CVTSQ2SD	AX, X0 // X0 = float(int(x))
+	ORPD	X2, X0 // if X0 = 0.0, incorporate sign
+	MOVSD	X0, ret+8(FP)
+	RET
+isBig_trunc:
+	MOVQ    AX, ret+8(FP) // return x
+	RET
diff --git a/contrib/go/_std_1.18/src/math/floor_asm.go b/contrib/go/_std_1.18/src/math/floor_asm.go
new file mode 100644
index 0000000000..fb419d6da2
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/floor_asm.go
@@ -0,0 +1,19 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build 386 || amd64 || arm64 || ppc64 || ppc64le || s390x || wasm
+
+package math
+
+const haveArchFloor = true
+
+func archFloor(x float64) float64
+
+const haveArchCeil = true
+
+func archCeil(x float64) float64
+
+const haveArchTrunc = true
+
+func archTrunc(x float64) float64
diff --git a/contrib/go/_std_1.18/src/math/fma.go b/contrib/go/_std_1.18/src/math/fma.go
new file mode 100644
index 0000000000..ca0bf99f21
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/fma.go
@@ -0,0 +1,170 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+import "math/bits"
+
+func zero(x uint64) uint64 {
+	if x == 0 {
+		return 1
+	}
+	return 0
+	// branchless:
+	// return ((x>>1 | x&1) - 1) >> 63
+}
+
+func nonzero(x uint64) uint64 {
+	if x != 0 {
+		return 1
+	}
+	return 0
+	// branchless:
+	// return 1 - ((x>>1|x&1)-1)>>63
+}
+
+func shl(u1, u2 uint64, n uint) (r1, r2 uint64) {
+	r1 = u1<<n | u2>>(64-n) | u2<<(n-64)
+	r2 = u2 << n
+	return
+}
+
+func shr(u1, u2 uint64, n uint) (r1, r2 uint64) {
+	r2 = u2>>n | u1<<(64-n) | u1>>(n-64)
+	r1 = u1 >> n
+	return
+}
+
+// shrcompress compresses the bottom n+1 bits of the two-word
+// value into a single bit. the result is equal to the value
+// shifted to the right by n, except the result's 0th bit is
+// set to the bitwise OR of the bottom n+1 bits.
+func shrcompress(u1, u2 uint64, n uint) (r1, r2 uint64) {
+	// TODO: Performance here is really sensitive to the
+	// order/placement of these branches. n == 0 is common
+	// enough to be in the fast path. Perhaps more measurement
+	// needs to be done to find the optimal order/placement?
+	switch {
+	case n == 0:
+		return u1, u2
+	case n == 64:
+		return 0, u1 | nonzero(u2)
+	case n >= 128:
+		return 0, nonzero(u1 | u2)
+	case n < 64:
+		r1, r2 = shr(u1, u2, n)
+		r2 |= nonzero(u2 & (1<<n - 1))
+	case n < 128:
+		r1, r2 = shr(u1, u2, n)
+		r2 |= nonzero(u1&(1<<(n-64)-1) | u2)
+	}
+	return
+}
+
+func lz(u1, u2 uint64) (l int32) {
+	l = int32(bits.LeadingZeros64(u1))
+	if l == 64 {
+		l += int32(bits.LeadingZeros64(u2))
+	}
+	return l
+}
+
+// split splits b into sign, biased exponent, and mantissa.
+// It adds the implicit 1 bit to the mantissa for normal values,
+// and normalizes subnormal values.
+func split(b uint64) (sign uint32, exp int32, mantissa uint64) {
+	sign = uint32(b >> 63)
+	exp = int32(b>>52) & mask
+	mantissa = b & fracMask
+
+	if exp == 0 {
+		// Normalize value if subnormal.
+		shift := uint(bits.LeadingZeros64(mantissa) - 11)
+		mantissa <<= shift
+		exp = 1 - int32(shift)
+	} else {
+		// Add implicit 1 bit
+		mantissa |= 1 << 52
+	}
+	return
+}
+
+// FMA returns x * y + z, computed with only one rounding.
+// (That is, FMA returns the fused multiply-add of x, y, and z.)
+func FMA(x, y, z float64) float64 {
+	bx, by, bz := Float64bits(x), Float64bits(y), Float64bits(z)
+
+	// Inf or NaN or zero involved. At most one rounding will occur.
+	if x == 0.0 || y == 0.0 || z == 0.0 || bx&uvinf == uvinf || by&uvinf == uvinf {
+		return x*y + z
+	}
+	// Handle non-finite z separately. Evaluating x*y+z where
+	// x and y are finite, but z is infinite, should always result in z.
+	if bz&uvinf == uvinf {
+		return z
+	}
+
+	// Inputs are (sub)normal.
+	// Split x, y, z into sign, exponent, mantissa.
+	xs, xe, xm := split(bx)
+	ys, ye, ym := split(by)
+	zs, ze, zm := split(bz)
+
+	// Compute product p = x*y as sign, exponent, two-word mantissa.
+	// Start with exponent. "is normal" bit isn't subtracted yet.
+	pe := xe + ye - bias + 1
+
+	// pm1:pm2 is the double-word mantissa for the product p.
+	// Shift left to leave top bit in product. Effectively
+	// shifts the 106-bit product to the left by 21.
+	pm1, pm2 := bits.Mul64(xm<<10, ym<<11)
+	zm1, zm2 := zm<<10, uint64(0)
+	ps := xs ^ ys // product sign
+
+	// normalize to 62nd bit
+	is62zero := uint((^pm1 >> 62) & 1)
+	pm1, pm2 = shl(pm1, pm2, is62zero)
+	pe -= int32(is62zero)
+
+	// Swap addition operands so |p| >= |z|
+	if pe < ze || pe == ze && pm1 < zm1 {
+		ps, pe, pm1, pm2, zs, ze, zm1, zm2 = zs, ze, zm1, zm2, ps, pe, pm1, pm2
+	}
+
+	// Align significands
+	zm1, zm2 = shrcompress(zm1, zm2, uint(pe-ze))
+
+	// Compute resulting significands, normalizing if necessary.
+	var m, c uint64
+	if ps == zs {
+		// Adding (pm1:pm2) + (zm1:zm2)
+		pm2, c = bits.Add64(pm2, zm2, 0)
+		pm1, _ = bits.Add64(pm1, zm1, c)
+		pe -= int32(^pm1 >> 63)
+		pm1, m = shrcompress(pm1, pm2, uint(64+pm1>>63))
+	} else {
+		// Subtracting (pm1:pm2) - (zm1:zm2)
+		// TODO: should we special-case cancellation?
+		pm2, c = bits.Sub64(pm2, zm2, 0)
+		pm1, _ = bits.Sub64(pm1, zm1, c)
+		nz := lz(pm1, pm2)
+		pe -= nz
+		m, pm2 = shl(pm1, pm2, uint(nz-1))
+		m |= nonzero(pm2)
+	}
+
+	// Round and break ties to even
+	if pe > 1022+bias || pe == 1022+bias && (m+1<<9)>>63 == 1 {
+		// rounded value overflows exponent range
+		return Float64frombits(uint64(ps)<<63 | uvinf)
+	}
+	if pe < 0 {
+		n := uint(-pe)
+		m = m>>n | nonzero(m&(1<<n-1))
+		pe = 0
+	}
+	m = ((m + 1<<9) >> 10) & ^zero((m&(1<<10-1))^1<<9)
+	pe &= -int32(nonzero(m))
+	return Float64frombits(uint64(ps)<<63 + uint64(pe)<<52 + m)
+}
diff --git a/contrib/go/_std_1.18/src/math/frexp.go b/contrib/go/_std_1.18/src/math/frexp.go
new file mode 100644
index 0000000000..3c8a909ed0
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/frexp.go
@@ -0,0 +1,38 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Frexp breaks f into a normalized fraction
+// and an integral power of two.
+// It returns frac and exp satisfying f == frac × 2**exp,
+// with the absolute value of frac in the interval [½, 1).
+//
+// Special cases are:
+//	Frexp(±0) = ±0, 0
+//	Frexp(±Inf) = ±Inf, 0
+//	Frexp(NaN) = NaN, 0
+func Frexp(f float64) (frac float64, exp int) {
+	if haveArchFrexp {
+		return archFrexp(f)
+	}
+	return frexp(f)
+}
+
+func frexp(f float64) (frac float64, exp int) {
+	// special cases
+	switch {
+	case f == 0:
+		return f, 0 // correctly return -0
+	case IsInf(f, 0) || IsNaN(f):
+		return f, 0
+	}
+	f, exp = normalize(f)
+	x := Float64bits(f)
+	exp += int((x>>shift)&mask) - bias + 1
+	x &^= mask << shift
+	x |= (-1 + bias) << shift
+	frac = Float64frombits(x)
+	return
+}
diff --git a/contrib/go/_std_1.18/src/math/gamma.go b/contrib/go/_std_1.18/src/math/gamma.go
new file mode 100644
index 0000000000..cc9e869496
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/gamma.go
@@ -0,0 +1,221 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// The original C code, the long comment, and the constants
+// below are from http://netlib.sandia.gov/cephes/cprob/gamma.c.
+// The go code is a simplified version of the original C.
+//
+//      tgamma.c
+//
+//      Gamma function
+//
+// SYNOPSIS:
+//
+// double x, y, tgamma();
+// extern int signgam;
+//
+// y = tgamma( x );
+//
+// DESCRIPTION:
+//
+// Returns gamma function of the argument. The result is
+// correctly signed, and the sign (+1 or -1) is also
+// returned in a global (extern) variable named signgam.
+// This variable is also filled in by the logarithmic gamma
+// function lgamma().
+//
+// Arguments |x| <= 34 are reduced by recurrence and the function
+// approximated by a rational function of degree 6/7 in the
+// interval (2,3).  Large arguments are handled by Stirling's
+// formula. Large negative arguments are made positive using
+// a reflection formula.
+//
+// ACCURACY:
+//
+//                      Relative error:
+// arithmetic   domain     # trials      peak         rms
+//    DEC      -34, 34      10000       1.3e-16     2.5e-17
+//    IEEE    -170,-33      20000       2.3e-15     3.3e-16
+//    IEEE     -33,  33     20000       9.4e-16     2.2e-16
+//    IEEE      33, 171.6   20000       2.3e-15     3.2e-16
+//
+// Error for arguments outside the test range will be larger
+// owing to error amplification by the exponential function.
+//
+// Cephes Math Library Release 2.8:  June, 2000
+// Copyright 1984, 1987, 1989, 1992, 2000 by Stephen L. Moshier
+//
+// The readme file at http://netlib.sandia.gov/cephes/ says:
+//    Some software in this archive may be from the book _Methods and
+// Programs for Mathematical Functions_ (Prentice-Hall or Simon & Schuster
+// International, 1989) or from the Cephes Mathematical Library, a
+// commercial product. In either event, it is copyrighted by the author.
+// What you see here may be used freely but it comes with no support or
+// guarantee.
+//
+//   The two known misprints in the book are repaired here in the
+// source listings for the gamma function and the incomplete beta
+// integral.
+//
+//   Stephen L. Moshier
+//   moshier@na-net.ornl.gov
+
+var _gamP = [...]float64{
+	1.60119522476751861407e-04,
+	1.19135147006586384913e-03,
+	1.04213797561761569935e-02,
+	4.76367800457137231464e-02,
+	2.07448227648435975150e-01,
+	4.94214826801497100753e-01,
+	9.99999999999999996796e-01,
+}
+var _gamQ = [...]float64{
+	-2.31581873324120129819e-05,
+	5.39605580493303397842e-04,
+	-4.45641913851797240494e-03,
+	1.18139785222060435552e-02,
+	3.58236398605498653373e-02,
+	-2.34591795718243348568e-01,
+	7.14304917030273074085e-02,
+	1.00000000000000000320e+00,
+}
+var _gamS = [...]float64{
+	7.87311395793093628397e-04,
+	-2.29549961613378126380e-04,
+	-2.68132617805781232825e-03,
+	3.47222221605458667310e-03,
+	8.33333333333482257126e-02,
+}
+
+// Gamma function computed by Stirling's formula.
+// The pair of results must be multiplied together to get the actual answer.
+// The multiplication is left to the caller so that, if careful, the caller can avoid
+// infinity for 172 <= x <= 180.
+// The polynomial is valid for 33 <= x <= 172; larger values are only used
+// in reciprocal and produce denormalized floats. The lower precision there
+// masks any imprecision in the polynomial.
+func stirling(x float64) (float64, float64) {
+	if x > 200 {
+		return Inf(1), 1
+	}
+	const (
+		SqrtTwoPi   = 2.506628274631000502417
+		MaxStirling = 143.01608
+	)
+	w := 1 / x
+	w = 1 + w*((((_gamS[0]*w+_gamS[1])*w+_gamS[2])*w+_gamS[3])*w+_gamS[4])
+	y1 := Exp(x)
+	y2 := 1.0
+	if x > MaxStirling { // avoid Pow() overflow
+		v := Pow(x, 0.5*x-0.25)
+		y1, y2 = v, v/y1
+	} else {
+		y1 = Pow(x, x-0.5) / y1
+	}
+	return y1, SqrtTwoPi * w * y2
+}
+
+// Gamma returns the Gamma function of x.
+//
+// Special cases are:
+//	Gamma(+Inf) = +Inf
+//	Gamma(+0) = +Inf
+//	Gamma(-0) = -Inf
+//	Gamma(x) = NaN for integer x < 0
+//	Gamma(-Inf) = NaN
+//	Gamma(NaN) = NaN
+func Gamma(x float64) float64 {
+	const Euler = 0.57721566490153286060651209008240243104215933593992 // A001620
+	// special cases
+	switch {
+	case isNegInt(x) || IsInf(x, -1) || IsNaN(x):
+		return NaN()
+	case IsInf(x, 1):
+		return Inf(1)
+	case x == 0:
+		if Signbit(x) {
+			return Inf(-1)
+		}
+		return Inf(1)
+	}
+	q := Abs(x)
+	p := Floor(q)
+	if q > 33 {
+		if x >= 0 {
+			y1, y2 := stirling(x)
+			return y1 * y2
+		}
+		// Note: x is negative but (checked above) not a negative integer,
+		// so x must be small enough to be in range for conversion to int64.
+		// If |x| were >= 2⁶³ it would have to be an integer.
+		signgam := 1
+		if ip := int64(p); ip&1 == 0 {
+			signgam = -1
+		}
+		z := q - p
+		if z > 0.5 {
+			p = p + 1
+			z = q - p
+		}
+		z = q * Sin(Pi*z)
+		if z == 0 {
+			return Inf(signgam)
+		}
+		sq1, sq2 := stirling(q)
+		absz := Abs(z)
+		d := absz * sq1 * sq2
+		if IsInf(d, 0) {
+			z = Pi / absz / sq1 / sq2
+		} else {
+			z = Pi / d
+		}
+		return float64(signgam) * z
+	}
+
+	// Reduce argument
+	z := 1.0
+	for x >= 3 {
+		x = x - 1
+		z = z * x
+	}
+	for x < 0 {
+		if x > -1e-09 {
+			goto small
+		}
+		z = z / x
+		x = x + 1
+	}
+	for x < 2 {
+		if x < 1e-09 {
+			goto small
+		}
+		z = z / x
+		x = x + 1
+	}
+
+	if x == 2 {
+		return z
+	}
+
+	x = x - 2
+	p = (((((x*_gamP[0]+_gamP[1])*x+_gamP[2])*x+_gamP[3])*x+_gamP[4])*x+_gamP[5])*x + _gamP[6]
+	q = ((((((x*_gamQ[0]+_gamQ[1])*x+_gamQ[2])*x+_gamQ[3])*x+_gamQ[4])*x+_gamQ[5])*x+_gamQ[6])*x + _gamQ[7]
+	return z * p / q
+
+small:
+	if x == 0 {
+		return Inf(1)
+	}
+	return z / ((1 + Euler*x) * x)
+}
+
+func isNegInt(x float64) bool {
+	if x < 0 {
+		_, xf := Modf(x)
+		return xf == 0
+	}
+	return false
+}
diff --git a/contrib/go/_std_1.18/src/math/hypot.go b/contrib/go/_std_1.18/src/math/hypot.go
new file mode 100644
index 0000000000..12af17766d
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/hypot.go
@@ -0,0 +1,43 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Hypot -- sqrt(p*p + q*q), but overflows only if the result does.
+*/
+
+// Hypot returns Sqrt(p*p + q*q), taking care to avoid
+// unnecessary overflow and underflow.
+//
+// Special cases are:
+//	Hypot(±Inf, q) = +Inf
+//	Hypot(p, ±Inf) = +Inf
+//	Hypot(NaN, q) = NaN
+//	Hypot(p, NaN) = NaN
+func Hypot(p, q float64) float64 {
+	if haveArchHypot {
+		return archHypot(p, q)
+	}
+	return hypot(p, q)
+}
+
+func hypot(p, q float64) float64 {
+	// special cases
+	switch {
+	case IsInf(p, 0) || IsInf(q, 0):
+		return Inf(1)
+	case IsNaN(p) || IsNaN(q):
+		return NaN()
+	}
+	p, q = Abs(p), Abs(q)
+	if p < q {
+		p, q = q, p
+	}
+	if p == 0 {
+		return 0
+	}
+	q = q / p
+	return p * Sqrt(1+q*q)
+}
diff --git a/contrib/go/_std_1.18/src/math/hypot_amd64.s b/contrib/go/_std_1.18/src/math/hypot_amd64.s
new file mode 100644
index 0000000000..fe326c9281
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/hypot_amd64.s
@@ -0,0 +1,52 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "textflag.h"
+
+#define PosInf 0x7FF0000000000000
+#define NaN 0x7FF8000000000001
+
+// func archHypot(p, q float64) float64
+TEXT ·archHypot(SB),NOSPLIT,$0
+	// test bits for special cases
+	MOVQ    p+0(FP), BX
+	MOVQ    $~(1<<63), AX
+	ANDQ    AX, BX // p = |p|
+	MOVQ    q+8(FP), CX
+	ANDQ    AX, CX // q = |q|
+	MOVQ    $PosInf, AX
+	CMPQ    AX, BX
+	JLE     isInfOrNaN
+	CMPQ    AX, CX
+	JLE     isInfOrNaN
+	// hypot = max * sqrt(1 + (min/max)**2)
+	MOVQ    BX, X0
+	MOVQ    CX, X1
+	ORQ     CX, BX
+	JEQ     isZero
+	MOVAPD  X0, X2
+	MAXSD   X1, X0
+	MINSD   X2, X1
+	DIVSD   X0, X1
+	MULSD   X1, X1
+	ADDSD   $1.0, X1
+	SQRTSD  X1, X1
+	MULSD   X1, X0
+	MOVSD   X0, ret+16(FP)
+	RET
+isInfOrNaN:
+	CMPQ    AX, BX
+	JEQ     isInf
+	CMPQ    AX, CX
+	JEQ     isInf
+	MOVQ    $NaN, AX
+	MOVQ    AX, ret+16(FP) // return NaN
+	RET
+isInf:
+	MOVQ    AX, ret+16(FP) // return +Inf
+	RET
+isZero:
+	MOVQ    $0, AX
+	MOVQ    AX, ret+16(FP) // return 0
+	RET
diff --git a/contrib/go/_std_1.18/src/math/hypot_asm.go b/contrib/go/_std_1.18/src/math/hypot_asm.go
new file mode 100644
index 0000000000..852691037f
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/hypot_asm.go
@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build 386 || amd64
+
+package math
+
+const haveArchHypot = true
+
+func archHypot(p, q float64) float64
diff --git a/contrib/go/_std_1.18/src/math/j0.go b/contrib/go/_std_1.18/src/math/j0.go
new file mode 100644
index 0000000000..cb5f07bca6
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/j0.go
@@ -0,0 +1,427 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Bessel function of the first and second kinds of order zero.
+*/
+
+// The original C code and the long comment below are
+// from FreeBSD's /usr/src/lib/msun/src/e_j0.c and
+// came with this notice. The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+// __ieee754_j0(x), __ieee754_y0(x)
+// Bessel function of the first and second kinds of order zero.
+// Method -- j0(x):
+//      1. For tiny x, we use j0(x) = 1 - x**2/4 + x**4/64 - ...
+//      2. Reduce x to |x| since j0(x)=j0(-x),  and
+//         for x in (0,2)
+//              j0(x) = 1-z/4+ z**2*R0/S0,  where z = x*x;
+//         (precision:  |j0-1+z/4-z**2R0/S0 |<2**-63.67 )
+//         for x in (2,inf)
+//              j0(x) = sqrt(2/(pi*x))*(p0(x)*cos(x0)-q0(x)*sin(x0))
+//         where x0 = x-pi/4. It is better to compute sin(x0),cos(x0)
+//         as follow:
+//              cos(x0) = cos(x)cos(pi/4)+sin(x)sin(pi/4)
+//                      = 1/sqrt(2) * (cos(x) + sin(x))
+//              sin(x0) = sin(x)cos(pi/4)-cos(x)sin(pi/4)
+//                      = 1/sqrt(2) * (sin(x) - cos(x))
+//         (To avoid cancellation, use
+//              sin(x) +- cos(x) = -cos(2x)/(sin(x) -+ cos(x))
+//         to compute the worse one.)
+//
+//      3 Special cases
+//              j0(nan)= nan
+//              j0(0) = 1
+//              j0(inf) = 0
+//
+// Method -- y0(x):
+//      1. For x<2.
+//         Since
+//              y0(x) = 2/pi*(j0(x)*(ln(x/2)+Euler) + x**2/4 - ...)
+//         therefore y0(x)-2/pi*j0(x)*ln(x) is an even function.
+//         We use the following function to approximate y0,
+//              y0(x) = U(z)/V(z) + (2/pi)*(j0(x)*ln(x)), z= x**2
+//         where
+//              U(z) = u00 + u01*z + ... + u06*z**6
+//              V(z) = 1  + v01*z + ... + v04*z**4
+//         with absolute approximation error bounded by 2**-72.
+//         Note: For tiny x, U/V = u0 and j0(x)~1, hence
+//              y0(tiny) = u0 + (2/pi)*ln(tiny), (choose tiny<2**-27)
+//      2. For x>=2.
+//              y0(x) = sqrt(2/(pi*x))*(p0(x)*cos(x0)+q0(x)*sin(x0))
+//         where x0 = x-pi/4. It is better to compute sin(x0),cos(x0)
+//         by the method mentioned above.
+//      3. Special cases: y0(0)=-inf, y0(x<0)=NaN, y0(inf)=0.
+//
+
+// J0 returns the order-zero Bessel function of the first kind.
+//
+// Special cases are:
+//	J0(±Inf) = 0
+//	J0(0) = 1
+//	J0(NaN) = NaN
+func J0(x float64) float64 {
+	const (
+		Huge   = 1e300
+		TwoM27 = 1.0 / (1 << 27) // 2**-27 0x3e40000000000000
+		TwoM13 = 1.0 / (1 << 13) // 2**-13 0x3f20000000000000
+		Two129 = 1 << 129        // 2**129 0x4800000000000000
+		// R0/S0 on [0, 2]
+		R02 = 1.56249999999999947958e-02  // 0x3F8FFFFFFFFFFFFD
+		R03 = -1.89979294238854721751e-04 // 0xBF28E6A5B61AC6E9
+		R04 = 1.82954049532700665670e-06  // 0x3EBEB1D10C503919
+		R05 = -4.61832688532103189199e-09 // 0xBE33D5E773D63FCE
+		S01 = 1.56191029464890010492e-02  // 0x3F8FFCE882C8C2A4
+		S02 = 1.16926784663337450260e-04  // 0x3F1EA6D2DD57DBF4
+		S03 = 5.13546550207318111446e-07  // 0x3EA13B54CE84D5A9
+		S04 = 1.16614003333790000205e-09  // 0x3E1408BCF4745D8F
+	)
+	// special cases
+	switch {
+	case IsNaN(x):
+		return x
+	case IsInf(x, 0):
+		return 0
+	case x == 0:
+		return 1
+	}
+
+	x = Abs(x)
+	if x >= 2 {
+		s, c := Sincos(x)
+		ss := s - c
+		cc := s + c
+
+		// make sure x+x does not overflow
+		if x < MaxFloat64/2 {
+			z := -Cos(x + x)
+			if s*c < 0 {
+				cc = z / ss
+			} else {
+				ss = z / cc
+			}
+		}
+
+		// j0(x) = 1/sqrt(pi) * (P(0,x)*cc - Q(0,x)*ss) / sqrt(x)
+		// y0(x) = 1/sqrt(pi) * (P(0,x)*ss + Q(0,x)*cc) / sqrt(x)
+
+		var z float64
+		if x > Two129 { // |x| > ~6.8056e+38
+			z = (1 / SqrtPi) * cc / Sqrt(x)
+		} else {
+			u := pzero(x)
+			v := qzero(x)
+			z = (1 / SqrtPi) * (u*cc - v*ss) / Sqrt(x)
+		}
+		return z // |x| >= 2.0
+	}
+	if x < TwoM13 { // |x| < ~1.2207e-4
+		if x < TwoM27 {
+			return 1 // |x| < ~7.4506e-9
+		}
+		return 1 - 0.25*x*x // ~7.4506e-9 < |x| < ~1.2207e-4
+	}
+	z := x * x
+	r := z * (R02 + z*(R03+z*(R04+z*R05)))
+	s := 1 + z*(S01+z*(S02+z*(S03+z*S04)))
+	if x < 1 {
+		return 1 + z*(-0.25+(r/s)) // |x| < 1.00
+	}
+	u := 0.5 * x
+	return (1+u)*(1-u) + z*(r/s) // 1.0 < |x| < 2.0
+}
+
+// Y0 returns the order-zero Bessel function of the second kind.
+//
+// Special cases are:
+//	Y0(+Inf) = 0
+//	Y0(0) = -Inf
+//	Y0(x < 0) = NaN
+//	Y0(NaN) = NaN
+func Y0(x float64) float64 {
+	const (
+		TwoM27 = 1.0 / (1 << 27)             // 2**-27 0x3e40000000000000
+		Two129 = 1 << 129                    // 2**129 0x4800000000000000
+		U00    = -7.38042951086872317523e-02 // 0xBFB2E4D699CBD01F
+		U01    = 1.76666452509181115538e-01  // 0x3FC69D019DE9E3FC
+		U02    = -1.38185671945596898896e-02 // 0xBF8C4CE8B16CFA97
+		U03    = 3.47453432093683650238e-04  // 0x3F36C54D20B29B6B
+		U04    = -3.81407053724364161125e-06 // 0xBECFFEA773D25CAD
+		U05    = 1.95590137035022920206e-08  // 0x3E5500573B4EABD4
+		U06    = -3.98205194132103398453e-11 // 0xBDC5E43D693FB3C8
+		V01    = 1.27304834834123699328e-02  // 0x3F8A127091C9C71A
+		V02    = 7.60068627350353253702e-05  // 0x3F13ECBBF578C6C1
+		V03    = 2.59150851840457805467e-07  // 0x3E91642D7FF202FD
+		V04    = 4.41110311332675467403e-10  // 0x3DFE50183BD6D9EF
+	)
+	// special cases
+	switch {
+	case x < 0 || IsNaN(x):
+		return NaN()
+	case IsInf(x, 1):
+		return 0
+	case x == 0:
+		return Inf(-1)
+	}
+
+	if x >= 2 { // |x| >= 2.0
+
+		// y0(x) = sqrt(2/(pi*x))*(p0(x)*sin(x0)+q0(x)*cos(x0))
+		//     where x0 = x-pi/4
+		// Better formula:
+		//     cos(x0) = cos(x)cos(pi/4)+sin(x)sin(pi/4)
+		//             =  1/sqrt(2) * (sin(x) + cos(x))
+		//     sin(x0) = sin(x)cos(3pi/4)-cos(x)sin(3pi/4)
+		//             =  1/sqrt(2) * (sin(x) - cos(x))
+		// To avoid cancellation, use
+		//     sin(x) +- cos(x) = -cos(2x)/(sin(x) -+ cos(x))
+		// to compute the worse one.
+
+		s, c := Sincos(x)
+		ss := s - c
+		cc := s + c
+
+		// j0(x) = 1/sqrt(pi) * (P(0,x)*cc - Q(0,x)*ss) / sqrt(x)
+		// y0(x) = 1/sqrt(pi) * (P(0,x)*ss + Q(0,x)*cc) / sqrt(x)
+
+		// make sure x+x does not overflow
+		if x < MaxFloat64/2 {
+			z := -Cos(x + x)
+			if s*c < 0 {
+				cc = z / ss
+			} else {
+				ss = z / cc
+			}
+		}
+		var z float64
+		if x > Two129 { // |x| > ~6.8056e+38
+			z = (1 / SqrtPi) * ss / Sqrt(x)
+		} else {
+			u := pzero(x)
+			v := qzero(x)
+			z = (1 / SqrtPi) * (u*ss + v*cc) / Sqrt(x)
+		}
+		return z // |x| >= 2.0
+	}
+	if x <= TwoM27 {
+		return U00 + (2/Pi)*Log(x) // |x| < ~7.4506e-9
+	}
+	z := x * x
+	u := U00 + z*(U01+z*(U02+z*(U03+z*(U04+z*(U05+z*U06)))))
+	v := 1 + z*(V01+z*(V02+z*(V03+z*V04)))
+	return u/v + (2/Pi)*J0(x)*Log(x) // ~7.4506e-9 < |x| < 2.0
+}
+
+// The asymptotic expansions of pzero is
+//      1 - 9/128 s**2 + 11025/98304 s**4 - ..., where s = 1/x.
+// For x >= 2, We approximate pzero by
+// 	pzero(x) = 1 + (R/S)
+// where  R = pR0 + pR1*s**2 + pR2*s**4 + ... + pR5*s**10
+// 	  S = 1 + pS0*s**2 + ... + pS4*s**10
+// and
+//      | pzero(x)-1-R/S | <= 2  ** ( -60.26)
+
+// for x in [inf, 8]=1/[0,0.125]
+var p0R8 = [6]float64{
+	0.00000000000000000000e+00,  // 0x0000000000000000
+	-7.03124999999900357484e-02, // 0xBFB1FFFFFFFFFD32
+	-8.08167041275349795626e+00, // 0xC02029D0B44FA779
+	-2.57063105679704847262e+02, // 0xC07011027B19E863
+	-2.48521641009428822144e+03, // 0xC0A36A6ECD4DCAFC
+	-5.25304380490729545272e+03, // 0xC0B4850B36CC643D
+}
+var p0S8 = [5]float64{
+	1.16534364619668181717e+02, // 0x405D223307A96751
+	3.83374475364121826715e+03, // 0x40ADF37D50596938
+	4.05978572648472545552e+04, // 0x40E3D2BB6EB6B05F
+	1.16752972564375915681e+05, // 0x40FC810F8F9FA9BD
+	4.76277284146730962675e+04, // 0x40E741774F2C49DC
+}
+
+// for x in [8,4.5454]=1/[0.125,0.22001]
+var p0R5 = [6]float64{
+	-1.14125464691894502584e-11, // 0xBDA918B147E495CC
+	-7.03124940873599280078e-02, // 0xBFB1FFFFE69AFBC6
+	-4.15961064470587782438e+00, // 0xC010A370F90C6BBF
+	-6.76747652265167261021e+01, // 0xC050EB2F5A7D1783
+	-3.31231299649172967747e+02, // 0xC074B3B36742CC63
+	-3.46433388365604912451e+02, // 0xC075A6EF28A38BD7
+}
+var p0S5 = [5]float64{
+	6.07539382692300335975e+01, // 0x404E60810C98C5DE
+	1.05125230595704579173e+03, // 0x40906D025C7E2864
+	5.97897094333855784498e+03, // 0x40B75AF88FBE1D60
+	9.62544514357774460223e+03, // 0x40C2CCB8FA76FA38
+	2.40605815922939109441e+03, // 0x40A2CC1DC70BE864
+}
+
+// for x in [4.547,2.8571]=1/[0.2199,0.35001]
+var p0R3 = [6]float64{
+	-2.54704601771951915620e-09, // 0xBE25E1036FE1AA86
+	-7.03119616381481654654e-02, // 0xBFB1FFF6F7C0E24B
+	-2.40903221549529611423e+00, // 0xC00345B2AEA48074
+	-2.19659774734883086467e+01, // 0xC035F74A4CB94E14
+	-5.80791704701737572236e+01, // 0xC04D0A22420A1A45
+	-3.14479470594888503854e+01, // 0xC03F72ACA892D80F
+}
+var p0S3 = [5]float64{
+	3.58560338055209726349e+01, // 0x4041ED9284077DD3
+	3.61513983050303863820e+02, // 0x40769839464A7C0E
+	1.19360783792111533330e+03, // 0x4092A66E6D1061D6
+	1.12799679856907414432e+03, // 0x40919FFCB8C39B7E
+	1.73580930813335754692e+02, // 0x4065B296FC379081
+}
+
+// for x in [2.8570,2]=1/[0.3499,0.5]
+var p0R2 = [6]float64{
+	-8.87534333032526411254e-08, // 0xBE77D316E927026D
+	-7.03030995483624743247e-02, // 0xBFB1FF62495E1E42
+	-1.45073846780952986357e+00, // 0xBFF736398A24A843
+	-7.63569613823527770791e+00, // 0xC01E8AF3EDAFA7F3
+	-1.11931668860356747786e+01, // 0xC02662E6C5246303
+	-3.23364579351335335033e+00, // 0xC009DE81AF8FE70F
+}
+var p0S2 = [5]float64{
+	2.22202997532088808441e+01, // 0x40363865908B5959
+	1.36206794218215208048e+02, // 0x4061069E0EE8878F
+	2.70470278658083486789e+02, // 0x4070E78642EA079B
+	1.53875394208320329881e+02, // 0x40633C033AB6FAFF
+	1.46576176948256193810e+01, // 0x402D50B344391809
+}
+
+func pzero(x float64) float64 {
+	var p *[6]float64
+	var q *[5]float64
+	if x >= 8 {
+		p = &p0R8
+		q = &p0S8
+	} else if x >= 4.5454 {
+		p = &p0R5
+		q = &p0S5
+	} else if x >= 2.8571 {
+		p = &p0R3
+		q = &p0S3
+	} else if x >= 2 {
+		p = &p0R2
+		q = &p0S2
+	}
+	z := 1 / (x * x)
+	r := p[0] + z*(p[1]+z*(p[2]+z*(p[3]+z*(p[4]+z*p[5]))))
+	s := 1 + z*(q[0]+z*(q[1]+z*(q[2]+z*(q[3]+z*q[4]))))
+	return 1 + r/s
+}
+
+// For x >= 8, the asymptotic expansions of qzero is
+//      -1/8 s + 75/1024 s**3 - ..., where s = 1/x.
+// We approximate pzero by
+//      qzero(x) = s*(-1.25 + (R/S))
+// where R = qR0 + qR1*s**2 + qR2*s**4 + ... + qR5*s**10
+//       S = 1 + qS0*s**2 + ... + qS5*s**12
+// and
+//      | qzero(x)/s +1.25-R/S | <= 2**(-61.22)
+
+// for x in [inf, 8]=1/[0,0.125]
+var q0R8 = [6]float64{
+	0.00000000000000000000e+00, // 0x0000000000000000
+	7.32421874999935051953e-02, // 0x3FB2BFFFFFFFFE2C
+	1.17682064682252693899e+01, // 0x402789525BB334D6
+	5.57673380256401856059e+02, // 0x40816D6315301825
+	8.85919720756468632317e+03, // 0x40C14D993E18F46D
+	3.70146267776887834771e+04, // 0x40E212D40E901566
+}
+var q0S8 = [6]float64{
+	1.63776026895689824414e+02,  // 0x406478D5365B39BC
+	8.09834494656449805916e+03,  // 0x40BFA2584E6B0563
+	1.42538291419120476348e+05,  // 0x4101665254D38C3F
+	8.03309257119514397345e+05,  // 0x412883DA83A52B43
+	8.40501579819060512818e+05,  // 0x4129A66B28DE0B3D
+	-3.43899293537866615225e+05, // 0xC114FD6D2C9530C5
+}
+
+// for x in [8,4.5454]=1/[0.125,0.22001]
+var q0R5 = [6]float64{
+	1.84085963594515531381e-11, // 0x3DB43D8F29CC8CD9
+	7.32421766612684765896e-02, // 0x3FB2BFFFD172B04C
+	5.83563508962056953777e+00, // 0x401757B0B9953DD3
+	1.35111577286449829671e+02, // 0x4060E3920A8788E9
+	1.02724376596164097464e+03, // 0x40900CF99DC8C481
+	1.98997785864605384631e+03, // 0x409F17E953C6E3A6
+}
+var q0S5 = [6]float64{
+	8.27766102236537761883e+01,  // 0x4054B1B3FB5E1543
+	2.07781416421392987104e+03,  // 0x40A03BA0DA21C0CE
+	1.88472887785718085070e+04,  // 0x40D267D27B591E6D
+	5.67511122894947329769e+04,  // 0x40EBB5E397E02372
+	3.59767538425114471465e+04,  // 0x40E191181F7A54A0
+	-5.35434275601944773371e+03, // 0xC0B4EA57BEDBC609
+}
+
+// for x in [4.547,2.8571]=1/[0.2199,0.35001]
+var q0R3 = [6]float64{
+	4.37741014089738620906e-09, // 0x3E32CD036ADECB82
+	7.32411180042911447163e-02, // 0x3FB2BFEE0E8D0842
+	3.34423137516170720929e+00, // 0x400AC0FC61149CF5
+	4.26218440745412650017e+01, // 0x40454F98962DAEDD
+	1.70808091340565596283e+02, // 0x406559DBE25EFD1F
+	1.66733948696651168575e+02, // 0x4064D77C81FA21E0
+}
+var q0S3 = [6]float64{
+	4.87588729724587182091e+01,  // 0x40486122BFE343A6
+	7.09689221056606015736e+02,  // 0x40862D8386544EB3
+	3.70414822620111362994e+03,  // 0x40ACF04BE44DFC63
+	6.46042516752568917582e+03,  // 0x40B93C6CD7C76A28
+	2.51633368920368957333e+03,  // 0x40A3A8AAD94FB1C0
+	-1.49247451836156386662e+02, // 0xC062A7EB201CF40F
+}
+
+// for x in [2.8570,2]=1/[0.3499,0.5]
+var q0R2 = [6]float64{
+	1.50444444886983272379e-07, // 0x3E84313B54F76BDB
+	7.32234265963079278272e-02, // 0x3FB2BEC53E883E34
+	1.99819174093815998816e+00, // 0x3FFFF897E727779C
+	1.44956029347885735348e+01, // 0x402CFDBFAAF96FE5
+	3.16662317504781540833e+01, // 0x403FAA8E29FBDC4A
+	1.62527075710929267416e+01, // 0x403040B171814BB4
+}
+var q0S2 = [6]float64{
+	3.03655848355219184498e+01,  // 0x403E5D96F7C07AED
+	2.69348118608049844624e+02,  // 0x4070D591E4D14B40
+	8.44783757595320139444e+02,  // 0x408A664522B3BF22
+	8.82935845112488550512e+02,  // 0x408B977C9C5CC214
+	2.12666388511798828631e+02,  // 0x406A95530E001365
+	-5.31095493882666946917e+00, // 0xC0153E6AF8B32931
+}
+
+func qzero(x float64) float64 {
+	var p, q *[6]float64
+	if x >= 8 {
+		p = &q0R8
+		q = &q0S8
+	} else if x >= 4.5454 {
+		p = &q0R5
+		q = &q0S5
+	} else if x >= 2.8571 {
+		p = &q0R3
+		q = &q0S3
+	} else if x >= 2 {
+		p = &q0R2
+		q = &q0S2
+	}
+	z := 1 / (x * x)
+	r := p[0] + z*(p[1]+z*(p[2]+z*(p[3]+z*(p[4]+z*p[5]))))
+	s := 1 + z*(q[0]+z*(q[1]+z*(q[2]+z*(q[3]+z*(q[4]+z*q[5])))))
+	return (-0.125 + r/s) / x
+}
diff --git a/contrib/go/_std_1.18/src/math/j1.go b/contrib/go/_std_1.18/src/math/j1.go
new file mode 100644
index 0000000000..7c7d279730
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/j1.go
@@ -0,0 +1,422 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Bessel function of the first and second kinds of order one.
+*/
+
+// The original C code and the long comment below are
+// from FreeBSD's /usr/src/lib/msun/src/e_j1.c and
+// came with this notice. The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+// __ieee754_j1(x), __ieee754_y1(x)
+// Bessel function of the first and second kinds of order one.
+// Method -- j1(x):
+//      1. For tiny x, we use j1(x) = x/2 - x**3/16 + x**5/384 - ...
+//      2. Reduce x to |x| since j1(x)=-j1(-x),  and
+//         for x in (0,2)
+//              j1(x) = x/2 + x*z*R0/S0,  where z = x*x;
+//         (precision:  |j1/x - 1/2 - R0/S0 |<2**-61.51 )
+//         for x in (2,inf)
+//              j1(x) = sqrt(2/(pi*x))*(p1(x)*cos(x1)-q1(x)*sin(x1))
+//              y1(x) = sqrt(2/(pi*x))*(p1(x)*sin(x1)+q1(x)*cos(x1))
+//         where x1 = x-3*pi/4. It is better to compute sin(x1),cos(x1)
+//         as follow:
+//              cos(x1) =  cos(x)cos(3pi/4)+sin(x)sin(3pi/4)
+//                      =  1/sqrt(2) * (sin(x) - cos(x))
+//              sin(x1) =  sin(x)cos(3pi/4)-cos(x)sin(3pi/4)
+//                      = -1/sqrt(2) * (sin(x) + cos(x))
+//         (To avoid cancellation, use
+//              sin(x) +- cos(x) = -cos(2x)/(sin(x) -+ cos(x))
+//         to compute the worse one.)
+//
+//      3 Special cases
+//              j1(nan)= nan
+//              j1(0) = 0
+//              j1(inf) = 0
+//
+// Method -- y1(x):
+//      1. screen out x<=0 cases: y1(0)=-inf, y1(x<0)=NaN
+//      2. For x<2.
+//         Since
+//              y1(x) = 2/pi*(j1(x)*(ln(x/2)+Euler)-1/x-x/2+5/64*x**3-...)
+//         therefore y1(x)-2/pi*j1(x)*ln(x)-1/x is an odd function.
+//         We use the following function to approximate y1,
+//              y1(x) = x*U(z)/V(z) + (2/pi)*(j1(x)*ln(x)-1/x), z= x**2
+//         where for x in [0,2] (abs err less than 2**-65.89)
+//              U(z) = U0[0] + U0[1]*z + ... + U0[4]*z**4
+//              V(z) = 1  + v0[0]*z + ... + v0[4]*z**5
+//         Note: For tiny x, 1/x dominate y1 and hence
+//              y1(tiny) = -2/pi/tiny, (choose tiny<2**-54)
+//      3. For x>=2.
+//               y1(x) = sqrt(2/(pi*x))*(p1(x)*sin(x1)+q1(x)*cos(x1))
+//         where x1 = x-3*pi/4. It is better to compute sin(x1),cos(x1)
+//         by method mentioned above.
+
+// J1 returns the order-one Bessel function of the first kind.
+//
+// Special cases are:
+//	J1(±Inf) = 0
+//	J1(NaN) = NaN
+func J1(x float64) float64 {
+	const (
+		TwoM27 = 1.0 / (1 << 27) // 2**-27 0x3e40000000000000
+		Two129 = 1 << 129        // 2**129 0x4800000000000000
+		// R0/S0 on [0, 2]
+		R00 = -6.25000000000000000000e-02 // 0xBFB0000000000000
+		R01 = 1.40705666955189706048e-03  // 0x3F570D9F98472C61
+		R02 = -1.59955631084035597520e-05 // 0xBEF0C5C6BA169668
+		R03 = 4.96727999609584448412e-08  // 0x3E6AAAFA46CA0BD9
+		S01 = 1.91537599538363460805e-02  // 0x3F939D0B12637E53
+		S02 = 1.85946785588630915560e-04  // 0x3F285F56B9CDF664
+		S03 = 1.17718464042623683263e-06  // 0x3EB3BFF8333F8498
+		S04 = 5.04636257076217042715e-09  // 0x3E35AC88C97DFF2C
+		S05 = 1.23542274426137913908e-11  // 0x3DAB2ACFCFB97ED8
+	)
+	// special cases
+	switch {
+	case IsNaN(x):
+		return x
+	case IsInf(x, 0) || x == 0:
+		return 0
+	}
+
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+	if x >= 2 {
+		s, c := Sincos(x)
+		ss := -s - c
+		cc := s - c
+
+		// make sure x+x does not overflow
+		if x < MaxFloat64/2 {
+			z := Cos(x + x)
+			if s*c > 0 {
+				cc = z / ss
+			} else {
+				ss = z / cc
+			}
+		}
+
+		// j1(x) = 1/sqrt(pi) * (P(1,x)*cc - Q(1,x)*ss) / sqrt(x)
+		// y1(x) = 1/sqrt(pi) * (P(1,x)*ss + Q(1,x)*cc) / sqrt(x)
+
+		var z float64
+		if x > Two129 {
+			z = (1 / SqrtPi) * cc / Sqrt(x)
+		} else {
+			u := pone(x)
+			v := qone(x)
+			z = (1 / SqrtPi) * (u*cc - v*ss) / Sqrt(x)
+		}
+		if sign {
+			return -z
+		}
+		return z
+	}
+	if x < TwoM27 { // |x|<2**-27
+		return 0.5 * x // inexact if x!=0 necessary
+	}
+	z := x * x
+	r := z * (R00 + z*(R01+z*(R02+z*R03)))
+	s := 1.0 + z*(S01+z*(S02+z*(S03+z*(S04+z*S05))))
+	r *= x
+	z = 0.5*x + r/s
+	if sign {
+		return -z
+	}
+	return z
+}
+
+// Y1 returns the order-one Bessel function of the second kind.
+//
+// Special cases are:
+//	Y1(+Inf) = 0
+//	Y1(0) = -Inf
+//	Y1(x < 0) = NaN
+//	Y1(NaN) = NaN
+func Y1(x float64) float64 {
+	const (
+		TwoM54 = 1.0 / (1 << 54)             // 2**-54 0x3c90000000000000
+		Two129 = 1 << 129                    // 2**129 0x4800000000000000
+		U00    = -1.96057090646238940668e-01 // 0xBFC91866143CBC8A
+		U01    = 5.04438716639811282616e-02  // 0x3FA9D3C776292CD1
+		U02    = -1.91256895875763547298e-03 // 0xBF5F55E54844F50F
+		U03    = 2.35252600561610495928e-05  // 0x3EF8AB038FA6B88E
+		U04    = -9.19099158039878874504e-08 // 0xBE78AC00569105B8
+		V00    = 1.99167318236649903973e-02  // 0x3F94650D3F4DA9F0
+		V01    = 2.02552581025135171496e-04  // 0x3F2A8C896C257764
+		V02    = 1.35608801097516229404e-06  // 0x3EB6C05A894E8CA6
+		V03    = 6.22741452364621501295e-09  // 0x3E3ABF1D5BA69A86
+		V04    = 1.66559246207992079114e-11  // 0x3DB25039DACA772A
+	)
+	// special cases
+	switch {
+	case x < 0 || IsNaN(x):
+		return NaN()
+	case IsInf(x, 1):
+		return 0
+	case x == 0:
+		return Inf(-1)
+	}
+
+	if x >= 2 {
+		s, c := Sincos(x)
+		ss := -s - c
+		cc := s - c
+
+		// make sure x+x does not overflow
+		if x < MaxFloat64/2 {
+			z := Cos(x + x)
+			if s*c > 0 {
+				cc = z / ss
+			} else {
+				ss = z / cc
+			}
+		}
+		// y1(x) = sqrt(2/(pi*x))*(p1(x)*sin(x0)+q1(x)*cos(x0))
+		// where x0 = x-3pi/4
+		//     Better formula:
+		//         cos(x0) = cos(x)cos(3pi/4)+sin(x)sin(3pi/4)
+		//                 =  1/sqrt(2) * (sin(x) - cos(x))
+		//         sin(x0) = sin(x)cos(3pi/4)-cos(x)sin(3pi/4)
+		//                 = -1/sqrt(2) * (cos(x) + sin(x))
+		// To avoid cancellation, use
+		//     sin(x) +- cos(x) = -cos(2x)/(sin(x) -+ cos(x))
+		// to compute the worse one.
+
+		var z float64
+		if x > Two129 {
+			z = (1 / SqrtPi) * ss / Sqrt(x)
+		} else {
+			u := pone(x)
+			v := qone(x)
+			z = (1 / SqrtPi) * (u*ss + v*cc) / Sqrt(x)
+		}
+		return z
+	}
+	if x <= TwoM54 { // x < 2**-54
+		return -(2 / Pi) / x
+	}
+	z := x * x
+	u := U00 + z*(U01+z*(U02+z*(U03+z*U04)))
+	v := 1 + z*(V00+z*(V01+z*(V02+z*(V03+z*V04))))
+	return x*(u/v) + (2/Pi)*(J1(x)*Log(x)-1/x)
+}
+
+// For x >= 8, the asymptotic expansions of pone is
+//      1 + 15/128 s**2 - 4725/2**15 s**4 - ..., where s = 1/x.
+// We approximate pone by
+//      pone(x) = 1 + (R/S)
+// where R = pr0 + pr1*s**2 + pr2*s**4 + ... + pr5*s**10
+//       S = 1 + ps0*s**2 + ... + ps4*s**10
+// and
+//      | pone(x)-1-R/S | <= 2**(-60.06)
+
+// for x in [inf, 8]=1/[0,0.125]
+var p1R8 = [6]float64{
+	0.00000000000000000000e+00, // 0x0000000000000000
+	1.17187499999988647970e-01, // 0x3FBDFFFFFFFFFCCE
+	1.32394806593073575129e+01, // 0x402A7A9D357F7FCE
+	4.12051854307378562225e+02, // 0x4079C0D4652EA590
+	3.87474538913960532227e+03, // 0x40AE457DA3A532CC
+	7.91447954031891731574e+03, // 0x40BEEA7AC32782DD
+}
+var p1S8 = [5]float64{
+	1.14207370375678408436e+02, // 0x405C8D458E656CAC
+	3.65093083420853463394e+03, // 0x40AC85DC964D274F
+	3.69562060269033463555e+04, // 0x40E20B8697C5BB7F
+	9.76027935934950801311e+04, // 0x40F7D42CB28F17BB
+	3.08042720627888811578e+04, // 0x40DE1511697A0B2D
+}
+
+// for x in [8,4.5454] = 1/[0.125,0.22001]
+var p1R5 = [6]float64{
+	1.31990519556243522749e-11, // 0x3DAD0667DAE1CA7D
+	1.17187493190614097638e-01, // 0x3FBDFFFFE2C10043
+	6.80275127868432871736e+00, // 0x401B36046E6315E3
+	1.08308182990189109773e+02, // 0x405B13B9452602ED
+	5.17636139533199752805e+02, // 0x40802D16D052D649
+	5.28715201363337541807e+02, // 0x408085B8BB7E0CB7
+}
+var p1S5 = [5]float64{
+	5.92805987221131331921e+01, // 0x404DA3EAA8AF633D
+	9.91401418733614377743e+02, // 0x408EFB361B066701
+	5.35326695291487976647e+03, // 0x40B4E9445706B6FB
+	7.84469031749551231769e+03, // 0x40BEA4B0B8A5BB15
+	1.50404688810361062679e+03, // 0x40978030036F5E51
+}
+
+// for x in[4.5453,2.8571] = 1/[0.2199,0.35001]
+var p1R3 = [6]float64{
+	3.02503916137373618024e-09, // 0x3E29FC21A7AD9EDD
+	1.17186865567253592491e-01, // 0x3FBDFFF55B21D17B
+	3.93297750033315640650e+00, // 0x400F76BCE85EAD8A
+	3.51194035591636932736e+01, // 0x40418F489DA6D129
+	9.10550110750781271918e+01, // 0x4056C3854D2C1837
+	4.85590685197364919645e+01, // 0x4048478F8EA83EE5
+}
+var p1S3 = [5]float64{
+	3.47913095001251519989e+01, // 0x40416549A134069C
+	3.36762458747825746741e+02, // 0x40750C3307F1A75F
+	1.04687139975775130551e+03, // 0x40905B7C5037D523
+	8.90811346398256432622e+02, // 0x408BD67DA32E31E9
+	1.03787932439639277504e+02, // 0x4059F26D7C2EED53
+}
+
+// for x in [2.8570,2] = 1/[0.3499,0.5]
+var p1R2 = [6]float64{
+	1.07710830106873743082e-07, // 0x3E7CE9D4F65544F4
+	1.17176219462683348094e-01, // 0x3FBDFF42BE760D83
+	2.36851496667608785174e+00, // 0x4002F2B7F98FAEC0
+	1.22426109148261232917e+01, // 0x40287C377F71A964
+	1.76939711271687727390e+01, // 0x4031B1A8177F8EE2
+	5.07352312588818499250e+00, // 0x40144B49A574C1FE
+}
+var p1S2 = [5]float64{
+	2.14364859363821409488e+01, // 0x40356FBD8AD5ECDC
+	1.25290227168402751090e+02, // 0x405F529314F92CD5
+	2.32276469057162813669e+02, // 0x406D08D8D5A2DBD9
+	1.17679373287147100768e+02, // 0x405D6B7ADA1884A9
+	8.36463893371618283368e+00, // 0x4020BAB1F44E5192
+}
+
+func pone(x float64) float64 {
+	var p *[6]float64
+	var q *[5]float64
+	if x >= 8 {
+		p = &p1R8
+		q = &p1S8
+	} else if x >= 4.5454 {
+		p = &p1R5
+		q = &p1S5
+	} else if x >= 2.8571 {
+		p = &p1R3
+		q = &p1S3
+	} else if x >= 2 {
+		p = &p1R2
+		q = &p1S2
+	}
+	z := 1 / (x * x)
+	r := p[0] + z*(p[1]+z*(p[2]+z*(p[3]+z*(p[4]+z*p[5]))))
+	s := 1.0 + z*(q[0]+z*(q[1]+z*(q[2]+z*(q[3]+z*q[4]))))
+	return 1 + r/s
+}
+
+// For x >= 8, the asymptotic expansions of qone is
+//      3/8 s - 105/1024 s**3 - ..., where s = 1/x.
+// We approximate qone by
+//      qone(x) = s*(0.375 + (R/S))
+// where R = qr1*s**2 + qr2*s**4 + ... + qr5*s**10
+//       S = 1 + qs1*s**2 + ... + qs6*s**12
+// and
+//      | qone(x)/s -0.375-R/S | <= 2**(-61.13)
+
+// for x in [inf, 8] = 1/[0,0.125]
+var q1R8 = [6]float64{
+	0.00000000000000000000e+00,  // 0x0000000000000000
+	-1.02539062499992714161e-01, // 0xBFBA3FFFFFFFFDF3
+	-1.62717534544589987888e+01, // 0xC0304591A26779F7
+	-7.59601722513950107896e+02, // 0xC087BCD053E4B576
+	-1.18498066702429587167e+04, // 0xC0C724E740F87415
+	-4.84385124285750353010e+04, // 0xC0E7A6D065D09C6A
+}
+var q1S8 = [6]float64{
+	1.61395369700722909556e+02,  // 0x40642CA6DE5BCDE5
+	7.82538599923348465381e+03,  // 0x40BE9162D0D88419
+	1.33875336287249578163e+05,  // 0x4100579AB0B75E98
+	7.19657723683240939863e+05,  // 0x4125F65372869C19
+	6.66601232617776375264e+05,  // 0x412457D27719AD5C
+	-2.94490264303834643215e+05, // 0xC111F9690EA5AA18
+}
+
+// for x in [8,4.5454] = 1/[0.125,0.22001]
+var q1R5 = [6]float64{
+	-2.08979931141764104297e-11, // 0xBDB6FA431AA1A098
+	-1.02539050241375426231e-01, // 0xBFBA3FFFCB597FEF
+	-8.05644828123936029840e+00, // 0xC0201CE6CA03AD4B
+	-1.83669607474888380239e+02, // 0xC066F56D6CA7B9B0
+	-1.37319376065508163265e+03, // 0xC09574C66931734F
+	-2.61244440453215656817e+03, // 0xC0A468E388FDA79D
+}
+var q1S5 = [6]float64{
+	8.12765501384335777857e+01,  // 0x405451B2FF5A11B2
+	1.99179873460485964642e+03,  // 0x409F1F31E77BF839
+	1.74684851924908907677e+04,  // 0x40D10F1F0D64CE29
+	4.98514270910352279316e+04,  // 0x40E8576DAABAD197
+	2.79480751638918118260e+04,  // 0x40DB4B04CF7C364B
+	-4.71918354795128470869e+03, // 0xC0B26F2EFCFFA004
+}
+
+// for x in [4.5454,2.8571] = 1/[0.2199,0.35001] ???
+var q1R3 = [6]float64{
+	-5.07831226461766561369e-09, // 0xBE35CFA9D38FC84F
+	-1.02537829820837089745e-01, // 0xBFBA3FEB51AEED54
+	-4.61011581139473403113e+00, // 0xC01270C23302D9FF
+	-5.78472216562783643212e+01, // 0xC04CEC71C25D16DA
+	-2.28244540737631695038e+02, // 0xC06C87D34718D55F
+	-2.19210128478909325622e+02, // 0xC06B66B95F5C1BF6
+}
+var q1S3 = [6]float64{
+	4.76651550323729509273e+01,  // 0x4047D523CCD367E4
+	6.73865112676699709482e+02,  // 0x40850EEBC031EE3E
+	3.38015286679526343505e+03,  // 0x40AA684E448E7C9A
+	5.54772909720722782367e+03,  // 0x40B5ABBAA61D54A6
+	1.90311919338810798763e+03,  // 0x409DBC7A0DD4DF4B
+	-1.35201191444307340817e+02, // 0xC060E670290A311F
+}
+
+// for x in [2.8570,2] = 1/[0.3499,0.5]
+var q1R2 = [6]float64{
+	-1.78381727510958865572e-07, // 0xBE87F12644C626D2
+	-1.02517042607985553460e-01, // 0xBFBA3E8E9148B010
+	-2.75220568278187460720e+00, // 0xC006048469BB4EDA
+	-1.96636162643703720221e+01, // 0xC033A9E2C168907F
+	-4.23253133372830490089e+01, // 0xC04529A3DE104AAA
+	-2.13719211703704061733e+01, // 0xC0355F3639CF6E52
+}
+var q1S2 = [6]float64{
+	2.95333629060523854548e+01,  // 0x403D888A78AE64FF
+	2.52981549982190529136e+02,  // 0x406F9F68DB821CBA
+	7.57502834868645436472e+02,  // 0x4087AC05CE49A0F7
+	7.39393205320467245656e+02,  // 0x40871B2548D4C029
+	1.55949003336666123687e+02,  // 0x40637E5E3C3ED8D4
+	-4.95949898822628210127e+00, // 0xC013D686E71BE86B
+}
+
+func qone(x float64) float64 {
+	var p, q *[6]float64
+	if x >= 8 {
+		p = &q1R8
+		q = &q1S8
+	} else if x >= 4.5454 {
+		p = &q1R5
+		q = &q1S5
+	} else if x >= 2.8571 {
+		p = &q1R3
+		q = &q1S3
+	} else if x >= 2 {
+		p = &q1R2
+		q = &q1S2
+	}
+	z := 1 / (x * x)
+	r := p[0] + z*(p[1]+z*(p[2]+z*(p[3]+z*(p[4]+z*p[5]))))
+	s := 1 + z*(q[0]+z*(q[1]+z*(q[2]+z*(q[3]+z*(q[4]+z*q[5])))))
+	return (0.375 + r/s) / x
+}
diff --git a/contrib/go/_std_1.18/src/math/jn.go b/contrib/go/_std_1.18/src/math/jn.go
new file mode 100644
index 0000000000..b1aca8ff6b
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/jn.go
@@ -0,0 +1,304 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Bessel function of the first and second kinds of order n.
+*/
+
+// The original C code and the long comment below are
+// from FreeBSD's /usr/src/lib/msun/src/e_jn.c and
+// came with this notice. The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+// __ieee754_jn(n, x), __ieee754_yn(n, x)
+// floating point Bessel's function of the 1st and 2nd kind
+// of order n
+//
+// Special cases:
+//      y0(0)=y1(0)=yn(n,0) = -inf with division by zero signal;
+//      y0(-ve)=y1(-ve)=yn(n,-ve) are NaN with invalid signal.
+// Note 2. About jn(n,x), yn(n,x)
+//      For n=0, j0(x) is called,
+//      for n=1, j1(x) is called,
+//      for n<x, forward recursion is used starting
+//      from values of j0(x) and j1(x).
+//      for n>x, a continued fraction approximation to
+//      j(n,x)/j(n-1,x) is evaluated and then backward
+//      recursion is used starting from a supposed value
+//      for j(n,x). The resulting value of j(0,x) is
+//      compared with the actual value to correct the
+//      supposed value of j(n,x).
+//
+//      yn(n,x) is similar in all respects, except
+//      that forward recursion is used for all
+//      values of n>1.
+
+// Jn returns the order-n Bessel function of the first kind.
+//
+// Special cases are:
+//	Jn(n, ±Inf) = 0
+//	Jn(n, NaN) = NaN
+func Jn(n int, x float64) float64 {
+	const (
+		TwoM29 = 1.0 / (1 << 29) // 2**-29 0x3e10000000000000
+		Two302 = 1 << 302        // 2**302 0x52D0000000000000
+	)
+	// special cases
+	switch {
+	case IsNaN(x):
+		return x
+	case IsInf(x, 0):
+		return 0
+	}
+	// J(-n, x) = (-1)**n * J(n, x), J(n, -x) = (-1)**n * J(n, x)
+	// Thus, J(-n, x) = J(n, -x)
+
+	if n == 0 {
+		return J0(x)
+	}
+	if x == 0 {
+		return 0
+	}
+	if n < 0 {
+		n, x = -n, -x
+	}
+	if n == 1 {
+		return J1(x)
+	}
+	sign := false
+	if x < 0 {
+		x = -x
+		if n&1 == 1 {
+			sign = true // odd n and negative x
+		}
+	}
+	var b float64
+	if float64(n) <= x {
+		// Safe to use J(n+1,x)=2n/x *J(n,x)-J(n-1,x)
+		if x >= Two302 { // x > 2**302
+
+			// (x >> n**2)
+			//          Jn(x) = cos(x-(2n+1)*pi/4)*sqrt(2/x*pi)
+			//          Yn(x) = sin(x-(2n+1)*pi/4)*sqrt(2/x*pi)
+			//          Let s=sin(x), c=cos(x),
+			//              xn=x-(2n+1)*pi/4, sqt2 = sqrt(2),then
+			//
+			//                 n    sin(xn)*sqt2    cos(xn)*sqt2
+			//              ----------------------------------
+			//                 0     s-c             c+s
+			//                 1    -s-c            -c+s
+			//                 2    -s+c            -c-s
+			//                 3     s+c             c-s
+
+			var temp float64
+			switch s, c := Sincos(x); n & 3 {
+			case 0:
+				temp = c + s
+			case 1:
+				temp = -c + s
+			case 2:
+				temp = -c - s
+			case 3:
+				temp = c - s
+			}
+			b = (1 / SqrtPi) * temp / Sqrt(x)
+		} else {
+			b = J1(x)
+			for i, a := 1, J0(x); i < n; i++ {
+				a, b = b, b*(float64(i+i)/x)-a // avoid underflow
+			}
+		}
+	} else {
+		if x < TwoM29 { // x < 2**-29
+			// x is tiny, return the first Taylor expansion of J(n,x)
+			// J(n,x) = 1/n!*(x/2)**n  - ...
+
+			if n > 33 { // underflow
+				b = 0
+			} else {
+				temp := x * 0.5
+				b = temp
+				a := 1.0
+				for i := 2; i <= n; i++ {
+					a *= float64(i) // a = n!
+					b *= temp       // b = (x/2)**n
+				}
+				b /= a
+			}
+		} else {
+			// use backward recurrence
+			//                      x      x**2      x**2
+			//  J(n,x)/J(n-1,x) =  ----   ------   ------   .....
+			//                      2n  - 2(n+1) - 2(n+2)
+			//
+			//                      1      1        1
+			//  (for large x)   =  ----  ------   ------   .....
+			//                      2n   2(n+1)   2(n+2)
+			//                      -- - ------ - ------ -
+			//                       x     x         x
+			//
+			// Let w = 2n/x and h=2/x, then the above quotient
+			// is equal to the continued fraction:
+			//                  1
+			//      = -----------------------
+			//                     1
+			//         w - -----------------
+			//                        1
+			//              w+h - ---------
+			//                     w+2h - ...
+			//
+			// To determine how many terms needed, let
+			// Q(0) = w, Q(1) = w(w+h) - 1,
+			// Q(k) = (w+k*h)*Q(k-1) - Q(k-2),
+			// When Q(k) > 1e4	good for single
+			// When Q(k) > 1e9	good for double
+			// When Q(k) > 1e17	good for quadruple
+
+			// determine k
+			w := float64(n+n) / x
+			h := 2 / x
+			q0 := w
+			z := w + h
+			q1 := w*z - 1
+			k := 1
+			for q1 < 1e9 {
+				k++
+				z += h
+				q0, q1 = q1, z*q1-q0
+			}
+			m := n + n
+			t := 0.0
+			for i := 2 * (n + k); i >= m; i -= 2 {
+				t = 1 / (float64(i)/x - t)
+			}
+			a := t
+			b = 1
+			//  estimate log((2/x)**n*n!) = n*log(2/x)+n*ln(n)
+			//  Hence, if n*(log(2n/x)) > ...
+			//  single 8.8722839355e+01
+			//  double 7.09782712893383973096e+02
+			//  long double 1.1356523406294143949491931077970765006170e+04
+			//  then recurrent value may overflow and the result is
+			//  likely underflow to zero
+
+			tmp := float64(n)
+			v := 2 / x
+			tmp = tmp * Log(Abs(v*tmp))
+			if tmp < 7.09782712893383973096e+02 {
+				for i := n - 1; i > 0; i-- {
+					di := float64(i + i)
+					a, b = b, b*di/x-a
+				}
+			} else {
+				for i := n - 1; i > 0; i-- {
+					di := float64(i + i)
+					a, b = b, b*di/x-a
+					// scale b to avoid spurious overflow
+					if b > 1e100 {
+						a /= b
+						t /= b
+						b = 1
+					}
+				}
+			}
+			b = t * J0(x) / b
+		}
+	}
+	if sign {
+		return -b
+	}
+	return b
+}
+
+// Yn returns the order-n Bessel function of the second kind.
+//
+// Special cases are:
+//	Yn(n, +Inf) = 0
+//	Yn(n ≥ 0, 0) = -Inf
+//	Yn(n < 0, 0) = +Inf if n is odd, -Inf if n is even
+//	Yn(n, x < 0) = NaN
+//	Yn(n, NaN) = NaN
+func Yn(n int, x float64) float64 {
+	const Two302 = 1 << 302 // 2**302 0x52D0000000000000
+	// special cases
+	switch {
+	case x < 0 || IsNaN(x):
+		return NaN()
+	case IsInf(x, 1):
+		return 0
+	}
+
+	if n == 0 {
+		return Y0(x)
+	}
+	if x == 0 {
+		if n < 0 && n&1 == 1 {
+			return Inf(1)
+		}
+		return Inf(-1)
+	}
+	sign := false
+	if n < 0 {
+		n = -n
+		if n&1 == 1 {
+			sign = true // sign true if n < 0 && |n| odd
+		}
+	}
+	if n == 1 {
+		if sign {
+			return -Y1(x)
+		}
+		return Y1(x)
+	}
+	var b float64
+	if x >= Two302 { // x > 2**302
+		// (x >> n**2)
+		//	    Jn(x) = cos(x-(2n+1)*pi/4)*sqrt(2/x*pi)
+		//	    Yn(x) = sin(x-(2n+1)*pi/4)*sqrt(2/x*pi)
+		//	    Let s=sin(x), c=cos(x),
+		//		xn=x-(2n+1)*pi/4, sqt2 = sqrt(2),then
+		//
+		//		   n	sin(xn)*sqt2	cos(xn)*sqt2
+		//		----------------------------------
+		//		   0	 s-c		 c+s
+		//		   1	-s-c 		-c+s
+		//		   2	-s+c		-c-s
+		//		   3	 s+c		 c-s
+
+		var temp float64
+		switch s, c := Sincos(x); n & 3 {
+		case 0:
+			temp = s - c
+		case 1:
+			temp = -s - c
+		case 2:
+			temp = -s + c
+		case 3:
+			temp = s + c
+		}
+		b = (1 / SqrtPi) * temp / Sqrt(x)
+	} else {
+		a := Y0(x)
+		b = Y1(x)
+		// quit if b is -inf
+		for i := 1; i < n && !IsInf(b, -1); i++ {
+			a, b = b, (float64(i+i)/x)*b-a
+		}
+	}
+	if sign {
+		return -b
+	}
+	return b
+}
diff --git a/contrib/go/_std_1.18/src/math/ldexp.go b/contrib/go/_std_1.18/src/math/ldexp.go
new file mode 100644
index 0000000000..55c82f1e84
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/ldexp.go
@@ -0,0 +1,50 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Ldexp is the inverse of Frexp.
+// It returns frac × 2**exp.
+//
+// Special cases are:
+//	Ldexp(±0, exp) = ±0
+//	Ldexp(±Inf, exp) = ±Inf
+//	Ldexp(NaN, exp) = NaN
+func Ldexp(frac float64, exp int) float64 {
+	if haveArchLdexp {
+		return archLdexp(frac, exp)
+	}
+	return ldexp(frac, exp)
+}
+
+func ldexp(frac float64, exp int) float64 {
+	// special cases
+	switch {
+	case frac == 0:
+		return frac // correctly return -0
+	case IsInf(frac, 0) || IsNaN(frac):
+		return frac
+	}
+	frac, e := normalize(frac)
+	exp += e
+	x := Float64bits(frac)
+	exp += int(x>>shift)&mask - bias
+	if exp < -1075 {
+		return Copysign(0, frac) // underflow
+	}
+	if exp > 1023 { // overflow
+		if frac < 0 {
+			return Inf(-1)
+		}
+		return Inf(1)
+	}
+	var m float64 = 1
+	if exp < -1022 { // denormal
+		exp += 53
+		m = 1.0 / (1 << 53) // 2**-53
+	}
+	x &^= mask << shift
+	x |= uint64(exp+bias) << shift
+	return m * Float64frombits(x)
+}
diff --git a/contrib/go/_std_1.18/src/math/lgamma.go b/contrib/go/_std_1.18/src/math/lgamma.go
new file mode 100644
index 0000000000..7af5871744
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/lgamma.go
@@ -0,0 +1,365 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Floating-point logarithm of the Gamma function.
+*/
+
+// The original C code and the long comment below are
+// from FreeBSD's /usr/src/lib/msun/src/e_lgamma_r.c and
+// came with this notice. The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+// __ieee754_lgamma_r(x, signgamp)
+// Reentrant version of the logarithm of the Gamma function
+// with user provided pointer for the sign of Gamma(x).
+//
+// Method:
+//   1. Argument Reduction for 0 < x <= 8
+//      Since gamma(1+s)=s*gamma(s), for x in [0,8], we may
+//      reduce x to a number in [1.5,2.5] by
+//              lgamma(1+s) = log(s) + lgamma(s)
+//      for example,
+//              lgamma(7.3) = log(6.3) + lgamma(6.3)
+//                          = log(6.3*5.3) + lgamma(5.3)
+//                          = log(6.3*5.3*4.3*3.3*2.3) + lgamma(2.3)
+//   2. Polynomial approximation of lgamma around its
+//      minimum (ymin=1.461632144968362245) to maintain monotonicity.
+//      On [ymin-0.23, ymin+0.27] (i.e., [1.23164,1.73163]), use
+//              Let z = x-ymin;
+//              lgamma(x) = -1.214862905358496078218 + z**2*poly(z)
+//              poly(z) is a 14 degree polynomial.
+//   2. Rational approximation in the primary interval [2,3]
+//      We use the following approximation:
+//              s = x-2.0;
+//              lgamma(x) = 0.5*s + s*P(s)/Q(s)
+//      with accuracy
+//              |P/Q - (lgamma(x)-0.5s)| < 2**-61.71
+//      Our algorithms are based on the following observation
+//
+//                             zeta(2)-1    2    zeta(3)-1    3
+// lgamma(2+s) = s*(1-Euler) + --------- * s  -  --------- * s  + ...
+//                                 2                 3
+//
+//      where Euler = 0.5772156649... is the Euler constant, which
+//      is very close to 0.5.
+//
+//   3. For x>=8, we have
+//      lgamma(x)~(x-0.5)log(x)-x+0.5*log(2pi)+1/(12x)-1/(360x**3)+....
+//      (better formula:
+//         lgamma(x)~(x-0.5)*(log(x)-1)-.5*(log(2pi)-1) + ...)
+//      Let z = 1/x, then we approximation
+//              f(z) = lgamma(x) - (x-0.5)(log(x)-1)
+//      by
+//                                  3       5             11
+//              w = w0 + w1*z + w2*z  + w3*z  + ... + w6*z
+//      where
+//              |w - f(z)| < 2**-58.74
+//
+//   4. For negative x, since (G is gamma function)
+//              -x*G(-x)*G(x) = pi/sin(pi*x),
+//      we have
+//              G(x) = pi/(sin(pi*x)*(-x)*G(-x))
+//      since G(-x) is positive, sign(G(x)) = sign(sin(pi*x)) for x<0
+//      Hence, for x<0, signgam = sign(sin(pi*x)) and
+//              lgamma(x) = log(|Gamma(x)|)
+//                        = log(pi/(|x*sin(pi*x)|)) - lgamma(-x);
+//      Note: one should avoid computing pi*(-x) directly in the
+//            computation of sin(pi*(-x)).
+//
+//   5. Special Cases
+//              lgamma(2+s) ~ s*(1-Euler) for tiny s
+//              lgamma(1)=lgamma(2)=0
+//              lgamma(x) ~ -log(x) for tiny x
+//              lgamma(0) = lgamma(inf) = inf
+//              lgamma(-integer) = +-inf
+//
+//
+
+var _lgamA = [...]float64{
+	7.72156649015328655494e-02, // 0x3FB3C467E37DB0C8
+	3.22467033424113591611e-01, // 0x3FD4A34CC4A60FAD
+	6.73523010531292681824e-02, // 0x3FB13E001A5562A7
+	2.05808084325167332806e-02, // 0x3F951322AC92547B
+	7.38555086081402883957e-03, // 0x3F7E404FB68FEFE8
+	2.89051383673415629091e-03, // 0x3F67ADD8CCB7926B
+	1.19270763183362067845e-03, // 0x3F538A94116F3F5D
+	5.10069792153511336608e-04, // 0x3F40B6C689B99C00
+	2.20862790713908385557e-04, // 0x3F2CF2ECED10E54D
+	1.08011567247583939954e-04, // 0x3F1C5088987DFB07
+	2.52144565451257326939e-05, // 0x3EFA7074428CFA52
+	4.48640949618915160150e-05, // 0x3F07858E90A45837
+}
+var _lgamR = [...]float64{
+	1.0,                        // placeholder
+	1.39200533467621045958e+00, // 0x3FF645A762C4AB74
+	7.21935547567138069525e-01, // 0x3FE71A1893D3DCDC
+	1.71933865632803078993e-01, // 0x3FC601EDCCFBDF27
+	1.86459191715652901344e-02, // 0x3F9317EA742ED475
+	7.77942496381893596434e-04, // 0x3F497DDACA41A95B
+	7.32668430744625636189e-06, // 0x3EDEBAF7A5B38140
+}
+var _lgamS = [...]float64{
+	-7.72156649015328655494e-02, // 0xBFB3C467E37DB0C8
+	2.14982415960608852501e-01,  // 0x3FCB848B36E20878
+	3.25778796408930981787e-01,  // 0x3FD4D98F4F139F59
+	1.46350472652464452805e-01,  // 0x3FC2BB9CBEE5F2F7
+	2.66422703033638609560e-02,  // 0x3F9B481C7E939961
+	1.84028451407337715652e-03,  // 0x3F5E26B67368F239
+	3.19475326584100867617e-05,  // 0x3F00BFECDD17E945
+}
+var _lgamT = [...]float64{
+	4.83836122723810047042e-01,  // 0x3FDEF72BC8EE38A2
+	-1.47587722994593911752e-01, // 0xBFC2E4278DC6C509
+	6.46249402391333854778e-02,  // 0x3FB08B4294D5419B
+	-3.27885410759859649565e-02, // 0xBFA0C9A8DF35B713
+	1.79706750811820387126e-02,  // 0x3F9266E7970AF9EC
+	-1.03142241298341437450e-02, // 0xBF851F9FBA91EC6A
+	6.10053870246291332635e-03,  // 0x3F78FCE0E370E344
+	-3.68452016781138256760e-03, // 0xBF6E2EFFB3E914D7
+	2.25964780900612472250e-03,  // 0x3F6282D32E15C915
+	-1.40346469989232843813e-03, // 0xBF56FE8EBF2D1AF1
+	8.81081882437654011382e-04,  // 0x3F4CDF0CEF61A8E9
+	-5.38595305356740546715e-04, // 0xBF41A6109C73E0EC
+	3.15632070903625950361e-04,  // 0x3F34AF6D6C0EBBF7
+	-3.12754168375120860518e-04, // 0xBF347F24ECC38C38
+	3.35529192635519073543e-04,  // 0x3F35FD3EE8C2D3F4
+}
+var _lgamU = [...]float64{
+	-7.72156649015328655494e-02, // 0xBFB3C467E37DB0C8
+	6.32827064025093366517e-01,  // 0x3FE4401E8B005DFF
+	1.45492250137234768737e+00,  // 0x3FF7475CD119BD6F
+	9.77717527963372745603e-01,  // 0x3FEF497644EA8450
+	2.28963728064692451092e-01,  // 0x3FCD4EAEF6010924
+	1.33810918536787660377e-02,  // 0x3F8B678BBF2BAB09
+}
+var _lgamV = [...]float64{
+	1.0,
+	2.45597793713041134822e+00, // 0x4003A5D7C2BD619C
+	2.12848976379893395361e+00, // 0x40010725A42B18F5
+	7.69285150456672783825e-01, // 0x3FE89DFBE45050AF
+	1.04222645593369134254e-01, // 0x3FBAAE55D6537C88
+	3.21709242282423911810e-03, // 0x3F6A5ABB57D0CF61
+}
+var _lgamW = [...]float64{
+	4.18938533204672725052e-01,  // 0x3FDACFE390C97D69
+	8.33333333333329678849e-02,  // 0x3FB555555555553B
+	-2.77777777728775536470e-03, // 0xBF66C16C16B02E5C
+	7.93650558643019558500e-04,  // 0x3F4A019F98CF38B6
+	-5.95187557450339963135e-04, // 0xBF4380CB8C0FE741
+	8.36339918996282139126e-04,  // 0x3F4B67BA4CDAD5D1
+	-1.63092934096575273989e-03, // 0xBF5AB89D0B9E43E4
+}
+
+// Lgamma returns the natural logarithm and sign (-1 or +1) of Gamma(x).
+//
+// Special cases are:
+//	Lgamma(+Inf) = +Inf
+//	Lgamma(0) = +Inf
+//	Lgamma(-integer) = +Inf
+//	Lgamma(-Inf) = -Inf
+//	Lgamma(NaN) = NaN
+func Lgamma(x float64) (lgamma float64, sign int) {
+	const (
+		Ymin  = 1.461632144968362245
+		Two52 = 1 << 52                     // 0x4330000000000000 ~4.5036e+15
+		Two53 = 1 << 53                     // 0x4340000000000000 ~9.0072e+15
+		Two58 = 1 << 58                     // 0x4390000000000000 ~2.8823e+17
+		Tiny  = 1.0 / (1 << 70)             // 0x3b90000000000000 ~8.47033e-22
+		Tc    = 1.46163214496836224576e+00  // 0x3FF762D86356BE3F
+		Tf    = -1.21486290535849611461e-01 // 0xBFBF19B9BCC38A42
+		// Tt = -(tail of Tf)
+		Tt = -3.63867699703950536541e-18 // 0xBC50C7CAA48A971F
+	)
+	// special cases
+	sign = 1
+	switch {
+	case IsNaN(x):
+		lgamma = x
+		return
+	case IsInf(x, 0):
+		lgamma = x
+		return
+	case x == 0:
+		lgamma = Inf(1)
+		return
+	}
+
+	neg := false
+	if x < 0 {
+		x = -x
+		neg = true
+	}
+
+	if x < Tiny { // if |x| < 2**-70, return -log(|x|)
+		if neg {
+			sign = -1
+		}
+		lgamma = -Log(x)
+		return
+	}
+	var nadj float64
+	if neg {
+		if x >= Two52 { // |x| >= 2**52, must be -integer
+			lgamma = Inf(1)
+			return
+		}
+		t := sinPi(x)
+		if t == 0 {
+			lgamma = Inf(1) // -integer
+			return
+		}
+		nadj = Log(Pi / Abs(t*x))
+		if t < 0 {
+			sign = -1
+		}
+	}
+
+	switch {
+	case x == 1 || x == 2: // purge off 1 and 2
+		lgamma = 0
+		return
+	case x < 2: // use lgamma(x) = lgamma(x+1) - log(x)
+		var y float64
+		var i int
+		if x <= 0.9 {
+			lgamma = -Log(x)
+			switch {
+			case x >= (Ymin - 1 + 0.27): // 0.7316 <= x <=  0.9
+				y = 1 - x
+				i = 0
+			case x >= (Ymin - 1 - 0.27): // 0.2316 <= x < 0.7316
+				y = x - (Tc - 1)
+				i = 1
+			default: // 0 < x < 0.2316
+				y = x
+				i = 2
+			}
+		} else {
+			lgamma = 0
+			switch {
+			case x >= (Ymin + 0.27): // 1.7316 <= x < 2
+				y = 2 - x
+				i = 0
+			case x >= (Ymin - 0.27): // 1.2316 <= x < 1.7316
+				y = x - Tc
+				i = 1
+			default: // 0.9 < x < 1.2316
+				y = x - 1
+				i = 2
+			}
+		}
+		switch i {
+		case 0:
+			z := y * y
+			p1 := _lgamA[0] + z*(_lgamA[2]+z*(_lgamA[4]+z*(_lgamA[6]+z*(_lgamA[8]+z*_lgamA[10]))))
+			p2 := z * (_lgamA[1] + z*(+_lgamA[3]+z*(_lgamA[5]+z*(_lgamA[7]+z*(_lgamA[9]+z*_lgamA[11])))))
+			p := y*p1 + p2
+			lgamma += (p - 0.5*y)
+		case 1:
+			z := y * y
+			w := z * y
+			p1 := _lgamT[0] + w*(_lgamT[3]+w*(_lgamT[6]+w*(_lgamT[9]+w*_lgamT[12]))) // parallel comp
+			p2 := _lgamT[1] + w*(_lgamT[4]+w*(_lgamT[7]+w*(_lgamT[10]+w*_lgamT[13])))
+			p3 := _lgamT[2] + w*(_lgamT[5]+w*(_lgamT[8]+w*(_lgamT[11]+w*_lgamT[14])))
+			p := z*p1 - (Tt - w*(p2+y*p3))
+			lgamma += (Tf + p)
+		case 2:
+			p1 := y * (_lgamU[0] + y*(_lgamU[1]+y*(_lgamU[2]+y*(_lgamU[3]+y*(_lgamU[4]+y*_lgamU[5])))))
+			p2 := 1 + y*(_lgamV[1]+y*(_lgamV[2]+y*(_lgamV[3]+y*(_lgamV[4]+y*_lgamV[5]))))
+			lgamma += (-0.5*y + p1/p2)
+		}
+	case x < 8: // 2 <= x < 8
+		i := int(x)
+		y := x - float64(i)
+		p := y * (_lgamS[0] + y*(_lgamS[1]+y*(_lgamS[2]+y*(_lgamS[3]+y*(_lgamS[4]+y*(_lgamS[5]+y*_lgamS[6]))))))
+		q := 1 + y*(_lgamR[1]+y*(_lgamR[2]+y*(_lgamR[3]+y*(_lgamR[4]+y*(_lgamR[5]+y*_lgamR[6])))))
+		lgamma = 0.5*y + p/q
+		z := 1.0 // Lgamma(1+s) = Log(s) + Lgamma(s)
+		switch i {
+		case 7:
+			z *= (y + 6)
+			fallthrough
+		case 6:
+			z *= (y + 5)
+			fallthrough
+		case 5:
+			z *= (y + 4)
+			fallthrough
+		case 4:
+			z *= (y + 3)
+			fallthrough
+		case 3:
+			z *= (y + 2)
+			lgamma += Log(z)
+		}
+	case x < Two58: // 8 <= x < 2**58
+		t := Log(x)
+		z := 1 / x
+		y := z * z
+		w := _lgamW[0] + z*(_lgamW[1]+y*(_lgamW[2]+y*(_lgamW[3]+y*(_lgamW[4]+y*(_lgamW[5]+y*_lgamW[6])))))
+		lgamma = (x-0.5)*(t-1) + w
+	default: // 2**58 <= x <= Inf
+		lgamma = x * (Log(x) - 1)
+	}
+	if neg {
+		lgamma = nadj - lgamma
+	}
+	return
+}
+
+// sinPi(x) is a helper function for negative x
+func sinPi(x float64) float64 {
+	const (
+		Two52 = 1 << 52 // 0x4330000000000000 ~4.5036e+15
+		Two53 = 1 << 53 // 0x4340000000000000 ~9.0072e+15
+	)
+	if x < 0.25 {
+		return -Sin(Pi * x)
+	}
+
+	// argument reduction
+	z := Floor(x)
+	var n int
+	if z != x { // inexact
+		x = Mod(x, 2)
+		n = int(x * 4)
+	} else {
+		if x >= Two53 { // x must be even
+			x = 0
+			n = 0
+		} else {
+			if x < Two52 {
+				z = x + Two52 // exact
+			}
+			n = int(1 & Float64bits(z))
+			x = float64(n)
+			n <<= 2
+		}
+	}
+	switch n {
+	case 0:
+		x = Sin(Pi * x)
+	case 1, 2:
+		x = Cos(Pi * (0.5 - x))
+	case 3, 4:
+		x = Sin(Pi * (1 - x))
+	case 5, 6:
+		x = -Cos(Pi * (x - 1.5))
+	default:
+		x = Sin(Pi * (x - 2))
+	}
+	return -x
+}
diff --git a/contrib/go/_std_1.18/src/math/log.go b/contrib/go/_std_1.18/src/math/log.go
new file mode 100644
index 0000000000..1b3e306adf
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/log.go
@@ -0,0 +1,128 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Floating-point logarithm.
+*/
+
+// The original C code, the long comment, and the constants
+// below are from FreeBSD's /usr/src/lib/msun/src/e_log.c
+// and came with this notice. The go code is a simpler
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+// __ieee754_log(x)
+// Return the logarithm of x
+//
+// Method :
+//   1. Argument Reduction: find k and f such that
+//			x = 2**k * (1+f),
+//	   where  sqrt(2)/2 < 1+f < sqrt(2) .
+//
+//   2. Approximation of log(1+f).
+//	Let s = f/(2+f) ; based on log(1+f) = log(1+s) - log(1-s)
+//		 = 2s + 2/3 s**3 + 2/5 s**5 + .....,
+//	     	 = 2s + s*R
+//      We use a special Reme algorithm on [0,0.1716] to generate
+//	a polynomial of degree 14 to approximate R.  The maximum error
+//	of this polynomial approximation is bounded by 2**-58.45. In
+//	other words,
+//		        2      4      6      8      10      12      14
+//	    R(z) ~ L1*s +L2*s +L3*s +L4*s +L5*s  +L6*s  +L7*s
+//	(the values of L1 to L7 are listed in the program) and
+//	    |      2          14          |     -58.45
+//	    | L1*s +...+L7*s    -  R(z) | <= 2
+//	    |                             |
+//	Note that 2s = f - s*f = f - hfsq + s*hfsq, where hfsq = f*f/2.
+//	In order to guarantee error in log below 1ulp, we compute log by
+//		log(1+f) = f - s*(f - R)		(if f is not too large)
+//		log(1+f) = f - (hfsq - s*(hfsq+R)).	(better accuracy)
+//
+//	3. Finally,  log(x) = k*Ln2 + log(1+f).
+//			    = k*Ln2_hi+(f-(hfsq-(s*(hfsq+R)+k*Ln2_lo)))
+//	   Here Ln2 is split into two floating point number:
+//			Ln2_hi + Ln2_lo,
+//	   where n*Ln2_hi is always exact for |n| < 2000.
+//
+// Special cases:
+//	log(x) is NaN with signal if x < 0 (including -INF) ;
+//	log(+INF) is +INF; log(0) is -INF with signal;
+//	log(NaN) is that NaN with no signal.
+//
+// Accuracy:
+//	according to an error analysis, the error is always less than
+//	1 ulp (unit in the last place).
+//
+// Constants:
+// The hexadecimal values are the intended ones for the following
+// constants. The decimal values may be used, provided that the
+// compiler will convert from decimal to binary accurately enough
+// to produce the hexadecimal values shown.
+
+// Log returns the natural logarithm of x.
+//
+// Special cases are:
+//	Log(+Inf) = +Inf
+//	Log(0) = -Inf
+//	Log(x < 0) = NaN
+//	Log(NaN) = NaN
+func Log(x float64) float64 {
+	if haveArchLog {
+		return archLog(x)
+	}
+	return log(x)
+}
+
+func log(x float64) float64 {
+	const (
+		Ln2Hi = 6.93147180369123816490e-01 /* 3fe62e42 fee00000 */
+		Ln2Lo = 1.90821492927058770002e-10 /* 3dea39ef 35793c76 */
+		L1    = 6.666666666666735130e-01   /* 3FE55555 55555593 */
+		L2    = 3.999999999940941908e-01   /* 3FD99999 9997FA04 */
+		L3    = 2.857142874366239149e-01   /* 3FD24924 94229359 */
+		L4    = 2.222219843214978396e-01   /* 3FCC71C5 1D8E78AF */
+		L5    = 1.818357216161805012e-01   /* 3FC74664 96CB03DE */
+		L6    = 1.531383769920937332e-01   /* 3FC39A09 D078C69F */
+		L7    = 1.479819860511658591e-01   /* 3FC2F112 DF3E5244 */
+	)
+
+	// special cases
+	switch {
+	case IsNaN(x) || IsInf(x, 1):
+		return x
+	case x < 0:
+		return NaN()
+	case x == 0:
+		return Inf(-1)
+	}
+
+	// reduce
+	f1, ki := Frexp(x)
+	if f1 < Sqrt2/2 {
+		f1 *= 2
+		ki--
+	}
+	f := f1 - 1
+	k := float64(ki)
+
+	// compute
+	s := f / (2 + f)
+	s2 := s * s
+	s4 := s2 * s2
+	t1 := s2 * (L1 + s4*(L3+s4*(L5+s4*L7)))
+	t2 := s4 * (L2 + s4*(L4+s4*L6))
+	R := t1 + t2
+	hfsq := 0.5 * f * f
+	return k*Ln2Hi - ((hfsq - (s*(hfsq+R) + k*Ln2Lo)) - f)
+}
diff --git a/contrib/go/_std_1.18/src/math/log10.go b/contrib/go/_std_1.18/src/math/log10.go
new file mode 100644
index 0000000000..e6916a53b6
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/log10.go
@@ -0,0 +1,37 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Log10 returns the decimal logarithm of x.
+// The special cases are the same as for Log.
+func Log10(x float64) float64 {
+	if haveArchLog10 {
+		return archLog10(x)
+	}
+	return log10(x)
+}
+
+func log10(x float64) float64 {
+	return Log(x) * (1 / Ln10)
+}
+
+// Log2 returns the binary logarithm of x.
+// The special cases are the same as for Log.
+func Log2(x float64) float64 {
+	if haveArchLog2 {
+		return archLog2(x)
+	}
+	return log2(x)
+}
+
+func log2(x float64) float64 {
+	frac, exp := Frexp(x)
+	// Make sure exact powers of two give an exact answer.
+	// Don't depend on Log(0.5)*(1/Ln2)+exp being exactly exp-1.
+	if frac == 0.5 {
+		return float64(exp - 1)
+	}
+	return Log(frac)*(1/Ln2) + float64(exp)
+}
diff --git a/contrib/go/_std_1.18/src/math/log1p.go b/contrib/go/_std_1.18/src/math/log1p.go
new file mode 100644
index 0000000000..c117f7245d
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/log1p.go
@@ -0,0 +1,202 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// The original C code, the long comment, and the constants
+// below are from FreeBSD's /usr/src/lib/msun/src/s_log1p.c
+// and came with this notice. The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+//
+// double log1p(double x)
+//
+// Method :
+//   1. Argument Reduction: find k and f such that
+//                      1+x = 2**k * (1+f),
+//         where  sqrt(2)/2 < 1+f < sqrt(2) .
+//
+//      Note. If k=0, then f=x is exact. However, if k!=0, then f
+//      may not be representable exactly. In that case, a correction
+//      term is need. Let u=1+x rounded. Let c = (1+x)-u, then
+//      log(1+x) - log(u) ~ c/u. Thus, we proceed to compute log(u),
+//      and add back the correction term c/u.
+//      (Note: when x > 2**53, one can simply return log(x))
+//
+//   2. Approximation of log1p(f).
+//      Let s = f/(2+f) ; based on log(1+f) = log(1+s) - log(1-s)
+//               = 2s + 2/3 s**3 + 2/5 s**5 + .....,
+//               = 2s + s*R
+//      We use a special Reme algorithm on [0,0.1716] to generate
+//      a polynomial of degree 14 to approximate R The maximum error
+//      of this polynomial approximation is bounded by 2**-58.45. In
+//      other words,
+//                      2      4      6      8      10      12      14
+//          R(z) ~ Lp1*s +Lp2*s +Lp3*s +Lp4*s +Lp5*s  +Lp6*s  +Lp7*s
+//      (the values of Lp1 to Lp7 are listed in the program)
+//      and
+//          |      2          14          |     -58.45
+//          | Lp1*s +...+Lp7*s    -  R(z) | <= 2
+//          |                             |
+//      Note that 2s = f - s*f = f - hfsq + s*hfsq, where hfsq = f*f/2.
+//      In order to guarantee error in log below 1ulp, we compute log
+//      by
+//              log1p(f) = f - (hfsq - s*(hfsq+R)).
+//
+//   3. Finally, log1p(x) = k*ln2 + log1p(f).
+//                        = k*ln2_hi+(f-(hfsq-(s*(hfsq+R)+k*ln2_lo)))
+//      Here ln2 is split into two floating point number:
+//                   ln2_hi + ln2_lo,
+//      where n*ln2_hi is always exact for |n| < 2000.
+//
+// Special cases:
+//      log1p(x) is NaN with signal if x < -1 (including -INF) ;
+//      log1p(+INF) is +INF; log1p(-1) is -INF with signal;
+//      log1p(NaN) is that NaN with no signal.
+//
+// Accuracy:
+//      according to an error analysis, the error is always less than
+//      1 ulp (unit in the last place).
+//
+// Constants:
+// The hexadecimal values are the intended ones for the following
+// constants. The decimal values may be used, provided that the
+// compiler will convert from decimal to binary accurately enough
+// to produce the hexadecimal values shown.
+//
+// Note: Assuming log() return accurate answer, the following
+//       algorithm can be used to compute log1p(x) to within a few ULP:
+//
+//              u = 1+x;
+//              if(u==1.0) return x ; else
+//                         return log(u)*(x/(u-1.0));
+//
+//       See HP-15C Advanced Functions Handbook, p.193.
+
+// Log1p returns the natural logarithm of 1 plus its argument x.
+// It is more accurate than Log(1 + x) when x is near zero.
+//
+// Special cases are:
+//	Log1p(+Inf) = +Inf
+//	Log1p(±0) = ±0
+//	Log1p(-1) = -Inf
+//	Log1p(x < -1) = NaN
+//	Log1p(NaN) = NaN
+func Log1p(x float64) float64 {
+	if haveArchLog1p {
+		return archLog1p(x)
+	}
+	return log1p(x)
+}
+
+func log1p(x float64) float64 {
+	const (
+		Sqrt2M1     = 4.142135623730950488017e-01  // Sqrt(2)-1 = 0x3fda827999fcef34
+		Sqrt2HalfM1 = -2.928932188134524755992e-01 // Sqrt(2)/2-1 = 0xbfd2bec333018866
+		Small       = 1.0 / (1 << 29)              // 2**-29 = 0x3e20000000000000
+		Tiny        = 1.0 / (1 << 54)              // 2**-54
+		Two53       = 1 << 53                      // 2**53
+		Ln2Hi       = 6.93147180369123816490e-01   // 3fe62e42fee00000
+		Ln2Lo       = 1.90821492927058770002e-10   // 3dea39ef35793c76
+		Lp1         = 6.666666666666735130e-01     // 3FE5555555555593
+		Lp2         = 3.999999999940941908e-01     // 3FD999999997FA04
+		Lp3         = 2.857142874366239149e-01     // 3FD2492494229359
+		Lp4         = 2.222219843214978396e-01     // 3FCC71C51D8E78AF
+		Lp5         = 1.818357216161805012e-01     // 3FC7466496CB03DE
+		Lp6         = 1.531383769920937332e-01     // 3FC39A09D078C69F
+		Lp7         = 1.479819860511658591e-01     // 3FC2F112DF3E5244
+	)
+
+	// special cases
+	switch {
+	case x < -1 || IsNaN(x): // includes -Inf
+		return NaN()
+	case x == -1:
+		return Inf(-1)
+	case IsInf(x, 1):
+		return Inf(1)
+	}
+
+	absx := Abs(x)
+
+	var f float64
+	var iu uint64
+	k := 1
+	if absx < Sqrt2M1 { //  |x| < Sqrt(2)-1
+		if absx < Small { // |x| < 2**-29
+			if absx < Tiny { // |x| < 2**-54
+				return x
+			}
+			return x - x*x*0.5
+		}
+		if x > Sqrt2HalfM1 { // Sqrt(2)/2-1 < x
+			// (Sqrt(2)/2-1) < x < (Sqrt(2)-1)
+			k = 0
+			f = x
+			iu = 1
+		}
+	}
+	var c float64
+	if k != 0 {
+		var u float64
+		if absx < Two53 { // 1<<53
+			u = 1.0 + x
+			iu = Float64bits(u)
+			k = int((iu >> 52) - 1023)
+			// correction term
+			if k > 0 {
+				c = 1.0 - (u - x)
+			} else {
+				c = x - (u - 1.0)
+			}
+			c /= u
+		} else {
+			u = x
+			iu = Float64bits(u)
+			k = int((iu >> 52) - 1023)
+			c = 0
+		}
+		iu &= 0x000fffffffffffff
+		if iu < 0x0006a09e667f3bcd { // mantissa of Sqrt(2)
+			u = Float64frombits(iu | 0x3ff0000000000000) // normalize u
+		} else {
+			k++
+			u = Float64frombits(iu | 0x3fe0000000000000) // normalize u/2
+			iu = (0x0010000000000000 - iu) >> 2
+		}
+		f = u - 1.0 // Sqrt(2)/2 < u < Sqrt(2)
+	}
+	hfsq := 0.5 * f * f
+	var s, R, z float64
+	if iu == 0 { // |f| < 2**-20
+		if f == 0 {
+			if k == 0 {
+				return 0
+			}
+			c += float64(k) * Ln2Lo
+			return float64(k)*Ln2Hi + c
+		}
+		R = hfsq * (1.0 - 0.66666666666666666*f) // avoid division
+		if k == 0 {
+			return f - R
+		}
+		return float64(k)*Ln2Hi - ((R - (float64(k)*Ln2Lo + c)) - f)
+	}
+	s = f / (2.0 + f)
+	z = s * s
+	R = z * (Lp1 + z*(Lp2+z*(Lp3+z*(Lp4+z*(Lp5+z*(Lp6+z*Lp7))))))
+	if k == 0 {
+		return f - (hfsq - s*(hfsq+R))
+	}
+	return float64(k)*Ln2Hi - ((hfsq - (s*(hfsq+R) + (float64(k)*Ln2Lo + c))) - f)
+}
diff --git a/contrib/go/_std_1.18/src/math/log_amd64.s b/contrib/go/_std_1.18/src/math/log_amd64.s
new file mode 100644
index 0000000000..d84091f23a
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/log_amd64.s
@@ -0,0 +1,112 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "textflag.h"
+
+#define HSqrt2 7.07106781186547524401e-01 // sqrt(2)/2
+#define Ln2Hi  6.93147180369123816490e-01 // 0x3fe62e42fee00000
+#define Ln2Lo  1.90821492927058770002e-10 // 0x3dea39ef35793c76
+#define L1     6.666666666666735130e-01   // 0x3FE5555555555593
+#define L2     3.999999999940941908e-01   // 0x3FD999999997FA04
+#define L3     2.857142874366239149e-01   // 0x3FD2492494229359
+#define L4     2.222219843214978396e-01   // 0x3FCC71C51D8E78AF
+#define L5     1.818357216161805012e-01   // 0x3FC7466496CB03DE
+#define L6     1.531383769920937332e-01   // 0x3FC39A09D078C69F
+#define L7     1.479819860511658591e-01   // 0x3FC2F112DF3E5244
+#define NaN    0x7FF8000000000001
+#define NegInf 0xFFF0000000000000
+#define PosInf 0x7FF0000000000000
+
+// func Log(x float64) float64
+TEXT ·archLog(SB),NOSPLIT,$0
+	// test bits for special cases
+	MOVQ    x+0(FP), BX
+	MOVQ    $~(1<<63), AX // sign bit mask
+	ANDQ    BX, AX
+	JEQ     isZero
+	MOVQ    $0, AX
+	CMPQ    AX, BX
+	JGT     isNegative
+	MOVQ    $PosInf, AX
+	CMPQ    AX, BX
+	JLE     isInfOrNaN
+	// f1, ki := math.Frexp(x); k := float64(ki)
+	MOVQ    BX, X0
+	MOVQ    $0x000FFFFFFFFFFFFF, AX
+	MOVQ    AX, X2
+	ANDPD   X0, X2
+	MOVSD   $0.5, X0 // 0x3FE0000000000000
+	ORPD    X0, X2 // X2= f1
+	SHRQ    $52, BX
+	ANDL    $0x7FF, BX
+	SUBL    $0x3FE, BX
+	XORPS   X1, X1 // break dependency for CVTSL2SD
+	CVTSL2SD BX, X1 // x1= k, x2= f1
+	// if f1 < math.Sqrt2/2 { k -= 1; f1 *= 2 }
+	MOVSD   $HSqrt2, X0 // x0= 0.7071, x1= k, x2= f1
+	CMPSD   X2, X0, 5 // cmpnlt; x0= 0 or ^0, x1= k, x2 = f1
+	MOVSD   $1.0, X3 // x0= 0 or ^0, x1= k, x2 = f1, x3= 1
+	ANDPD   X0, X3 // x0= 0 or ^0, x1= k, x2 = f1, x3= 0 or 1
+	SUBSD   X3, X1 // x0= 0 or ^0, x1= k, x2 = f1, x3= 0 or 1
+	MOVSD   $1.0, X0 // x0= 1, x1= k, x2= f1, x3= 0 or 1
+	ADDSD   X0, X3 // x0= 1, x1= k, x2= f1, x3= 1 or 2
+	MULSD   X3, X2 // x0= 1, x1= k, x2= f1
+	// f := f1 - 1
+	SUBSD   X0, X2 // x1= k, x2= f
+	// s := f / (2 + f)
+	MOVSD   $2.0, X0
+	ADDSD   X2, X0
+	MOVAPD  X2, X3
+	DIVSD   X0, X3 // x1=k, x2= f, x3= s
+	// s2 := s * s
+	MOVAPD  X3, X4 // x1= k, x2= f, x3= s
+	MULSD   X4, X4 // x1= k, x2= f, x3= s, x4= s2
+	// s4 := s2 * s2
+	MOVAPD  X4, X5 // x1= k, x2= f, x3= s, x4= s2
+	MULSD   X5, X5 // x1= k, x2= f, x3= s, x4= s2, x5= s4
+	// t1 := s2 * (L1 + s4*(L3+s4*(L5+s4*L7)))
+	MOVSD   $L7, X6
+	MULSD   X5, X6
+	ADDSD   $L5, X6
+	MULSD   X5, X6
+	ADDSD   $L3, X6
+	MULSD   X5, X6
+	ADDSD   $L1, X6
+	MULSD   X6, X4 // x1= k, x2= f, x3= s, x4= t1, x5= s4
+	// t2 := s4 * (L2 + s4*(L4+s4*L6))
+	MOVSD   $L6, X6
+	MULSD   X5, X6
+	ADDSD   $L4, X6
+	MULSD   X5, X6
+	ADDSD   $L2, X6
+	MULSD   X6, X5 // x1= k, x2= f, x3= s, x4= t1, x5= t2
+	// R := t1 + t2
+	ADDSD   X5, X4 // x1= k, x2= f, x3= s, x4= R
+	// hfsq := 0.5 * f * f
+	MOVSD   $0.5, X0
+	MULSD   X2, X0
+	MULSD   X2, X0 // x0= hfsq, x1= k, x2= f, x3= s, x4= R
+	// return k*Ln2Hi - ((hfsq - (s*(hfsq+R) + k*Ln2Lo)) - f)
+	ADDSD   X0, X4 // x0= hfsq, x1= k, x2= f, x3= s, x4= hfsq+R
+	MULSD   X4, X3 // x0= hfsq, x1= k, x2= f, x3= s*(hfsq+R)
+	MOVSD   $Ln2Lo, X4
+	MULSD   X1, X4 // x4= k*Ln2Lo
+	ADDSD   X4, X3 // x0= hfsq, x1= k, x2= f, x3= s*(hfsq+R)+k*Ln2Lo
+	SUBSD   X3, X0 // x0= hfsq-(s*(hfsq+R)+k*Ln2Lo), x1= k, x2= f
+	SUBSD   X2, X0 // x0= (hfsq-(s*(hfsq+R)+k*Ln2Lo))-f, x1= k
+	MULSD   $Ln2Hi, X1 // x0= (hfsq-(s*(hfsq+R)+k*Ln2Lo))-f, x1= k*Ln2Hi
+	SUBSD   X0, X1 // x1= k*Ln2Hi-((hfsq-(s*(hfsq+R)+k*Ln2Lo))-f)
+  	MOVSD   X1, ret+8(FP)
+	RET
+isInfOrNaN:
+	MOVQ    BX, ret+8(FP) // +Inf or NaN, return x
+	RET
+isNegative:
+	MOVQ    $NaN, AX
+	MOVQ    AX, ret+8(FP) // return NaN
+	RET
+isZero:
+	MOVQ    $NegInf, AX
+	MOVQ    AX, ret+8(FP) // return -Inf
+	RET
diff --git a/contrib/go/_std_1.18/src/math/log_asm.go b/contrib/go/_std_1.18/src/math/log_asm.go
new file mode 100644
index 0000000000..848cce13b2
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/log_asm.go
@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build amd64 || s390x
+
+package math
+
+const haveArchLog = true
+
+func archLog(x float64) float64
diff --git a/contrib/go/_std_1.18/src/math/logb.go b/contrib/go/_std_1.18/src/math/logb.go
new file mode 100644
index 0000000000..f2769d4fd7
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/logb.go
@@ -0,0 +1,50 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Logb returns the binary exponent of x.
+//
+// Special cases are:
+//	Logb(±Inf) = +Inf
+//	Logb(0) = -Inf
+//	Logb(NaN) = NaN
+func Logb(x float64) float64 {
+	// special cases
+	switch {
+	case x == 0:
+		return Inf(-1)
+	case IsInf(x, 0):
+		return Inf(1)
+	case IsNaN(x):
+		return x
+	}
+	return float64(ilogb(x))
+}
+
+// Ilogb returns the binary exponent of x as an integer.
+//
+// Special cases are:
+//	Ilogb(±Inf) = MaxInt32
+//	Ilogb(0) = MinInt32
+//	Ilogb(NaN) = MaxInt32
+func Ilogb(x float64) int {
+	// special cases
+	switch {
+	case x == 0:
+		return MinInt32
+	case IsNaN(x):
+		return MaxInt32
+	case IsInf(x, 0):
+		return MaxInt32
+	}
+	return ilogb(x)
+}
+
+// logb returns the binary exponent of x. It assumes x is finite and
+// non-zero.
+func ilogb(x float64) int {
+	x, exp := normalize(x)
+	return int((Float64bits(x)>>shift)&mask) - bias + exp
+}
diff --git a/contrib/go/_std_1.18/src/math/mod.go b/contrib/go/_std_1.18/src/math/mod.go
new file mode 100644
index 0000000000..6bc5f28832
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/mod.go
@@ -0,0 +1,51 @@
+// Copyright 2009-2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Floating-point mod function.
+*/
+
+// Mod returns the floating-point remainder of x/y.
+// The magnitude of the result is less than y and its
+// sign agrees with that of x.
+//
+// Special cases are:
+//	Mod(±Inf, y) = NaN
+//	Mod(NaN, y) = NaN
+//	Mod(x, 0) = NaN
+//	Mod(x, ±Inf) = x
+//	Mod(x, NaN) = NaN
+func Mod(x, y float64) float64 {
+	if haveArchMod {
+		return archMod(x, y)
+	}
+	return mod(x, y)
+}
+
+func mod(x, y float64) float64 {
+	if y == 0 || IsInf(x, 0) || IsNaN(x) || IsNaN(y) {
+		return NaN()
+	}
+	y = Abs(y)
+
+	yfr, yexp := Frexp(y)
+	r := x
+	if x < 0 {
+		r = -x
+	}
+
+	for r >= y {
+		rfr, rexp := Frexp(r)
+		if rfr < yfr {
+			rexp = rexp - 1
+		}
+		r = r - Ldexp(y, rexp-yexp)
+	}
+	if x < 0 {
+		r = -r
+	}
+	return r
+}
diff --git a/contrib/go/_std_1.18/src/math/modf.go b/contrib/go/_std_1.18/src/math/modf.go
new file mode 100644
index 0000000000..bf08dc6556
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/modf.go
@@ -0,0 +1,42 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Modf returns integer and fractional floating-point numbers
+// that sum to f. Both values have the same sign as f.
+//
+// Special cases are:
+//	Modf(±Inf) = ±Inf, NaN
+//	Modf(NaN) = NaN, NaN
+func Modf(f float64) (int float64, frac float64) {
+	if haveArchModf {
+		return archModf(f)
+	}
+	return modf(f)
+}
+
+func modf(f float64) (int float64, frac float64) {
+	if f < 1 {
+		switch {
+		case f < 0:
+			int, frac = Modf(-f)
+			return -int, -frac
+		case f == 0:
+			return f, f // Return -0, -0 when f == -0
+		}
+		return 0, f
+	}
+
+	x := Float64bits(f)
+	e := uint(x>>shift)&mask - bias
+
+	// Keep the top 12+e bits, the integer part; clear the rest.
+	if e < 64-12 {
+		x &^= 1<<(64-12-e) - 1
+	}
+	int = Float64frombits(x)
+	frac = f - int
+	return
+}
diff --git a/contrib/go/_std_1.18/src/math/modf_noasm.go b/contrib/go/_std_1.18/src/math/modf_noasm.go
new file mode 100644
index 0000000000..55c6a7f6e2
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/modf_noasm.go
@@ -0,0 +1,13 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !arm64 && !ppc64 && !ppc64le
+
+package math
+
+const haveArchModf = false
+
+func archModf(f float64) (int float64, frac float64) {
+	panic("not implemented")
+}
diff --git a/contrib/go/_std_1.18/src/math/nextafter.go b/contrib/go/_std_1.18/src/math/nextafter.go
new file mode 100644
index 0000000000..9088e4d248
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/nextafter.go
@@ -0,0 +1,49 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Nextafter32 returns the next representable float32 value after x towards y.
+//
+// Special cases are:
+//	Nextafter32(x, x)   = x
+//	Nextafter32(NaN, y) = NaN
+//	Nextafter32(x, NaN) = NaN
+func Nextafter32(x, y float32) (r float32) {
+	switch {
+	case IsNaN(float64(x)) || IsNaN(float64(y)): // special case
+		r = float32(NaN())
+	case x == y:
+		r = x
+	case x == 0:
+		r = float32(Copysign(float64(Float32frombits(1)), float64(y)))
+	case (y > x) == (x > 0):
+		r = Float32frombits(Float32bits(x) + 1)
+	default:
+		r = Float32frombits(Float32bits(x) - 1)
+	}
+	return
+}
+
+// Nextafter returns the next representable float64 value after x towards y.
+//
+// Special cases are:
+//	Nextafter(x, x)   = x
+//	Nextafter(NaN, y) = NaN
+//	Nextafter(x, NaN) = NaN
+func Nextafter(x, y float64) (r float64) {
+	switch {
+	case IsNaN(x) || IsNaN(y): // special case
+		r = NaN()
+	case x == y:
+		r = x
+	case x == 0:
+		r = Copysign(Float64frombits(1), y)
+	case (y > x) == (x > 0):
+		r = Float64frombits(Float64bits(x) + 1)
+	default:
+		r = Float64frombits(Float64bits(x) - 1)
+	}
+	return
+}
diff --git a/contrib/go/_std_1.18/src/math/pow.go b/contrib/go/_std_1.18/src/math/pow.go
new file mode 100644
index 0000000000..e45a044ae1
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/pow.go
@@ -0,0 +1,156 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+func isOddInt(x float64) bool {
+	xi, xf := Modf(x)
+	return xf == 0 && int64(xi)&1 == 1
+}
+
+// Special cases taken from FreeBSD's /usr/src/lib/msun/src/e_pow.c
+// updated by IEEE Std. 754-2008 "Section 9.2.1 Special values".
+
+// Pow returns x**y, the base-x exponential of y.
+//
+// Special cases are (in order):
+//	Pow(x, ±0) = 1 for any x
+//	Pow(1, y) = 1 for any y
+//	Pow(x, 1) = x for any x
+//	Pow(NaN, y) = NaN
+//	Pow(x, NaN) = NaN
+//	Pow(±0, y) = ±Inf for y an odd integer < 0
+//	Pow(±0, -Inf) = +Inf
+//	Pow(±0, +Inf) = +0
+//	Pow(±0, y) = +Inf for finite y < 0 and not an odd integer
+//	Pow(±0, y) = ±0 for y an odd integer > 0
+//	Pow(±0, y) = +0 for finite y > 0 and not an odd integer
+//	Pow(-1, ±Inf) = 1
+//	Pow(x, +Inf) = +Inf for |x| > 1
+//	Pow(x, -Inf) = +0 for |x| > 1
+//	Pow(x, +Inf) = +0 for |x| < 1
+//	Pow(x, -Inf) = +Inf for |x| < 1
+//	Pow(+Inf, y) = +Inf for y > 0
+//	Pow(+Inf, y) = +0 for y < 0
+//	Pow(-Inf, y) = Pow(-0, -y)
+//	Pow(x, y) = NaN for finite x < 0 and finite non-integer y
+func Pow(x, y float64) float64 {
+	if haveArchPow {
+		return archPow(x, y)
+	}
+	return pow(x, y)
+}
+
+func pow(x, y float64) float64 {
+	switch {
+	case y == 0 || x == 1:
+		return 1
+	case y == 1:
+		return x
+	case IsNaN(x) || IsNaN(y):
+		return NaN()
+	case x == 0:
+		switch {
+		case y < 0:
+			if isOddInt(y) {
+				return Copysign(Inf(1), x)
+			}
+			return Inf(1)
+		case y > 0:
+			if isOddInt(y) {
+				return x
+			}
+			return 0
+		}
+	case IsInf(y, 0):
+		switch {
+		case x == -1:
+			return 1
+		case (Abs(x) < 1) == IsInf(y, 1):
+			return 0
+		default:
+			return Inf(1)
+		}
+	case IsInf(x, 0):
+		if IsInf(x, -1) {
+			return Pow(1/x, -y) // Pow(-0, -y)
+		}
+		switch {
+		case y < 0:
+			return 0
+		case y > 0:
+			return Inf(1)
+		}
+	case y == 0.5:
+		return Sqrt(x)
+	case y == -0.5:
+		return 1 / Sqrt(x)
+	}
+
+	yi, yf := Modf(Abs(y))
+	if yf != 0 && x < 0 {
+		return NaN()
+	}
+	if yi >= 1<<63 {
+		// yi is a large even int that will lead to overflow (or underflow to 0)
+		// for all x except -1 (x == 1 was handled earlier)
+		switch {
+		case x == -1:
+			return 1
+		case (Abs(x) < 1) == (y > 0):
+			return 0
+		default:
+			return Inf(1)
+		}
+	}
+
+	// ans = a1 * 2**ae (= 1 for now).
+	a1 := 1.0
+	ae := 0
+
+	// ans *= x**yf
+	if yf != 0 {
+		if yf > 0.5 {
+			yf--
+			yi++
+		}
+		a1 = Exp(yf * Log(x))
+	}
+
+	// ans *= x**yi
+	// by multiplying in successive squarings
+	// of x according to bits of yi.
+	// accumulate powers of two into exp.
+	x1, xe := Frexp(x)
+	for i := int64(yi); i != 0; i >>= 1 {
+		if xe < -1<<12 || 1<<12 < xe {
+			// catch xe before it overflows the left shift below
+			// Since i !=0 it has at least one bit still set, so ae will accumulate xe
+			// on at least one more iteration, ae += xe is a lower bound on ae
+			// the lower bound on ae exceeds the size of a float64 exp
+			// so the final call to Ldexp will produce under/overflow (0/Inf)
+			ae += xe
+			break
+		}
+		if i&1 == 1 {
+			a1 *= x1
+			ae += xe
+		}
+		x1 *= x1
+		xe <<= 1
+		if x1 < .5 {
+			x1 += x1
+			xe--
+		}
+	}
+
+	// ans = a1*2**ae
+	// if y < 0 { ans = 1 / ans }
+	// but in the opposite order
+	if y < 0 {
+		a1 = 1 / a1
+		ae = -ae
+	}
+	return Ldexp(a1, ae)
+}
diff --git a/contrib/go/_std_1.18/src/math/pow10.go b/contrib/go/_std_1.18/src/math/pow10.go
new file mode 100644
index 0000000000..1234e20885
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/pow10.go
@@ -0,0 +1,46 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// pow10tab stores the pre-computed values 10**i for i < 32.
+var pow10tab = [...]float64{
+	1e00, 1e01, 1e02, 1e03, 1e04, 1e05, 1e06, 1e07, 1e08, 1e09,
+	1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19,
+	1e20, 1e21, 1e22, 1e23, 1e24, 1e25, 1e26, 1e27, 1e28, 1e29,
+	1e30, 1e31,
+}
+
+// pow10postab32 stores the pre-computed value for 10**(i*32) at index i.
+var pow10postab32 = [...]float64{
+	1e00, 1e32, 1e64, 1e96, 1e128, 1e160, 1e192, 1e224, 1e256, 1e288,
+}
+
+// pow10negtab32 stores the pre-computed value for 10**(-i*32) at index i.
+var pow10negtab32 = [...]float64{
+	1e-00, 1e-32, 1e-64, 1e-96, 1e-128, 1e-160, 1e-192, 1e-224, 1e-256, 1e-288, 1e-320,
+}
+
+// Pow10 returns 10**n, the base-10 exponential of n.
+//
+// Special cases are:
+//	Pow10(n) =    0 for n < -323
+//	Pow10(n) = +Inf for n > 308
+func Pow10(n int) float64 {
+	if 0 <= n && n <= 308 {
+		return pow10postab32[uint(n)/32] * pow10tab[uint(n)%32]
+	}
+
+	if -323 <= n && n <= 0 {
+		return pow10negtab32[uint(-n)/32] / pow10tab[uint(-n)%32]
+	}
+
+	// n < -323 || 308 < n
+	if n > 0 {
+		return Inf(1)
+	}
+
+	// n < -323
+	return 0
+}
diff --git a/contrib/go/_std_1.18/src/math/rand/exp.go b/contrib/go/_std_1.18/src/math/rand/exp.go
new file mode 100644
index 0000000000..5a8d946c0c
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/rand/exp.go
@@ -0,0 +1,222 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package rand
+
+import (
+	"math"
+)
+
+/*
+ * Exponential distribution
+ *
+ * See "The Ziggurat Method for Generating Random Variables"
+ * (Marsaglia & Tsang, 2000)
+ * https://www.jstatsoft.org/v05/i08/paper [pdf]
+ */
+
+const (
+	re = 7.69711747013104972
+)
+
+// ExpFloat64 returns an exponentially distributed float64 in the range
+// (0, +math.MaxFloat64] with an exponential distribution whose rate parameter
+// (lambda) is 1 and whose mean is 1/lambda (1).
+// To produce a distribution with a different rate parameter,
+// callers can adjust the output using:
+//
+//  sample = ExpFloat64() / desiredRateParameter
+//
+func (r *Rand) ExpFloat64() float64 {
+	for {
+		j := r.Uint32()
+		i := j & 0xFF
+		x := float64(j) * float64(we[i])
+		if j < ke[i] {
+			return x
+		}
+		if i == 0 {
+			return re - math.Log(r.Float64())
+		}
+		if fe[i]+float32(r.Float64())*(fe[i-1]-fe[i]) < float32(math.Exp(-x)) {
+			return x
+		}
+	}
+}
+
+var ke = [256]uint32{
+	0xe290a139, 0x0, 0x9beadebc, 0xc377ac71, 0xd4ddb990,
+	0xde893fb8, 0xe4a8e87c, 0xe8dff16a, 0xebf2deab, 0xee49a6e8,
+	0xf0204efd, 0xf19bdb8e, 0xf2d458bb, 0xf3da104b, 0xf4b86d78,
+	0xf577ad8a, 0xf61de83d, 0xf6afb784, 0xf730a573, 0xf7a37651,
+	0xf80a5bb6, 0xf867189d, 0xf8bb1b4f, 0xf9079062, 0xf94d70ca,
+	0xf98d8c7d, 0xf9c8928a, 0xf9ff175b, 0xfa319996, 0xfa6085f8,
+	0xfa8c3a62, 0xfab5084e, 0xfadb36c8, 0xfaff0410, 0xfb20a6ea,
+	0xfb404fb4, 0xfb5e2951, 0xfb7a59e9, 0xfb95038c, 0xfbae44ba,
+	0xfbc638d8, 0xfbdcf892, 0xfbf29a30, 0xfc0731df, 0xfc1ad1ed,
+	0xfc2d8b02, 0xfc3f6c4d, 0xfc5083ac, 0xfc60ddd1, 0xfc708662,
+	0xfc7f8810, 0xfc8decb4, 0xfc9bbd62, 0xfca9027c, 0xfcb5c3c3,
+	0xfcc20864, 0xfccdd70a, 0xfcd935e3, 0xfce42ab0, 0xfceebace,
+	0xfcf8eb3b, 0xfd02c0a0, 0xfd0c3f59, 0xfd156b7b, 0xfd1e48d6,
+	0xfd26daff, 0xfd2f2552, 0xfd372af7, 0xfd3eeee5, 0xfd4673e7,
+	0xfd4dbc9e, 0xfd54cb85, 0xfd5ba2f2, 0xfd62451b, 0xfd68b415,
+	0xfd6ef1da, 0xfd750047, 0xfd7ae120, 0xfd809612, 0xfd8620b4,
+	0xfd8b8285, 0xfd90bcf5, 0xfd95d15e, 0xfd9ac10b, 0xfd9f8d36,
+	0xfda43708, 0xfda8bf9e, 0xfdad2806, 0xfdb17141, 0xfdb59c46,
+	0xfdb9a9fd, 0xfdbd9b46, 0xfdc170f6, 0xfdc52bd8, 0xfdc8ccac,
+	0xfdcc542d, 0xfdcfc30b, 0xfdd319ef, 0xfdd6597a, 0xfdd98245,
+	0xfddc94e5, 0xfddf91e6, 0xfde279ce, 0xfde54d1f, 0xfde80c52,
+	0xfdeab7de, 0xfded5034, 0xfdefd5be, 0xfdf248e3, 0xfdf4aa06,
+	0xfdf6f984, 0xfdf937b6, 0xfdfb64f4, 0xfdfd818d, 0xfdff8dd0,
+	0xfe018a08, 0xfe03767a, 0xfe05536c, 0xfe07211c, 0xfe08dfc9,
+	0xfe0a8fab, 0xfe0c30fb, 0xfe0dc3ec, 0xfe0f48b1, 0xfe10bf76,
+	0xfe122869, 0xfe1383b4, 0xfe14d17c, 0xfe1611e7, 0xfe174516,
+	0xfe186b2a, 0xfe19843e, 0xfe1a9070, 0xfe1b8fd6, 0xfe1c8289,
+	0xfe1d689b, 0xfe1e4220, 0xfe1f0f26, 0xfe1fcfbc, 0xfe2083ed,
+	0xfe212bc3, 0xfe21c745, 0xfe225678, 0xfe22d95f, 0xfe234ffb,
+	0xfe23ba4a, 0xfe241849, 0xfe2469f2, 0xfe24af3c, 0xfe24e81e,
+	0xfe25148b, 0xfe253474, 0xfe2547c7, 0xfe254e70, 0xfe25485a,
+	0xfe25356a, 0xfe251586, 0xfe24e88f, 0xfe24ae64, 0xfe2466e1,
+	0xfe2411df, 0xfe23af34, 0xfe233eb4, 0xfe22c02c, 0xfe22336b,
+	0xfe219838, 0xfe20ee58, 0xfe20358c, 0xfe1f6d92, 0xfe1e9621,
+	0xfe1daef0, 0xfe1cb7ac, 0xfe1bb002, 0xfe1a9798, 0xfe196e0d,
+	0xfe1832fd, 0xfe16e5fe, 0xfe15869d, 0xfe141464, 0xfe128ed3,
+	0xfe10f565, 0xfe0f478c, 0xfe0d84b1, 0xfe0bac36, 0xfe09bd73,
+	0xfe07b7b5, 0xfe059a40, 0xfe03644c, 0xfe011504, 0xfdfeab88,
+	0xfdfc26e9, 0xfdf98629, 0xfdf6c83b, 0xfdf3ec01, 0xfdf0f04a,
+	0xfdedd3d1, 0xfdea953d, 0xfde7331e, 0xfde3abe9, 0xfddffdfb,
+	0xfddc2791, 0xfdd826cd, 0xfdd3f9a8, 0xfdcf9dfc, 0xfdcb1176,
+	0xfdc65198, 0xfdc15bb3, 0xfdbc2ce2, 0xfdb6c206, 0xfdb117be,
+	0xfdab2a63, 0xfda4f5fd, 0xfd9e7640, 0xfd97a67a, 0xfd908192,
+	0xfd8901f2, 0xfd812182, 0xfd78d98e, 0xfd7022bb, 0xfd66f4ed,
+	0xfd5d4732, 0xfd530f9c, 0xfd48432b, 0xfd3cd59a, 0xfd30b936,
+	0xfd23dea4, 0xfd16349e, 0xfd07a7a3, 0xfcf8219b, 0xfce7895b,
+	0xfcd5c220, 0xfcc2aadb, 0xfcae1d5e, 0xfc97ed4e, 0xfc7fe6d4,
+	0xfc65ccf3, 0xfc495762, 0xfc2a2fc8, 0xfc07ee19, 0xfbe213c1,
+	0xfbb8051a, 0xfb890078, 0xfb5411a5, 0xfb180005, 0xfad33482,
+	0xfa839276, 0xfa263b32, 0xf9b72d1c, 0xf930a1a2, 0xf889f023,
+	0xf7b577d2, 0xf69c650c, 0xf51530f0, 0xf2cb0e3c, 0xeeefb15d,
+	0xe6da6ecf,
+}
+var we = [256]float32{
+	2.0249555e-09, 1.486674e-11, 2.4409617e-11, 3.1968806e-11,
+	3.844677e-11, 4.4228204e-11, 4.9516443e-11, 5.443359e-11,
+	5.905944e-11, 6.344942e-11, 6.7643814e-11, 7.1672945e-11,
+	7.556032e-11, 7.932458e-11, 8.298079e-11, 8.654132e-11,
+	9.0016515e-11, 9.3415074e-11, 9.674443e-11, 1.0001099e-10,
+	1.03220314e-10, 1.06377254e-10, 1.09486115e-10, 1.1255068e-10,
+	1.1557435e-10, 1.1856015e-10, 1.2151083e-10, 1.2442886e-10,
+	1.2731648e-10, 1.3017575e-10, 1.3300853e-10, 1.3581657e-10,
+	1.3860142e-10, 1.4136457e-10, 1.4410738e-10, 1.4683108e-10,
+	1.4953687e-10, 1.5222583e-10, 1.54899e-10, 1.5755733e-10,
+	1.6020171e-10, 1.6283301e-10, 1.6545203e-10, 1.6805951e-10,
+	1.7065617e-10, 1.732427e-10, 1.7581973e-10, 1.7838787e-10,
+	1.8094774e-10, 1.8349985e-10, 1.8604476e-10, 1.8858298e-10,
+	1.9111498e-10, 1.9364126e-10, 1.9616223e-10, 1.9867835e-10,
+	2.0119004e-10, 2.0369768e-10, 2.0620168e-10, 2.087024e-10,
+	2.1120022e-10, 2.136955e-10, 2.1618855e-10, 2.1867974e-10,
+	2.2116936e-10, 2.2365775e-10, 2.261452e-10, 2.2863202e-10,
+	2.311185e-10, 2.3360494e-10, 2.360916e-10, 2.3857874e-10,
+	2.4106667e-10, 2.4355562e-10, 2.4604588e-10, 2.485377e-10,
+	2.5103128e-10, 2.5352695e-10, 2.560249e-10, 2.585254e-10,
+	2.6102867e-10, 2.6353494e-10, 2.6604446e-10, 2.6855745e-10,
+	2.7107416e-10, 2.7359479e-10, 2.761196e-10, 2.7864877e-10,
+	2.8118255e-10, 2.8372119e-10, 2.8626485e-10, 2.888138e-10,
+	2.9136826e-10, 2.939284e-10, 2.9649452e-10, 2.9906677e-10,
+	3.016454e-10, 3.0423064e-10, 3.0682268e-10, 3.0942177e-10,
+	3.1202813e-10, 3.1464195e-10, 3.1726352e-10, 3.19893e-10,
+	3.2253064e-10, 3.251767e-10, 3.2783135e-10, 3.3049485e-10,
+	3.3316744e-10, 3.3584938e-10, 3.3854083e-10, 3.4124212e-10,
+	3.4395342e-10, 3.46675e-10, 3.4940711e-10, 3.5215003e-10,
+	3.5490397e-10, 3.5766917e-10, 3.6044595e-10, 3.6323455e-10,
+	3.660352e-10, 3.6884823e-10, 3.7167386e-10, 3.745124e-10,
+	3.773641e-10, 3.802293e-10, 3.8310827e-10, 3.860013e-10,
+	3.8890866e-10, 3.918307e-10, 3.9476775e-10, 3.9772008e-10,
+	4.0068804e-10, 4.0367196e-10, 4.0667217e-10, 4.09689e-10,
+	4.1272286e-10, 4.1577405e-10, 4.1884296e-10, 4.2192994e-10,
+	4.250354e-10, 4.281597e-10, 4.313033e-10, 4.3446652e-10,
+	4.3764986e-10, 4.408537e-10, 4.4407847e-10, 4.4732465e-10,
+	4.5059267e-10, 4.5388301e-10, 4.571962e-10, 4.6053267e-10,
+	4.6389292e-10, 4.6727755e-10, 4.70687e-10, 4.741219e-10,
+	4.7758275e-10, 4.810702e-10, 4.845848e-10, 4.8812715e-10,
+	4.9169796e-10, 4.9529775e-10, 4.989273e-10, 5.0258725e-10,
+	5.0627835e-10, 5.100013e-10, 5.1375687e-10, 5.1754584e-10,
+	5.21369e-10, 5.2522725e-10, 5.2912136e-10, 5.330522e-10,
+	5.370208e-10, 5.4102806e-10, 5.45075e-10, 5.491625e-10,
+	5.532918e-10, 5.5746385e-10, 5.616799e-10, 5.6594107e-10,
+	5.7024857e-10, 5.746037e-10, 5.7900773e-10, 5.834621e-10,
+	5.8796823e-10, 5.925276e-10, 5.971417e-10, 6.018122e-10,
+	6.065408e-10, 6.113292e-10, 6.1617933e-10, 6.2109295e-10,
+	6.260722e-10, 6.3111916e-10, 6.3623595e-10, 6.4142497e-10,
+	6.4668854e-10, 6.5202926e-10, 6.5744976e-10, 6.6295286e-10,
+	6.6854156e-10, 6.742188e-10, 6.79988e-10, 6.858526e-10,
+	6.9181616e-10, 6.978826e-10, 7.04056e-10, 7.103407e-10,
+	7.167412e-10, 7.2326256e-10, 7.2990985e-10, 7.366886e-10,
+	7.4360473e-10, 7.5066453e-10, 7.5787476e-10, 7.6524265e-10,
+	7.7277595e-10, 7.80483e-10, 7.883728e-10, 7.9645507e-10,
+	8.047402e-10, 8.1323964e-10, 8.219657e-10, 8.309319e-10,
+	8.401528e-10, 8.496445e-10, 8.594247e-10, 8.6951274e-10,
+	8.799301e-10, 8.9070046e-10, 9.018503e-10, 9.134092e-10,
+	9.254101e-10, 9.378904e-10, 9.508923e-10, 9.644638e-10,
+	9.786603e-10, 9.935448e-10, 1.0091913e-09, 1.025686e-09,
+	1.0431306e-09, 1.0616465e-09, 1.08138e-09, 1.1025096e-09,
+	1.1252564e-09, 1.1498986e-09, 1.1767932e-09, 1.206409e-09,
+	1.2393786e-09, 1.276585e-09, 1.3193139e-09, 1.3695435e-09,
+	1.4305498e-09, 1.508365e-09, 1.6160854e-09, 1.7921248e-09,
+}
+var fe = [256]float32{
+	1, 0.9381437, 0.90046996, 0.87170434, 0.8477855, 0.8269933,
+	0.8084217, 0.7915276, 0.77595687, 0.7614634, 0.7478686,
+	0.7350381, 0.72286767, 0.71127474, 0.70019263, 0.6895665,
+	0.67935055, 0.6695063, 0.66000086, 0.65080583, 0.6418967,
+	0.63325197, 0.6248527, 0.6166822, 0.60872537, 0.60096896,
+	0.5934009, 0.58601034, 0.5787874, 0.57172304, 0.5648092,
+	0.5580383, 0.5514034, 0.5448982, 0.5385169, 0.53225386,
+	0.5261042, 0.52006316, 0.5141264, 0.50828975, 0.5025495,
+	0.496902, 0.49134386, 0.485872, 0.48048335, 0.4751752,
+	0.46994483, 0.46478975, 0.45970762, 0.45469615, 0.44975325,
+	0.44487688, 0.44006512, 0.43531612, 0.43062815, 0.42599955,
+	0.42142874, 0.4169142, 0.41245446, 0.40804818, 0.403694,
+	0.3993907, 0.39513698, 0.39093173, 0.38677382, 0.38266218,
+	0.37859577, 0.37457356, 0.37059465, 0.3666581, 0.362763,
+	0.35890847, 0.35509375, 0.351318, 0.3475805, 0.34388044,
+	0.34021714, 0.3365899, 0.33299807, 0.32944095, 0.32591796,
+	0.3224285, 0.3189719, 0.31554767, 0.31215525, 0.30879408,
+	0.3054636, 0.3021634, 0.29889292, 0.2956517, 0.29243928,
+	0.28925523, 0.28609908, 0.28297043, 0.27986884, 0.27679393,
+	0.2737453, 0.2707226, 0.2677254, 0.26475343, 0.26180625,
+	0.25888354, 0.25598502, 0.2531103, 0.25025907, 0.24743107,
+	0.24462597, 0.24184346, 0.23908329, 0.23634516, 0.23362878,
+	0.23093392, 0.2282603, 0.22560766, 0.22297576, 0.22036438,
+	0.21777324, 0.21520215, 0.21265087, 0.21011916, 0.20760682,
+	0.20511365, 0.20263945, 0.20018397, 0.19774707, 0.19532852,
+	0.19292815, 0.19054577, 0.1881812, 0.18583426, 0.18350479,
+	0.1811926, 0.17889754, 0.17661946, 0.17435817, 0.17211354,
+	0.1698854, 0.16767362, 0.16547804, 0.16329853, 0.16113494,
+	0.15898713, 0.15685499, 0.15473837, 0.15263714, 0.15055119,
+	0.14848037, 0.14642459, 0.14438373, 0.14235765, 0.14034624,
+	0.13834943, 0.13636707, 0.13439907, 0.13244532, 0.13050574,
+	0.1285802, 0.12666863, 0.12477092, 0.12288698, 0.12101672,
+	0.119160056, 0.1173169, 0.115487166, 0.11367077, 0.11186763,
+	0.11007768, 0.10830083, 0.10653701, 0.10478614, 0.10304816,
+	0.101323, 0.09961058, 0.09791085, 0.09622374, 0.09454919,
+	0.09288713, 0.091237515, 0.08960028, 0.087975375, 0.08636274,
+	0.08476233, 0.083174095, 0.081597984, 0.08003395, 0.07848195,
+	0.076941945, 0.07541389, 0.07389775, 0.072393484, 0.07090106,
+	0.069420435, 0.06795159, 0.066494495, 0.06504912, 0.063615434,
+	0.062193416, 0.060783047, 0.059384305, 0.057997175,
+	0.05662164, 0.05525769, 0.053905312, 0.052564494, 0.051235236,
+	0.049917534, 0.048611384, 0.047316793, 0.046033762, 0.0447623,
+	0.043502413, 0.042254124, 0.041017443, 0.039792392,
+	0.038578995, 0.037377283, 0.036187284, 0.035009038,
+	0.033842582, 0.032687962, 0.031545233, 0.030414443, 0.02929566,
+	0.02818895, 0.027094385, 0.026012046, 0.024942026, 0.023884421,
+	0.022839336, 0.021806888, 0.020787204, 0.019780423, 0.0187867,
+	0.0178062, 0.016839107, 0.015885621, 0.014945968, 0.014020392,
+	0.013109165, 0.012212592, 0.011331013, 0.01046481, 0.009614414,
+	0.008780315, 0.007963077, 0.0071633533, 0.006381906,
+	0.0056196423, 0.0048776558, 0.004157295, 0.0034602648,
+	0.0027887989, 0.0021459677, 0.0015362998, 0.0009672693,
+	0.00045413437,
+}
diff --git a/contrib/go/_std_1.18/src/math/rand/normal.go b/contrib/go/_std_1.18/src/math/rand/normal.go
new file mode 100644
index 0000000000..2c5a7aa99b
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/rand/normal.go
@@ -0,0 +1,157 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package rand
+
+import (
+	"math"
+)
+
+/*
+ * Normal distribution
+ *
+ * See "The Ziggurat Method for Generating Random Variables"
+ * (Marsaglia & Tsang, 2000)
+ * http://www.jstatsoft.org/v05/i08/paper [pdf]
+ */
+
+const (
+	rn = 3.442619855899
+)
+
+func absInt32(i int32) uint32 {
+	if i < 0 {
+		return uint32(-i)
+	}
+	return uint32(i)
+}
+
+// NormFloat64 returns a normally distributed float64 in
+// the range -math.MaxFloat64 through +math.MaxFloat64 inclusive,
+// with standard normal distribution (mean = 0, stddev = 1).
+// To produce a different normal distribution, callers can
+// adjust the output using:
+//
+//  sample = NormFloat64() * desiredStdDev + desiredMean
+//
+func (r *Rand) NormFloat64() float64 {
+	for {
+		j := int32(r.Uint32()) // Possibly negative
+		i := j & 0x7F
+		x := float64(j) * float64(wn[i])
+		if absInt32(j) < kn[i] {
+			// This case should be hit better than 99% of the time.
+			return x
+		}
+
+		if i == 0 {
+			// This extra work is only required for the base strip.
+			for {
+				x = -math.Log(r.Float64()) * (1.0 / rn)
+				y := -math.Log(r.Float64())
+				if y+y >= x*x {
+					break
+				}
+			}
+			if j > 0 {
+				return rn + x
+			}
+			return -rn - x
+		}
+		if fn[i]+float32(r.Float64())*(fn[i-1]-fn[i]) < float32(math.Exp(-.5*x*x)) {
+			return x
+		}
+	}
+}
+
+var kn = [128]uint32{
+	0x76ad2212, 0x0, 0x600f1b53, 0x6ce447a6, 0x725b46a2,
+	0x7560051d, 0x774921eb, 0x789a25bd, 0x799045c3, 0x7a4bce5d,
+	0x7adf629f, 0x7b5682a6, 0x7bb8a8c6, 0x7c0ae722, 0x7c50cce7,
+	0x7c8cec5b, 0x7cc12cd6, 0x7ceefed2, 0x7d177e0b, 0x7d3b8883,
+	0x7d5bce6c, 0x7d78dd64, 0x7d932886, 0x7dab0e57, 0x7dc0dd30,
+	0x7dd4d688, 0x7de73185, 0x7df81cea, 0x7e07c0a3, 0x7e163efa,
+	0x7e23b587, 0x7e303dfd, 0x7e3beec2, 0x7e46db77, 0x7e51155d,
+	0x7e5aabb3, 0x7e63abf7, 0x7e6c222c, 0x7e741906, 0x7e7b9a18,
+	0x7e82adfa, 0x7e895c63, 0x7e8fac4b, 0x7e95a3fb, 0x7e9b4924,
+	0x7ea0a0ef, 0x7ea5b00d, 0x7eaa7ac3, 0x7eaf04f3, 0x7eb3522a,
+	0x7eb765a5, 0x7ebb4259, 0x7ebeeafd, 0x7ec2620a, 0x7ec5a9c4,
+	0x7ec8c441, 0x7ecbb365, 0x7ece78ed, 0x7ed11671, 0x7ed38d62,
+	0x7ed5df12, 0x7ed80cb4, 0x7eda175c, 0x7edc0005, 0x7eddc78e,
+	0x7edf6ebf, 0x7ee0f647, 0x7ee25ebe, 0x7ee3a8a9, 0x7ee4d473,
+	0x7ee5e276, 0x7ee6d2f5, 0x7ee7a620, 0x7ee85c10, 0x7ee8f4cd,
+	0x7ee97047, 0x7ee9ce59, 0x7eea0eca, 0x7eea3147, 0x7eea3568,
+	0x7eea1aab, 0x7ee9e071, 0x7ee98602, 0x7ee90a88, 0x7ee86d08,
+	0x7ee7ac6a, 0x7ee6c769, 0x7ee5bc9c, 0x7ee48a67, 0x7ee32efc,
+	0x7ee1a857, 0x7edff42f, 0x7ede0ffa, 0x7edbf8d9, 0x7ed9ab94,
+	0x7ed7248d, 0x7ed45fae, 0x7ed1585c, 0x7ece095f, 0x7eca6ccb,
+	0x7ec67be2, 0x7ec22eee, 0x7ebd7d1a, 0x7eb85c35, 0x7eb2c075,
+	0x7eac9c20, 0x7ea5df27, 0x7e9e769f, 0x7e964c16, 0x7e8d44ba,
+	0x7e834033, 0x7e781728, 0x7e6b9933, 0x7e5d8a1a, 0x7e4d9ded,
+	0x7e3b737a, 0x7e268c2f, 0x7e0e3ff5, 0x7df1aa5d, 0x7dcf8c72,
+	0x7da61a1e, 0x7d72a0fb, 0x7d30e097, 0x7cd9b4ab, 0x7c600f1a,
+	0x7ba90bdc, 0x7a722176, 0x77d664e5,
+}
+var wn = [128]float32{
+	1.7290405e-09, 1.2680929e-10, 1.6897518e-10, 1.9862688e-10,
+	2.2232431e-10, 2.4244937e-10, 2.601613e-10, 2.7611988e-10,
+	2.9073963e-10, 3.042997e-10, 3.1699796e-10, 3.289802e-10,
+	3.4035738e-10, 3.5121603e-10, 3.616251e-10, 3.7164058e-10,
+	3.8130857e-10, 3.9066758e-10, 3.9975012e-10, 4.08584e-10,
+	4.1719309e-10, 4.2559822e-10, 4.338176e-10, 4.418672e-10,
+	4.497613e-10, 4.5751258e-10, 4.651324e-10, 4.7263105e-10,
+	4.8001775e-10, 4.87301e-10, 4.944885e-10, 5.015873e-10,
+	5.0860405e-10, 5.155446e-10, 5.2241467e-10, 5.2921934e-10,
+	5.359635e-10, 5.426517e-10, 5.4928817e-10, 5.5587696e-10,
+	5.624219e-10, 5.6892646e-10, 5.753941e-10, 5.818282e-10,
+	5.882317e-10, 5.946077e-10, 6.00959e-10, 6.072884e-10,
+	6.135985e-10, 6.19892e-10, 6.2617134e-10, 6.3243905e-10,
+	6.386974e-10, 6.449488e-10, 6.511956e-10, 6.5744005e-10,
+	6.6368433e-10, 6.699307e-10, 6.7618144e-10, 6.824387e-10,
+	6.8870465e-10, 6.949815e-10, 7.012715e-10, 7.075768e-10,
+	7.1389966e-10, 7.202424e-10, 7.266073e-10, 7.329966e-10,
+	7.394128e-10, 7.4585826e-10, 7.5233547e-10, 7.58847e-10,
+	7.653954e-10, 7.719835e-10, 7.7861395e-10, 7.852897e-10,
+	7.920138e-10, 7.987892e-10, 8.0561924e-10, 8.125073e-10,
+	8.194569e-10, 8.2647167e-10, 8.3355556e-10, 8.407127e-10,
+	8.479473e-10, 8.55264e-10, 8.6266755e-10, 8.7016316e-10,
+	8.777562e-10, 8.8545243e-10, 8.932582e-10, 9.0117996e-10,
+	9.09225e-10, 9.174008e-10, 9.2571584e-10, 9.341788e-10,
+	9.427997e-10, 9.515889e-10, 9.605579e-10, 9.697193e-10,
+	9.790869e-10, 9.88676e-10, 9.985036e-10, 1.0085882e-09,
+	1.0189509e-09, 1.0296151e-09, 1.0406069e-09, 1.0519566e-09,
+	1.063698e-09, 1.0758702e-09, 1.0885183e-09, 1.1016947e-09,
+	1.1154611e-09, 1.1298902e-09, 1.1450696e-09, 1.1611052e-09,
+	1.1781276e-09, 1.1962995e-09, 1.2158287e-09, 1.2369856e-09,
+	1.2601323e-09, 1.2857697e-09, 1.3146202e-09, 1.347784e-09,
+	1.3870636e-09, 1.4357403e-09, 1.5008659e-09, 1.6030948e-09,
+}
+var fn = [128]float32{
+	1, 0.9635997, 0.9362827, 0.9130436, 0.89228165, 0.87324303,
+	0.8555006, 0.8387836, 0.8229072, 0.8077383, 0.793177,
+	0.7791461, 0.7655842, 0.7524416, 0.73967725, 0.7272569,
+	0.7151515, 0.7033361, 0.69178915, 0.68049186, 0.6694277,
+	0.658582, 0.6479418, 0.63749546, 0.6272325, 0.6171434,
+	0.6072195, 0.5974532, 0.58783704, 0.5783647, 0.56903,
+	0.5598274, 0.5507518, 0.54179835, 0.5329627, 0.52424055,
+	0.5156282, 0.50712204, 0.49871865, 0.49041483, 0.48220766,
+	0.4740943, 0.46607214, 0.4581387, 0.45029163, 0.44252872,
+	0.43484783, 0.427247, 0.41972435, 0.41227803, 0.40490642,
+	0.39760786, 0.3903808, 0.3832238, 0.37613547, 0.36911446,
+	0.3621595, 0.35526937, 0.34844297, 0.34167916, 0.33497685,
+	0.3283351, 0.3217529, 0.3152294, 0.30876362, 0.30235484,
+	0.29600215, 0.28970486, 0.2834622, 0.2772735, 0.27113807,
+	0.2650553, 0.25902456, 0.2530453, 0.24711695, 0.241239,
+	0.23541094, 0.22963232, 0.2239027, 0.21822165, 0.21258877,
+	0.20700371, 0.20146611, 0.19597565, 0.19053204, 0.18513499,
+	0.17978427, 0.17447963, 0.1692209, 0.16400786, 0.15884037,
+	0.15371831, 0.14864157, 0.14361008, 0.13862377, 0.13368265,
+	0.12878671, 0.12393598, 0.119130544, 0.11437051, 0.10965602,
+	0.104987256, 0.10036444, 0.095787846, 0.0912578, 0.08677467,
+	0.0823389, 0.077950984, 0.073611505, 0.06932112, 0.06508058,
+	0.06089077, 0.056752663, 0.0526674, 0.048636295, 0.044660863,
+	0.040742867, 0.03688439, 0.033087887, 0.029356318,
+	0.025693292, 0.022103304, 0.018592102, 0.015167298,
+	0.011839478, 0.008624485, 0.005548995, 0.0026696292,
+}
diff --git a/contrib/go/_std_1.18/src/math/rand/rand.go b/contrib/go/_std_1.18/src/math/rand/rand.go
new file mode 100644
index 0000000000..13f20ca5ef
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/rand/rand.go
@@ -0,0 +1,421 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package rand implements pseudo-random number generators unsuitable for
+// security-sensitive work.
+//
+// Random numbers are generated by a Source. Top-level functions, such as
+// Float64 and Int, use a default shared Source that produces a deterministic
+// sequence of values each time a program is run. Use the Seed function to
+// initialize the default Source if different behavior is required for each run.
+// The default Source is safe for concurrent use by multiple goroutines, but
+// Sources created by NewSource are not.
+//
+// This package's outputs might be easily predictable regardless of how it's
+// seeded. For random numbers suitable for security-sensitive work, see the
+// crypto/rand package.
+package rand
+
+import "sync"
+
+// A Source represents a source of uniformly-distributed
+// pseudo-random int64 values in the range [0, 1<<63).
+type Source interface {
+	Int63() int64
+	Seed(seed int64)
+}
+
+// A Source64 is a Source that can also generate
+// uniformly-distributed pseudo-random uint64 values in
+// the range [0, 1<<64) directly.
+// If a Rand r's underlying Source s implements Source64,
+// then r.Uint64 returns the result of one call to s.Uint64
+// instead of making two calls to s.Int63.
+type Source64 interface {
+	Source
+	Uint64() uint64
+}
+
+// NewSource returns a new pseudo-random Source seeded with the given value.
+// Unlike the default Source used by top-level functions, this source is not
+// safe for concurrent use by multiple goroutines.
+func NewSource(seed int64) Source {
+	var rng rngSource
+	rng.Seed(seed)
+	return &rng
+}
+
+// A Rand is a source of random numbers.
+type Rand struct {
+	src Source
+	s64 Source64 // non-nil if src is source64
+
+	// readVal contains remainder of 63-bit integer used for bytes
+	// generation during most recent Read call.
+	// It is saved so next Read call can start where the previous
+	// one finished.
+	readVal int64
+	// readPos indicates the number of low-order bytes of readVal
+	// that are still valid.
+	readPos int8
+}
+
+// New returns a new Rand that uses random values from src
+// to generate other random values.
+func New(src Source) *Rand {
+	s64, _ := src.(Source64)
+	return &Rand{src: src, s64: s64}
+}
+
+// Seed uses the provided seed value to initialize the generator to a deterministic state.
+// Seed should not be called concurrently with any other Rand method.
+func (r *Rand) Seed(seed int64) {
+	if lk, ok := r.src.(*lockedSource); ok {
+		lk.seedPos(seed, &r.readPos)
+		return
+	}
+
+	r.src.Seed(seed)
+	r.readPos = 0
+}
+
+// Int63 returns a non-negative pseudo-random 63-bit integer as an int64.
+func (r *Rand) Int63() int64 { return r.src.Int63() }
+
+// Uint32 returns a pseudo-random 32-bit value as a uint32.
+func (r *Rand) Uint32() uint32 { return uint32(r.Int63() >> 31) }
+
+// Uint64 returns a pseudo-random 64-bit value as a uint64.
+func (r *Rand) Uint64() uint64 {
+	if r.s64 != nil {
+		return r.s64.Uint64()
+	}
+	return uint64(r.Int63())>>31 | uint64(r.Int63())<<32
+}
+
+// Int31 returns a non-negative pseudo-random 31-bit integer as an int32.
+func (r *Rand) Int31() int32 { return int32(r.Int63() >> 32) }
+
+// Int returns a non-negative pseudo-random int.
+func (r *Rand) Int() int {
+	u := uint(r.Int63())
+	return int(u << 1 >> 1) // clear sign bit if int == int32
+}
+
+// Int63n returns, as an int64, a non-negative pseudo-random number in the half-open interval [0,n).
+// It panics if n <= 0.
+func (r *Rand) Int63n(n int64) int64 {
+	if n <= 0 {
+		panic("invalid argument to Int63n")
+	}
+	if n&(n-1) == 0 { // n is power of two, can mask
+		return r.Int63() & (n - 1)
+	}
+	max := int64((1 << 63) - 1 - (1<<63)%uint64(n))
+	v := r.Int63()
+	for v > max {
+		v = r.Int63()
+	}
+	return v % n
+}
+
+// Int31n returns, as an int32, a non-negative pseudo-random number in the half-open interval [0,n).
+// It panics if n <= 0.
+func (r *Rand) Int31n(n int32) int32 {
+	if n <= 0 {
+		panic("invalid argument to Int31n")
+	}
+	if n&(n-1) == 0 { // n is power of two, can mask
+		return r.Int31() & (n - 1)
+	}
+	max := int32((1 << 31) - 1 - (1<<31)%uint32(n))
+	v := r.Int31()
+	for v > max {
+		v = r.Int31()
+	}
+	return v % n
+}
+
+// int31n returns, as an int32, a non-negative pseudo-random number in the half-open interval [0,n).
+// n must be > 0, but int31n does not check this; the caller must ensure it.
+// int31n exists because Int31n is inefficient, but Go 1 compatibility
+// requires that the stream of values produced by math/rand remain unchanged.
+// int31n can thus only be used internally, by newly introduced APIs.
+//
+// For implementation details, see:
+// https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction
+// https://lemire.me/blog/2016/06/30/fast-random-shuffling
+func (r *Rand) int31n(n int32) int32 {
+	v := r.Uint32()
+	prod := uint64(v) * uint64(n)
+	low := uint32(prod)
+	if low < uint32(n) {
+		thresh := uint32(-n) % uint32(n)
+		for low < thresh {
+			v = r.Uint32()
+			prod = uint64(v) * uint64(n)
+			low = uint32(prod)
+		}
+	}
+	return int32(prod >> 32)
+}
+
+// Intn returns, as an int, a non-negative pseudo-random number in the half-open interval [0,n).
+// It panics if n <= 0.
+func (r *Rand) Intn(n int) int {
+	if n <= 0 {
+		panic("invalid argument to Intn")
+	}
+	if n <= 1<<31-1 {
+		return int(r.Int31n(int32(n)))
+	}
+	return int(r.Int63n(int64(n)))
+}
+
+// Float64 returns, as a float64, a pseudo-random number in the half-open interval [0.0,1.0).
+func (r *Rand) Float64() float64 {
+	// A clearer, simpler implementation would be:
+	//	return float64(r.Int63n(1<<53)) / (1<<53)
+	// However, Go 1 shipped with
+	//	return float64(r.Int63()) / (1 << 63)
+	// and we want to preserve that value stream.
+	//
+	// There is one bug in the value stream: r.Int63() may be so close
+	// to 1<<63 that the division rounds up to 1.0, and we've guaranteed
+	// that the result is always less than 1.0.
+	//
+	// We tried to fix this by mapping 1.0 back to 0.0, but since float64
+	// values near 0 are much denser than near 1, mapping 1 to 0 caused
+	// a theoretically significant overshoot in the probability of returning 0.
+	// Instead of that, if we round up to 1, just try again.
+	// Getting 1 only happens 1/2⁵³ of the time, so most clients
+	// will not observe it anyway.
+again:
+	f := float64(r.Int63()) / (1 << 63)
+	if f == 1 {
+		goto again // resample; this branch is taken O(never)
+	}
+	return f
+}
+
+// Float32 returns, as a float32, a pseudo-random number in the half-open interval [0.0,1.0).
+func (r *Rand) Float32() float32 {
+	// Same rationale as in Float64: we want to preserve the Go 1 value
+	// stream except we want to fix it not to return 1.0
+	// This only happens 1/2²⁴ of the time (plus the 1/2⁵³ of the time in Float64).
+again:
+	f := float32(r.Float64())
+	if f == 1 {
+		goto again // resample; this branch is taken O(very rarely)
+	}
+	return f
+}
+
+// Perm returns, as a slice of n ints, a pseudo-random permutation of the integers
+// in the half-open interval [0,n).
+func (r *Rand) Perm(n int) []int {
+	m := make([]int, n)
+	// In the following loop, the iteration when i=0 always swaps m[0] with m[0].
+	// A change to remove this useless iteration is to assign 1 to i in the init
+	// statement. But Perm also effects r. Making this change will affect
+	// the final state of r. So this change can't be made for compatibility
+	// reasons for Go 1.
+	for i := 0; i < n; i++ {
+		j := r.Intn(i + 1)
+		m[i] = m[j]
+		m[j] = i
+	}
+	return m
+}
+
+// Shuffle pseudo-randomizes the order of elements.
+// n is the number of elements. Shuffle panics if n < 0.
+// swap swaps the elements with indexes i and j.
+func (r *Rand) Shuffle(n int, swap func(i, j int)) {
+	if n < 0 {
+		panic("invalid argument to Shuffle")
+	}
+
+	// Fisher-Yates shuffle: https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
+	// Shuffle really ought not be called with n that doesn't fit in 32 bits.
+	// Not only will it take a very long time, but with 2³¹! possible permutations,
+	// there's no way that any PRNG can have a big enough internal state to
+	// generate even a minuscule percentage of the possible permutations.
+	// Nevertheless, the right API signature accepts an int n, so handle it as best we can.
+	i := n - 1
+	for ; i > 1<<31-1-1; i-- {
+		j := int(r.Int63n(int64(i + 1)))
+		swap(i, j)
+	}
+	for ; i > 0; i-- {
+		j := int(r.int31n(int32(i + 1)))
+		swap(i, j)
+	}
+}
+
+// Read generates len(p) random bytes and writes them into p. It
+// always returns len(p) and a nil error.
+// Read should not be called concurrently with any other Rand method.
+func (r *Rand) Read(p []byte) (n int, err error) {
+	if lk, ok := r.src.(*lockedSource); ok {
+		return lk.read(p, &r.readVal, &r.readPos)
+	}
+	return read(p, r.src, &r.readVal, &r.readPos)
+}
+
+func read(p []byte, src Source, readVal *int64, readPos *int8) (n int, err error) {
+	pos := *readPos
+	val := *readVal
+	rng, _ := src.(*rngSource)
+	for n = 0; n < len(p); n++ {
+		if pos == 0 {
+			if rng != nil {
+				val = rng.Int63()
+			} else {
+				val = src.Int63()
+			}
+			pos = 7
+		}
+		p[n] = byte(val)
+		val >>= 8
+		pos--
+	}
+	*readPos = pos
+	*readVal = val
+	return
+}
+
+/*
+ * Top-level convenience functions
+ */
+
+var globalRand = New(&lockedSource{src: NewSource(1).(*rngSource)})
+
+// Type assert that globalRand's source is a lockedSource whose src is a *rngSource.
+var _ *rngSource = globalRand.src.(*lockedSource).src
+
+// Seed uses the provided seed value to initialize the default Source to a
+// deterministic state. If Seed is not called, the generator behaves as
+// if seeded by Seed(1). Seed values that have the same remainder when
+// divided by 2³¹-1 generate the same pseudo-random sequence.
+// Seed, unlike the Rand.Seed method, is safe for concurrent use.
+func Seed(seed int64) { globalRand.Seed(seed) }
+
+// Int63 returns a non-negative pseudo-random 63-bit integer as an int64
+// from the default Source.
+func Int63() int64 { return globalRand.Int63() }
+
+// Uint32 returns a pseudo-random 32-bit value as a uint32
+// from the default Source.
+func Uint32() uint32 { return globalRand.Uint32() }
+
+// Uint64 returns a pseudo-random 64-bit value as a uint64
+// from the default Source.
+func Uint64() uint64 { return globalRand.Uint64() }
+
+// Int31 returns a non-negative pseudo-random 31-bit integer as an int32
+// from the default Source.
+func Int31() int32 { return globalRand.Int31() }
+
+// Int returns a non-negative pseudo-random int from the default Source.
+func Int() int { return globalRand.Int() }
+
+// Int63n returns, as an int64, a non-negative pseudo-random number in the half-open interval [0,n)
+// from the default Source.
+// It panics if n <= 0.
+func Int63n(n int64) int64 { return globalRand.Int63n(n) }
+
+// Int31n returns, as an int32, a non-negative pseudo-random number in the half-open interval [0,n)
+// from the default Source.
+// It panics if n <= 0.
+func Int31n(n int32) int32 { return globalRand.Int31n(n) }
+
+// Intn returns, as an int, a non-negative pseudo-random number in the half-open interval [0,n)
+// from the default Source.
+// It panics if n <= 0.
+func Intn(n int) int { return globalRand.Intn(n) }
+
+// Float64 returns, as a float64, a pseudo-random number in the half-open interval [0.0,1.0)
+// from the default Source.
+func Float64() float64 { return globalRand.Float64() }
+
+// Float32 returns, as a float32, a pseudo-random number in the half-open interval [0.0,1.0)
+// from the default Source.
+func Float32() float32 { return globalRand.Float32() }
+
+// Perm returns, as a slice of n ints, a pseudo-random permutation of the integers
+// in the half-open interval [0,n) from the default Source.
+func Perm(n int) []int { return globalRand.Perm(n) }
+
+// Shuffle pseudo-randomizes the order of elements using the default Source.
+// n is the number of elements. Shuffle panics if n < 0.
+// swap swaps the elements with indexes i and j.
+func Shuffle(n int, swap func(i, j int)) { globalRand.Shuffle(n, swap) }
+
+// Read generates len(p) random bytes from the default Source and
+// writes them into p. It always returns len(p) and a nil error.
+// Read, unlike the Rand.Read method, is safe for concurrent use.
+func Read(p []byte) (n int, err error) { return globalRand.Read(p) }
+
+// NormFloat64 returns a normally distributed float64 in the range
+// [-math.MaxFloat64, +math.MaxFloat64] with
+// standard normal distribution (mean = 0, stddev = 1)
+// from the default Source.
+// To produce a different normal distribution, callers can
+// adjust the output using:
+//
+//  sample = NormFloat64() * desiredStdDev + desiredMean
+//
+func NormFloat64() float64 { return globalRand.NormFloat64() }
+
+// ExpFloat64 returns an exponentially distributed float64 in the range
+// (0, +math.MaxFloat64] with an exponential distribution whose rate parameter
+// (lambda) is 1 and whose mean is 1/lambda (1) from the default Source.
+// To produce a distribution with a different rate parameter,
+// callers can adjust the output using:
+//
+//  sample = ExpFloat64() / desiredRateParameter
+//
+func ExpFloat64() float64 { return globalRand.ExpFloat64() }
+
+type lockedSource struct {
+	lk  sync.Mutex
+	src *rngSource
+}
+
+func (r *lockedSource) Int63() (n int64) {
+	r.lk.Lock()
+	n = r.src.Int63()
+	r.lk.Unlock()
+	return
+}
+
+func (r *lockedSource) Uint64() (n uint64) {
+	r.lk.Lock()
+	n = r.src.Uint64()
+	r.lk.Unlock()
+	return
+}
+
+func (r *lockedSource) Seed(seed int64) {
+	r.lk.Lock()
+	r.src.Seed(seed)
+	r.lk.Unlock()
+}
+
+// seedPos implements Seed for a lockedSource without a race condition.
+func (r *lockedSource) seedPos(seed int64, readPos *int8) {
+	r.lk.Lock()
+	r.src.Seed(seed)
+	*readPos = 0
+	r.lk.Unlock()
+}
+
+// read implements Read for a lockedSource without a race condition.
+func (r *lockedSource) read(p []byte, readVal *int64, readPos *int8) (n int, err error) {
+	r.lk.Lock()
+	n, err = read(p, r.src, readVal, readPos)
+	r.lk.Unlock()
+	return
+}
diff --git a/contrib/go/_std_1.18/src/math/rand/rng.go b/contrib/go/_std_1.18/src/math/rand/rng.go
new file mode 100644
index 0000000000..f305df1a20
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/rand/rng.go
@@ -0,0 +1,252 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package rand
+
+/*
+ * Uniform distribution
+ *
+ * algorithm by
+ * DP Mitchell and JA Reeds
+ */
+
+const (
+	rngLen   = 607
+	rngTap   = 273
+	rngMax   = 1 << 63
+	rngMask  = rngMax - 1
+	int32max = (1 << 31) - 1
+)
+
+var (
+	// rngCooked used for seeding. See gen_cooked.go for details.
+	rngCooked [rngLen]int64 = [...]int64{
+		-4181792142133755926, -4576982950128230565, 1395769623340756751, 5333664234075297259,
+		-6347679516498800754, 9033628115061424579, 7143218595135194537, 4812947590706362721,
+		7937252194349799378, 5307299880338848416, 8209348851763925077, -7107630437535961764,
+		4593015457530856296, 8140875735541888011, -5903942795589686782, -603556388664454774,
+		-7496297993371156308, 113108499721038619, 4569519971459345583, -4160538177779461077,
+		-6835753265595711384, -6507240692498089696, 6559392774825876886, 7650093201692370310,
+		7684323884043752161, -8965504200858744418, -2629915517445760644, 271327514973697897,
+		-6433985589514657524, 1065192797246149621, 3344507881999356393, -4763574095074709175,
+		7465081662728599889, 1014950805555097187, -4773931307508785033, -5742262670416273165,
+		2418672789110888383, 5796562887576294778, 4484266064449540171, 3738982361971787048,
+		-4699774852342421385, 10530508058128498, -589538253572429690, -6598062107225984180,
+		8660405965245884302, 10162832508971942, -2682657355892958417, 7031802312784620857,
+		6240911277345944669, 831864355460801054, -1218937899312622917, 2116287251661052151,
+		2202309800992166967, 9161020366945053561, 4069299552407763864, 4936383537992622449,
+		457351505131524928, -8881176990926596454, -6375600354038175299, -7155351920868399290,
+		4368649989588021065, 887231587095185257, -3659780529968199312, -2407146836602825512,
+		5616972787034086048, -751562733459939242, 1686575021641186857, -5177887698780513806,
+		-4979215821652996885, -1375154703071198421, 5632136521049761902, -8390088894796940536,
+		-193645528485698615, -5979788902190688516, -4907000935050298721, -285522056888777828,
+		-2776431630044341707, 1679342092332374735, 6050638460742422078, -2229851317345194226,
+		-1582494184340482199, 5881353426285907985, 812786550756860885, 4541845584483343330,
+		-6497901820577766722, 4980675660146853729, -4012602956251539747, -329088717864244987,
+		-2896929232104691526, 1495812843684243920, -2153620458055647789, 7370257291860230865,
+		-2466442761497833547, 4706794511633873654, -1398851569026877145, 8549875090542453214,
+		-9189721207376179652, -7894453601103453165, 7297902601803624459, 1011190183918857495,
+		-6985347000036920864, 5147159997473910359, -8326859945294252826, 2659470849286379941,
+		6097729358393448602, -7491646050550022124, -5117116194870963097, -896216826133240300,
+		-745860416168701406, 5803876044675762232, -787954255994554146, -3234519180203704564,
+		-4507534739750823898, -1657200065590290694, 505808562678895611, -4153273856159712438,
+		-8381261370078904295, 572156825025677802, 1791881013492340891, 3393267094866038768,
+		-5444650186382539299, 2352769483186201278, -7930912453007408350, -325464993179687389,
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+		5907508150730407386, -8438615781380831356, 972392927514829904, -3801314342046600696,
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+		6657089965014657519, 5220884358887979358, 1796677326474620641, 5340761970648932916,
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+		-2601445448341207749, -7850010900052094367, 6527366231383600011, 3507654575162700890,
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+		-5321504681635821435, 7046310742295574065, -2376176645520785576, -7650733936335907755,
+		8850422670118399721, 3631909142291992901, 5158881091950831288, -6340413719511654215,
+		4763258931815816403, 6280052734341785344, -4979582628649810958, 2043464728020827976,
+		-2678071570832690343, 4562580375758598164, 5495451168795427352, -7485059175264624713,
+		553004618757816492, 6895160632757959823, -989748114590090637, 7139506338801360852,
+		-672480814466784139, 5535668688139305547, 2430933853350256242, -3821430778991574732,
+		-1063731997747047009, -3065878205254005442, 7632066283658143750, 6308328381617103346,
+		3681878764086140361, 3289686137190109749, 6587997200611086848, 244714774258135476,
+		-5143583659437639708, 8090302575944624335, 2945117363431356361, -8359047641006034763,
+		3009039260312620700, -793344576772241777, 401084700045993341, -1968749590416080887,
+		4707864159563588614, -3583123505891281857, -3240864324164777915, -5908273794572565703,
+		-3719524458082857382, -5281400669679581926, 8118566580304798074, 3839261274019871296,
+		7062410411742090847, -8481991033874568140, 6027994129690250817, -6725542042704711878,
+		-2971981702428546974, -7854441788951256975, 8809096399316380241, 6492004350391900708,
+		2462145737463489636, -8818543617934476634, -5070345602623085213, -8961586321599299868,
+		-3758656652254704451, -8630661632476012791, 6764129236657751224, -709716318315418359,
+		-3403028373052861600, -8838073512170985897, -3999237033416576341, -2920240395515973663,
+		-2073249475545404416, 368107899140673753, -6108185202296464250, -6307735683270494757,
+		4782583894627718279, 6718292300699989587, 8387085186914375220, 3387513132024756289,
+		4654329375432538231, -292704475491394206, -3848998599978456535, 7623042350483453954,
+		7725442901813263321, 9186225467561587250, -5132344747257272453, -6865740430362196008,
+		2530936820058611833, 1636551876240043639, -3658707362519810009, 1452244145334316253,
+		-7161729655835084979, -7943791770359481772, 9108481583171221009, -3200093350120725999,
+		5007630032676973346, 2153168792952589781, 6720334534964750538, -3181825545719981703,
+		3433922409283786309, 2285479922797300912, 3110614940896576130, -2856812446131932915,
+		-3804580617188639299, 7163298419643543757, 4891138053923696990, 580618510277907015,
+		1684034065251686769, 4429514767357295841, -8893025458299325803, -8103734041042601133,
+		7177515271653460134, 4589042248470800257, -1530083407795771245, 143607045258444228,
+		246994305896273627, -8356954712051676521, 6473547110565816071, 3092379936208876896,
+		2058427839513754051, -4089587328327907870, 8785882556301281247, -3074039370013608197,
+		-637529855400303673, 6137678347805511274, -7152924852417805802, 5708223427705576541,
+		-3223714144396531304, 4358391411789012426, 325123008708389849, 6837621693887290924,
+		4843721905315627004, -3212720814705499393, -3825019837890901156, 4602025990114250980,
+		1044646352569048800, 9106614159853161675, -8394115921626182539, -4304087667751778808,
+		2681532557646850893, 3681559472488511871, -3915372517896561773, -2889241648411946534,
+		-6564663803938238204, -8060058171802589521, 581945337509520675, 3648778920718647903,
+		-4799698790548231394, -7602572252857820065, 220828013409515943, -1072987336855386047,
+		4287360518296753003, -4633371852008891965, 5513660857261085186, -2258542936462001533,
+		-8744380348503999773, 8746140185685648781, 228500091334420247, 1356187007457302238,
+		3019253992034194581, 3152601605678500003, -8793219284148773595, 5559581553696971176,
+		4916432985369275664, -8559797105120221417, -5802598197927043732, 2868348622579915573,
+		-7224052902810357288, -5894682518218493085, 2587672709781371173, -7706116723325376475,
+		3092343956317362483, -5561119517847711700, 972445599196498113, -1558506600978816441,
+		1708913533482282562, -2305554874185907314, -6005743014309462908, -6653329009633068701,
+		-483583197311151195, 2488075924621352812, -4529369641467339140, -4663743555056261452,
+		2997203966153298104, 1282559373026354493, 240113143146674385, 8665713329246516443,
+		628141331766346752, -4651421219668005332, -7750560848702540400, 7596648026010355826,
+		-3132152619100351065, 7834161864828164065, 7103445518877254909, 4390861237357459201,
+		-4780718172614204074, -319889632007444440, 622261699494173647, -3186110786557562560,
+		-8718967088789066690, -1948156510637662747, -8212195255998774408, -7028621931231314745,
+		2623071828615234808, -4066058308780939700, -5484966924888173764, -6683604512778046238,
+		-6756087640505506466, 5256026990536851868, 7841086888628396109, 6640857538655893162,
+		-8021284697816458310, -7109857044414059830, -1689021141511844405, -4298087301956291063,
+		-4077748265377282003, -998231156719803476, 2719520354384050532, 9132346697815513771,
+		4332154495710163773, -2085582442760428892, 6994721091344268833, -2556143461985726874,
+		-8567931991128098309, 59934747298466858, -3098398008776739403, -265597256199410390,
+		2332206071942466437, -7522315324568406181, 3154897383618636503, -7585605855467168281,
+		-6762850759087199275, 197309393502684135, -8579694182469508493, 2543179307861934850,
+		4350769010207485119, -4468719947444108136, -7207776534213261296, -1224312577878317200,
+		4287946071480840813, 8362686366770308971, 6486469209321732151, -5605644191012979782,
+		-1669018511020473564, 4450022655153542367, -7618176296641240059, -3896357471549267421,
+		-4596796223304447488, -6531150016257070659, -8982326463137525940, -4125325062227681798,
+		-1306489741394045544, -8338554946557245229, 5329160409530630596, 7790979528857726136,
+		4955070238059373407, -4304834761432101506, -6215295852904371179, 3007769226071157901,
+		-6753025801236972788, 8928702772696731736, 7856187920214445904, -4748497451462800923,
+		7900176660600710914, -7082800908938549136, -6797926979589575837, -6737316883512927978,
+		4186670094382025798, 1883939007446035042, -414705992779907823, 3734134241178479257,
+		4065968871360089196, 6953124200385847784, -7917685222115876751, -7585632937840318161,
+		-5567246375906782599, -5256612402221608788, 3106378204088556331, -2894472214076325998,
+		4565385105440252958, 1979884289539493806, -6891578849933910383, 3783206694208922581,
+		8464961209802336085, 2843963751609577687, 3030678195484896323, -4429654462759003204,
+		4459239494808162889, 402587895800087237, 8057891408711167515, 4541888170938985079,
+		1042662272908816815, -3666068979732206850, 2647678726283249984, 2144477441549833761,
+		-3417019821499388721, -2105601033380872185, 5916597177708541638, -8760774321402454447,
+		8833658097025758785, 5970273481425315300, 563813119381731307, -6455022486202078793,
+		1598828206250873866, -4016978389451217698, -2988328551145513985, -6071154634840136312,
+		8469693267274066490, 125672920241807416, -3912292412830714870, -2559617104544284221,
+		-486523741806024092, -4735332261862713930, 5923302823487327109, -9082480245771672572,
+		-1808429243461201518, 7990420780896957397, 4317817392807076702, 3625184369705367340,
+		-6482649271566653105, -3480272027152017464, -3225473396345736649, -368878695502291645,
+		-3981164001421868007, -8522033136963788610, 7609280429197514109, 3020985755112334161,
+		-2572049329799262942, 2635195723621160615, 5144520864246028816, -8188285521126945980,
+		1567242097116389047, 8172389260191636581, -2885551685425483535, -7060359469858316883,
+		-6480181133964513127, -7317004403633452381, 6011544915663598137, 5932255307352610768,
+		2241128460406315459, -8327867140638080220, 3094483003111372717, 4583857460292963101,
+		9079887171656594975, -384082854924064405, -3460631649611717935, 4225072055348026230,
+		-7385151438465742745, 3801620336801580414, -399845416774701952, -7446754431269675473,
+		7899055018877642622, 5421679761463003041, 5521102963086275121, -4975092593295409910,
+		8735487530905098534, -7462844945281082830, -2080886987197029914, -1000715163927557685,
+		-4253840471931071485, -5828896094657903328, 6424174453260338141, 359248545074932887,
+		-5949720754023045210, -2426265837057637212, 3030918217665093212, -9077771202237461772,
+		-3186796180789149575, 740416251634527158, -2142944401404840226, 6951781370868335478,
+		399922722363687927, -8928469722407522623, -1378421100515597285, -8343051178220066766,
+		-3030716356046100229, -8811767350470065420, 9026808440365124461, 6440783557497587732,
+		4615674634722404292, 539897290441580544, 2096238225866883852, 8751955639408182687,
+		-7316147128802486205, 7381039757301768559, 6157238513393239656, -1473377804940618233,
+		8629571604380892756, 5280433031239081479, 7101611890139813254, 2479018537985767835,
+		7169176924412769570, -1281305539061572506, -7865612307799218120, 2278447439451174845,
+		3625338785743880657, 6477479539006708521, 8976185375579272206, -3712000482142939688,
+		1326024180520890843, 7537449876596048829, 5464680203499696154, 3189671183162196045,
+		6346751753565857109, -8982212049534145501, -6127578587196093755, -245039190118465649,
+		-6320577374581628592, 7208698530190629697, 7276901792339343736, -7490986807540332668,
+		4133292154170828382, 2918308698224194548, -7703910638917631350, -3929437324238184044,
+		-4300543082831323144, -6344160503358350167, 5896236396443472108, -758328221503023383,
+		-1894351639983151068, -307900319840287220, -6278469401177312761, -2171292963361310674,
+		8382142935188824023, 9103922860780351547, 4152330101494654406,
+	}
+)
+
+type rngSource struct {
+	tap  int           // index into vec
+	feed int           // index into vec
+	vec  [rngLen]int64 // current feedback register
+}
+
+// seed rng x[n+1] = 48271 * x[n] mod (2**31 - 1)
+func seedrand(x int32) int32 {
+	const (
+		A = 48271
+		Q = 44488
+		R = 3399
+	)
+
+	hi := x / Q
+	lo := x % Q
+	x = A*lo - R*hi
+	if x < 0 {
+		x += int32max
+	}
+	return x
+}
+
+// Seed uses the provided seed value to initialize the generator to a deterministic state.
+func (rng *rngSource) Seed(seed int64) {
+	rng.tap = 0
+	rng.feed = rngLen - rngTap
+
+	seed = seed % int32max
+	if seed < 0 {
+		seed += int32max
+	}
+	if seed == 0 {
+		seed = 89482311
+	}
+
+	x := int32(seed)
+	for i := -20; i < rngLen; i++ {
+		x = seedrand(x)
+		if i >= 0 {
+			var u int64
+			u = int64(x) << 40
+			x = seedrand(x)
+			u ^= int64(x) << 20
+			x = seedrand(x)
+			u ^= int64(x)
+			u ^= rngCooked[i]
+			rng.vec[i] = u
+		}
+	}
+}
+
+// Int63 returns a non-negative pseudo-random 63-bit integer as an int64.
+func (rng *rngSource) Int63() int64 {
+	return int64(rng.Uint64() & rngMask)
+}
+
+// Uint64 returns a non-negative pseudo-random 64-bit integer as an uint64.
+func (rng *rngSource) Uint64() uint64 {
+	rng.tap--
+	if rng.tap < 0 {
+		rng.tap += rngLen
+	}
+
+	rng.feed--
+	if rng.feed < 0 {
+		rng.feed += rngLen
+	}
+
+	x := rng.vec[rng.feed] + rng.vec[rng.tap]
+	rng.vec[rng.feed] = x
+	return uint64(x)
+}
diff --git a/contrib/go/_std_1.18/src/math/rand/zipf.go b/contrib/go/_std_1.18/src/math/rand/zipf.go
new file mode 100644
index 0000000000..f04c814eb7
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/rand/zipf.go
@@ -0,0 +1,77 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// W.Hormann, G.Derflinger:
+// "Rejection-Inversion to Generate Variates
+// from Monotone Discrete Distributions"
+// http://eeyore.wu-wien.ac.at/papers/96-04-04.wh-der.ps.gz
+
+package rand
+
+import "math"
+
+// A Zipf generates Zipf distributed variates.
+type Zipf struct {
+	r            *Rand
+	imax         float64
+	v            float64
+	q            float64
+	s            float64
+	oneminusQ    float64
+	oneminusQinv float64
+	hxm          float64
+	hx0minusHxm  float64
+}
+
+func (z *Zipf) h(x float64) float64 {
+	return math.Exp(z.oneminusQ*math.Log(z.v+x)) * z.oneminusQinv
+}
+
+func (z *Zipf) hinv(x float64) float64 {
+	return math.Exp(z.oneminusQinv*math.Log(z.oneminusQ*x)) - z.v
+}
+
+// NewZipf returns a Zipf variate generator.
+// The generator generates values k ∈ [0, imax]
+// such that P(k) is proportional to (v + k) ** (-s).
+// Requirements: s > 1 and v >= 1.
+func NewZipf(r *Rand, s float64, v float64, imax uint64) *Zipf {
+	z := new(Zipf)
+	if s <= 1.0 || v < 1 {
+		return nil
+	}
+	z.r = r
+	z.imax = float64(imax)
+	z.v = v
+	z.q = s
+	z.oneminusQ = 1.0 - z.q
+	z.oneminusQinv = 1.0 / z.oneminusQ
+	z.hxm = z.h(z.imax + 0.5)
+	z.hx0minusHxm = z.h(0.5) - math.Exp(math.Log(z.v)*(-z.q)) - z.hxm
+	z.s = 1 - z.hinv(z.h(1.5)-math.Exp(-z.q*math.Log(z.v+1.0)))
+	return z
+}
+
+// Uint64 returns a value drawn from the Zipf distribution described
+// by the Zipf object.
+func (z *Zipf) Uint64() uint64 {
+	if z == nil {
+		panic("rand: nil Zipf")
+	}
+	k := 0.0
+
+	for {
+		r := z.r.Float64() // r on [0,1]
+		ur := z.hxm + r*z.hx0minusHxm
+		x := z.hinv(ur)
+		k = math.Floor(x + 0.5)
+		if k-x <= z.s {
+			break
+		}
+		if ur >= z.h(k+0.5)-math.Exp(-math.Log(k+z.v)*z.q) {
+			break
+		}
+	}
+	return uint64(k)
+}
diff --git a/contrib/go/_std_1.18/src/math/remainder.go b/contrib/go/_std_1.18/src/math/remainder.go
new file mode 100644
index 0000000000..bf8bfd5553
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/remainder.go
@@ -0,0 +1,94 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// The original C code and the comment below are from
+// FreeBSD's /usr/src/lib/msun/src/e_remainder.c and came
+// with this notice. The go code is a simplified version of
+// the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+// __ieee754_remainder(x,y)
+// Return :
+//      returns  x REM y  =  x - [x/y]*y  as if in infinite
+//      precision arithmetic, where [x/y] is the (infinite bit)
+//      integer nearest x/y (in half way cases, choose the even one).
+// Method :
+//      Based on Mod() returning  x - [x/y]chopped * y  exactly.
+
+// Remainder returns the IEEE 754 floating-point remainder of x/y.
+//
+// Special cases are:
+//	Remainder(±Inf, y) = NaN
+//	Remainder(NaN, y) = NaN
+//	Remainder(x, 0) = NaN
+//	Remainder(x, ±Inf) = x
+//	Remainder(x, NaN) = NaN
+func Remainder(x, y float64) float64 {
+	if haveArchRemainder {
+		return archRemainder(x, y)
+	}
+	return remainder(x, y)
+}
+
+func remainder(x, y float64) float64 {
+	const (
+		Tiny    = 4.45014771701440276618e-308 // 0x0020000000000000
+		HalfMax = MaxFloat64 / 2
+	)
+	// special cases
+	switch {
+	case IsNaN(x) || IsNaN(y) || IsInf(x, 0) || y == 0:
+		return NaN()
+	case IsInf(y, 0):
+		return x
+	}
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+	if y < 0 {
+		y = -y
+	}
+	if x == y {
+		if sign {
+			zero := 0.0
+			return -zero
+		}
+		return 0
+	}
+	if y <= HalfMax {
+		x = Mod(x, y+y) // now x < 2y
+	}
+	if y < Tiny {
+		if x+x > y {
+			x -= y
+			if x+x >= y {
+				x -= y
+			}
+		}
+	} else {
+		yHalf := 0.5 * y
+		if x > yHalf {
+			x -= y
+			if x >= yHalf {
+				x -= y
+			}
+		}
+	}
+	if sign {
+		x = -x
+	}
+	return x
+}
diff --git a/contrib/go/_std_1.18/src/math/signbit.go b/contrib/go/_std_1.18/src/math/signbit.go
new file mode 100644
index 0000000000..f6e61d660e
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/signbit.go
@@ -0,0 +1,10 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Signbit reports whether x is negative or negative zero.
+func Signbit(x float64) bool {
+	return Float64bits(x)&(1<<63) != 0
+}
diff --git a/contrib/go/_std_1.18/src/math/sin.go b/contrib/go/_std_1.18/src/math/sin.go
new file mode 100644
index 0000000000..d95bb548e8
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/sin.go
@@ -0,0 +1,242 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Floating-point sine and cosine.
+*/
+
+// The original C code, the long comment, and the constants
+// below were from http://netlib.sandia.gov/cephes/cmath/sin.c,
+// available from http://www.netlib.org/cephes/cmath.tgz.
+// The go code is a simplified version of the original C.
+//
+//      sin.c
+//
+//      Circular sine
+//
+// SYNOPSIS:
+//
+// double x, y, sin();
+// y = sin( x );
+//
+// DESCRIPTION:
+//
+// Range reduction is into intervals of pi/4.  The reduction error is nearly
+// eliminated by contriving an extended precision modular arithmetic.
+//
+// Two polynomial approximating functions are employed.
+// Between 0 and pi/4 the sine is approximated by
+//      x  +  x**3 P(x**2).
+// Between pi/4 and pi/2 the cosine is represented as
+//      1  -  x**2 Q(x**2).
+//
+// ACCURACY:
+//
+//                      Relative error:
+// arithmetic   domain      # trials      peak         rms
+//    DEC       0, 10       150000       3.0e-17     7.8e-18
+//    IEEE -1.07e9,+1.07e9  130000       2.1e-16     5.4e-17
+//
+// Partial loss of accuracy begins to occur at x = 2**30 = 1.074e9.  The loss
+// is not gradual, but jumps suddenly to about 1 part in 10e7.  Results may
+// be meaningless for x > 2**49 = 5.6e14.
+//
+//      cos.c
+//
+//      Circular cosine
+//
+// SYNOPSIS:
+//
+// double x, y, cos();
+// y = cos( x );
+//
+// DESCRIPTION:
+//
+// Range reduction is into intervals of pi/4.  The reduction error is nearly
+// eliminated by contriving an extended precision modular arithmetic.
+//
+// Two polynomial approximating functions are employed.
+// Between 0 and pi/4 the cosine is approximated by
+//      1  -  x**2 Q(x**2).
+// Between pi/4 and pi/2 the sine is represented as
+//      x  +  x**3 P(x**2).
+//
+// ACCURACY:
+//
+//                      Relative error:
+// arithmetic   domain      # trials      peak         rms
+//    IEEE -1.07e9,+1.07e9  130000       2.1e-16     5.4e-17
+//    DEC        0,+1.07e9   17000       3.0e-17     7.2e-18
+//
+// Cephes Math Library Release 2.8:  June, 2000
+// Copyright 1984, 1987, 1989, 1992, 2000 by Stephen L. Moshier
+//
+// The readme file at http://netlib.sandia.gov/cephes/ says:
+//    Some software in this archive may be from the book _Methods and
+// Programs for Mathematical Functions_ (Prentice-Hall or Simon & Schuster
+// International, 1989) or from the Cephes Mathematical Library, a
+// commercial product. In either event, it is copyrighted by the author.
+// What you see here may be used freely but it comes with no support or
+// guarantee.
+//
+//   The two known misprints in the book are repaired here in the
+// source listings for the gamma function and the incomplete beta
+// integral.
+//
+//   Stephen L. Moshier
+//   moshier@na-net.ornl.gov
+
+// sin coefficients
+var _sin = [...]float64{
+	1.58962301576546568060e-10, // 0x3de5d8fd1fd19ccd
+	-2.50507477628578072866e-8, // 0xbe5ae5e5a9291f5d
+	2.75573136213857245213e-6,  // 0x3ec71de3567d48a1
+	-1.98412698295895385996e-4, // 0xbf2a01a019bfdf03
+	8.33333333332211858878e-3,  // 0x3f8111111110f7d0
+	-1.66666666666666307295e-1, // 0xbfc5555555555548
+}
+
+// cos coefficients
+var _cos = [...]float64{
+	-1.13585365213876817300e-11, // 0xbda8fa49a0861a9b
+	2.08757008419747316778e-9,   // 0x3e21ee9d7b4e3f05
+	-2.75573141792967388112e-7,  // 0xbe927e4f7eac4bc6
+	2.48015872888517045348e-5,   // 0x3efa01a019c844f5
+	-1.38888888888730564116e-3,  // 0xbf56c16c16c14f91
+	4.16666666666665929218e-2,   // 0x3fa555555555554b
+}
+
+// Cos returns the cosine of the radian argument x.
+//
+// Special cases are:
+//	Cos(±Inf) = NaN
+//	Cos(NaN) = NaN
+func Cos(x float64) float64 {
+	if haveArchCos {
+		return archCos(x)
+	}
+	return cos(x)
+}
+
+func cos(x float64) float64 {
+	const (
+		PI4A = 7.85398125648498535156e-1  // 0x3fe921fb40000000, Pi/4 split into three parts
+		PI4B = 3.77489470793079817668e-8  // 0x3e64442d00000000,
+		PI4C = 2.69515142907905952645e-15 // 0x3ce8469898cc5170,
+	)
+	// special cases
+	switch {
+	case IsNaN(x) || IsInf(x, 0):
+		return NaN()
+	}
+
+	// make argument positive
+	sign := false
+	x = Abs(x)
+
+	var j uint64
+	var y, z float64
+	if x >= reduceThreshold {
+		j, z = trigReduce(x)
+	} else {
+		j = uint64(x * (4 / Pi)) // integer part of x/(Pi/4), as integer for tests on the phase angle
+		y = float64(j)           // integer part of x/(Pi/4), as float
+
+		// map zeros to origin
+		if j&1 == 1 {
+			j++
+			y++
+		}
+		j &= 7                               // octant modulo 2Pi radians (360 degrees)
+		z = ((x - y*PI4A) - y*PI4B) - y*PI4C // Extended precision modular arithmetic
+	}
+
+	if j > 3 {
+		j -= 4
+		sign = !sign
+	}
+	if j > 1 {
+		sign = !sign
+	}
+
+	zz := z * z
+	if j == 1 || j == 2 {
+		y = z + z*zz*((((((_sin[0]*zz)+_sin[1])*zz+_sin[2])*zz+_sin[3])*zz+_sin[4])*zz+_sin[5])
+	} else {
+		y = 1.0 - 0.5*zz + zz*zz*((((((_cos[0]*zz)+_cos[1])*zz+_cos[2])*zz+_cos[3])*zz+_cos[4])*zz+_cos[5])
+	}
+	if sign {
+		y = -y
+	}
+	return y
+}
+
+// Sin returns the sine of the radian argument x.
+//
+// Special cases are:
+//	Sin(±0) = ±0
+//	Sin(±Inf) = NaN
+//	Sin(NaN) = NaN
+func Sin(x float64) float64 {
+	if haveArchSin {
+		return archSin(x)
+	}
+	return sin(x)
+}
+
+func sin(x float64) float64 {
+	const (
+		PI4A = 7.85398125648498535156e-1  // 0x3fe921fb40000000, Pi/4 split into three parts
+		PI4B = 3.77489470793079817668e-8  // 0x3e64442d00000000,
+		PI4C = 2.69515142907905952645e-15 // 0x3ce8469898cc5170,
+	)
+	// special cases
+	switch {
+	case x == 0 || IsNaN(x):
+		return x // return ±0 || NaN()
+	case IsInf(x, 0):
+		return NaN()
+	}
+
+	// make argument positive but save the sign
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+
+	var j uint64
+	var y, z float64
+	if x >= reduceThreshold {
+		j, z = trigReduce(x)
+	} else {
+		j = uint64(x * (4 / Pi)) // integer part of x/(Pi/4), as integer for tests on the phase angle
+		y = float64(j)           // integer part of x/(Pi/4), as float
+
+		// map zeros to origin
+		if j&1 == 1 {
+			j++
+			y++
+		}
+		j &= 7                               // octant modulo 2Pi radians (360 degrees)
+		z = ((x - y*PI4A) - y*PI4B) - y*PI4C // Extended precision modular arithmetic
+	}
+	// reflect in x axis
+	if j > 3 {
+		sign = !sign
+		j -= 4
+	}
+	zz := z * z
+	if j == 1 || j == 2 {
+		y = 1.0 - 0.5*zz + zz*zz*((((((_cos[0]*zz)+_cos[1])*zz+_cos[2])*zz+_cos[3])*zz+_cos[4])*zz+_cos[5])
+	} else {
+		y = z + z*zz*((((((_sin[0]*zz)+_sin[1])*zz+_sin[2])*zz+_sin[3])*zz+_sin[4])*zz+_sin[5])
+	}
+	if sign {
+		y = -y
+	}
+	return y
+}
diff --git a/contrib/go/_std_1.18/src/math/sincos.go b/contrib/go/_std_1.18/src/math/sincos.go
new file mode 100644
index 0000000000..5c5726f689
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/sincos.go
@@ -0,0 +1,72 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Coefficients _sin[] and _cos[] are found in pkg/math/sin.go.
+
+// Sincos returns Sin(x), Cos(x).
+//
+// Special cases are:
+//	Sincos(±0) = ±0, 1
+//	Sincos(±Inf) = NaN, NaN
+//	Sincos(NaN) = NaN, NaN
+func Sincos(x float64) (sin, cos float64) {
+	const (
+		PI4A = 7.85398125648498535156e-1  // 0x3fe921fb40000000, Pi/4 split into three parts
+		PI4B = 3.77489470793079817668e-8  // 0x3e64442d00000000,
+		PI4C = 2.69515142907905952645e-15 // 0x3ce8469898cc5170,
+	)
+	// special cases
+	switch {
+	case x == 0:
+		return x, 1 // return ±0.0, 1.0
+	case IsNaN(x) || IsInf(x, 0):
+		return NaN(), NaN()
+	}
+
+	// make argument positive
+	sinSign, cosSign := false, false
+	if x < 0 {
+		x = -x
+		sinSign = true
+	}
+
+	var j uint64
+	var y, z float64
+	if x >= reduceThreshold {
+		j, z = trigReduce(x)
+	} else {
+		j = uint64(x * (4 / Pi)) // integer part of x/(Pi/4), as integer for tests on the phase angle
+		y = float64(j)           // integer part of x/(Pi/4), as float
+
+		if j&1 == 1 { // map zeros to origin
+			j++
+			y++
+		}
+		j &= 7                               // octant modulo 2Pi radians (360 degrees)
+		z = ((x - y*PI4A) - y*PI4B) - y*PI4C // Extended precision modular arithmetic
+	}
+	if j > 3 { // reflect in x axis
+		j -= 4
+		sinSign, cosSign = !sinSign, !cosSign
+	}
+	if j > 1 {
+		cosSign = !cosSign
+	}
+
+	zz := z * z
+	cos = 1.0 - 0.5*zz + zz*zz*((((((_cos[0]*zz)+_cos[1])*zz+_cos[2])*zz+_cos[3])*zz+_cos[4])*zz+_cos[5])
+	sin = z + z*zz*((((((_sin[0]*zz)+_sin[1])*zz+_sin[2])*zz+_sin[3])*zz+_sin[4])*zz+_sin[5])
+	if j == 1 || j == 2 {
+		sin, cos = cos, sin
+	}
+	if cosSign {
+		cos = -cos
+	}
+	if sinSign {
+		sin = -sin
+	}
+	return
+}
diff --git a/contrib/go/_std_1.18/src/math/sinh.go b/contrib/go/_std_1.18/src/math/sinh.go
new file mode 100644
index 0000000000..9fe9b4e17a
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/sinh.go
@@ -0,0 +1,91 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Floating-point hyperbolic sine and cosine.
+
+	The exponential func is called for arguments
+	greater in magnitude than 0.5.
+
+	A series is used for arguments smaller in magnitude than 0.5.
+
+	Cosh(x) is computed from the exponential func for
+	all arguments.
+*/
+
+// Sinh returns the hyperbolic sine of x.
+//
+// Special cases are:
+//	Sinh(±0) = ±0
+//	Sinh(±Inf) = ±Inf
+//	Sinh(NaN) = NaN
+func Sinh(x float64) float64 {
+	if haveArchSinh {
+		return archSinh(x)
+	}
+	return sinh(x)
+}
+
+func sinh(x float64) float64 {
+	// The coefficients are #2029 from Hart & Cheney. (20.36D)
+	const (
+		P0 = -0.6307673640497716991184787251e+6
+		P1 = -0.8991272022039509355398013511e+5
+		P2 = -0.2894211355989563807284660366e+4
+		P3 = -0.2630563213397497062819489e+2
+		Q0 = -0.6307673640497716991212077277e+6
+		Q1 = 0.1521517378790019070696485176e+5
+		Q2 = -0.173678953558233699533450911e+3
+	)
+
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+
+	var temp float64
+	switch {
+	case x > 21:
+		temp = Exp(x) * 0.5
+
+	case x > 0.5:
+		ex := Exp(x)
+		temp = (ex - 1/ex) * 0.5
+
+	default:
+		sq := x * x
+		temp = (((P3*sq+P2)*sq+P1)*sq + P0) * x
+		temp = temp / (((sq+Q2)*sq+Q1)*sq + Q0)
+	}
+
+	if sign {
+		temp = -temp
+	}
+	return temp
+}
+
+// Cosh returns the hyperbolic cosine of x.
+//
+// Special cases are:
+//	Cosh(±0) = 1
+//	Cosh(±Inf) = +Inf
+//	Cosh(NaN) = NaN
+func Cosh(x float64) float64 {
+	if haveArchCosh {
+		return archCosh(x)
+	}
+	return cosh(x)
+}
+
+func cosh(x float64) float64 {
+	x = Abs(x)
+	if x > 21 {
+		return Exp(x) * 0.5
+	}
+	ex := Exp(x)
+	return (ex + 1/ex) * 0.5
+}
diff --git a/contrib/go/_std_1.18/src/math/sqrt.go b/contrib/go/_std_1.18/src/math/sqrt.go
new file mode 100644
index 0000000000..903d57d5e0
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/sqrt.go
@@ -0,0 +1,149 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// The original C code and the long comment below are
+// from FreeBSD's /usr/src/lib/msun/src/e_sqrt.c and
+// came with this notice. The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+// __ieee754_sqrt(x)
+// Return correctly rounded sqrt.
+//           -----------------------------------------
+//           | Use the hardware sqrt if you have one |
+//           -----------------------------------------
+// Method:
+//   Bit by bit method using integer arithmetic. (Slow, but portable)
+//   1. Normalization
+//      Scale x to y in [1,4) with even powers of 2:
+//      find an integer k such that  1 <= (y=x*2**(2k)) < 4, then
+//              sqrt(x) = 2**k * sqrt(y)
+//   2. Bit by bit computation
+//      Let q  = sqrt(y) truncated to i bit after binary point (q = 1),
+//           i                                                   0
+//                                     i+1         2
+//          s  = 2*q , and      y  =  2   * ( y - q  ).          (1)
+//           i      i            i                 i
+//
+//      To compute q    from q , one checks whether
+//                  i+1       i
+//
+//                            -(i+1) 2
+//                      (q + 2      )  <= y.                     (2)
+//                        i
+//                                                            -(i+1)
+//      If (2) is false, then q   = q ; otherwise q   = q  + 2      .
+//                             i+1   i             i+1   i
+//
+//      With some algebraic manipulation, it is not difficult to see
+//      that (2) is equivalent to
+//                             -(i+1)
+//                      s  +  2       <= y                       (3)
+//                       i                i
+//
+//      The advantage of (3) is that s  and y  can be computed by
+//                                    i      i
+//      the following recurrence formula:
+//          if (3) is false
+//
+//          s     =  s  ,       y    = y   ;                     (4)
+//           i+1      i          i+1    i
+//
+//      otherwise,
+//                         -i                      -(i+1)
+//          s     =  s  + 2  ,  y    = y  -  s  - 2              (5)
+//           i+1      i          i+1    i     i
+//
+//      One may easily use induction to prove (4) and (5).
+//      Note. Since the left hand side of (3) contain only i+2 bits,
+//            it is not necessary to do a full (53-bit) comparison
+//            in (3).
+//   3. Final rounding
+//      After generating the 53 bits result, we compute one more bit.
+//      Together with the remainder, we can decide whether the
+//      result is exact, bigger than 1/2ulp, or less than 1/2ulp
+//      (it will never equal to 1/2ulp).
+//      The rounding mode can be detected by checking whether
+//      huge + tiny is equal to huge, and whether huge - tiny is
+//      equal to huge for some floating point number "huge" and "tiny".
+//
+//
+// Notes:  Rounding mode detection omitted. The constants "mask", "shift",
+// and "bias" are found in src/math/bits.go
+
+// Sqrt returns the square root of x.
+//
+// Special cases are:
+//	Sqrt(+Inf) = +Inf
+//	Sqrt(±0) = ±0
+//	Sqrt(x < 0) = NaN
+//	Sqrt(NaN) = NaN
+func Sqrt(x float64) float64 {
+	if haveArchSqrt {
+		return archSqrt(x)
+	}
+	return sqrt(x)
+}
+
+// Note: Sqrt is implemented in assembly on some systems.
+// Others have assembly stubs that jump to func sqrt below.
+// On systems where Sqrt is a single instruction, the compiler
+// may turn a direct call into a direct use of that instruction instead.
+
+func sqrt(x float64) float64 {
+	// special cases
+	switch {
+	case x == 0 || IsNaN(x) || IsInf(x, 1):
+		return x
+	case x < 0:
+		return NaN()
+	}
+	ix := Float64bits(x)
+	// normalize x
+	exp := int((ix >> shift) & mask)
+	if exp == 0 { // subnormal x
+		for ix&(1<<shift) == 0 {
+			ix <<= 1
+			exp--
+		}
+		exp++
+	}
+	exp -= bias // unbias exponent
+	ix &^= mask << shift
+	ix |= 1 << shift
+	if exp&1 == 1 { // odd exp, double x to make it even
+		ix <<= 1
+	}
+	exp >>= 1 // exp = exp/2, exponent of square root
+	// generate sqrt(x) bit by bit
+	ix <<= 1
+	var q, s uint64               // q = sqrt(x)
+	r := uint64(1 << (shift + 1)) // r = moving bit from MSB to LSB
+	for r != 0 {
+		t := s + r
+		if t <= ix {
+			s = t + r
+			ix -= t
+			q += r
+		}
+		ix <<= 1
+		r >>= 1
+	}
+	// final rounding
+	if ix != 0 { // remainder, result not exact
+		q += q & 1 // round according to extra bit
+	}
+	ix = q>>1 + uint64(exp-1+bias)<<shift // significand + biased exponent
+	return Float64frombits(ix)
+}
diff --git a/contrib/go/_std_1.18/src/math/sqrt_amd64.s b/contrib/go/_std_1.18/src/math/sqrt_amd64.s
new file mode 100644
index 0000000000..c3b110e7c0
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/sqrt_amd64.s
@@ -0,0 +1,12 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "textflag.h"
+
+// func archSqrt(x float64) float64
+TEXT ·archSqrt(SB), NOSPLIT, $0
+	XORPS  X0, X0 // break dependency
+	SQRTSD x+0(FP), X0
+	MOVSD  X0, ret+8(FP)
+	RET
diff --git a/contrib/go/_std_1.18/src/math/sqrt_asm.go b/contrib/go/_std_1.18/src/math/sqrt_asm.go
new file mode 100644
index 0000000000..2cec1a5903
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/sqrt_asm.go
@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build 386 || amd64 || arm64 || arm || mips || mipsle || ppc64 || ppc64le || s390x || riscv64 || wasm
+
+package math
+
+const haveArchSqrt = true
+
+func archSqrt(x float64) float64
diff --git a/contrib/go/_std_1.18/src/math/stubs.go b/contrib/go/_std_1.18/src/math/stubs.go
new file mode 100644
index 0000000000..c4350d4b87
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/stubs.go
@@ -0,0 +1,160 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !s390x
+
+// This is a large group of functions that most architectures don't
+// implement in assembly.
+
+package math
+
+const haveArchAcos = false
+
+func archAcos(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchAcosh = false
+
+func archAcosh(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchAsin = false
+
+func archAsin(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchAsinh = false
+
+func archAsinh(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchAtan = false
+
+func archAtan(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchAtan2 = false
+
+func archAtan2(y, x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchAtanh = false
+
+func archAtanh(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchCbrt = false
+
+func archCbrt(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchCos = false
+
+func archCos(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchCosh = false
+
+func archCosh(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchErf = false
+
+func archErf(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchErfc = false
+
+func archErfc(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchExpm1 = false
+
+func archExpm1(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchFrexp = false
+
+func archFrexp(x float64) (float64, int) {
+	panic("not implemented")
+}
+
+const haveArchLdexp = false
+
+func archLdexp(frac float64, exp int) float64 {
+	panic("not implemented")
+}
+
+const haveArchLog10 = false
+
+func archLog10(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchLog2 = false
+
+func archLog2(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchLog1p = false
+
+func archLog1p(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchMod = false
+
+func archMod(x, y float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchPow = false
+
+func archPow(x, y float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchRemainder = false
+
+func archRemainder(x, y float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchSin = false
+
+func archSin(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchSinh = false
+
+func archSinh(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchTan = false
+
+func archTan(x float64) float64 {
+	panic("not implemented")
+}
+
+const haveArchTanh = false
+
+func archTanh(x float64) float64 {
+	panic("not implemented")
+}
diff --git a/contrib/go/_std_1.18/src/math/tan.go b/contrib/go/_std_1.18/src/math/tan.go
new file mode 100644
index 0000000000..a25417f527
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/tan.go
@@ -0,0 +1,139 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+/*
+	Floating-point tangent.
+*/
+
+// The original C code, the long comment, and the constants
+// below were from http://netlib.sandia.gov/cephes/cmath/sin.c,
+// available from http://www.netlib.org/cephes/cmath.tgz.
+// The go code is a simplified version of the original C.
+//
+//      tan.c
+//
+//      Circular tangent
+//
+// SYNOPSIS:
+//
+// double x, y, tan();
+// y = tan( x );
+//
+// DESCRIPTION:
+//
+// Returns the circular tangent of the radian argument x.
+//
+// Range reduction is modulo pi/4.  A rational function
+//       x + x**3 P(x**2)/Q(x**2)
+// is employed in the basic interval [0, pi/4].
+//
+// ACCURACY:
+//                      Relative error:
+// arithmetic   domain     # trials      peak         rms
+//    DEC      +-1.07e9      44000      4.1e-17     1.0e-17
+//    IEEE     +-1.07e9      30000      2.9e-16     8.1e-17
+//
+// Partial loss of accuracy begins to occur at x = 2**30 = 1.074e9.  The loss
+// is not gradual, but jumps suddenly to about 1 part in 10e7.  Results may
+// be meaningless for x > 2**49 = 5.6e14.
+// [Accuracy loss statement from sin.go comments.]
+//
+// Cephes Math Library Release 2.8:  June, 2000
+// Copyright 1984, 1987, 1989, 1992, 2000 by Stephen L. Moshier
+//
+// The readme file at http://netlib.sandia.gov/cephes/ says:
+//    Some software in this archive may be from the book _Methods and
+// Programs for Mathematical Functions_ (Prentice-Hall or Simon & Schuster
+// International, 1989) or from the Cephes Mathematical Library, a
+// commercial product. In either event, it is copyrighted by the author.
+// What you see here may be used freely but it comes with no support or
+// guarantee.
+//
+//   The two known misprints in the book are repaired here in the
+// source listings for the gamma function and the incomplete beta
+// integral.
+//
+//   Stephen L. Moshier
+//   moshier@na-net.ornl.gov
+
+// tan coefficients
+var _tanP = [...]float64{
+	-1.30936939181383777646e4, // 0xc0c992d8d24f3f38
+	1.15351664838587416140e6,  // 0x413199eca5fc9ddd
+	-1.79565251976484877988e7, // 0xc1711fead3299176
+}
+var _tanQ = [...]float64{
+	1.00000000000000000000e0,
+	1.36812963470692954678e4,  //0x40cab8a5eeb36572
+	-1.32089234440210967447e6, //0xc13427bc582abc96
+	2.50083801823357915839e7,  //0x4177d98fc2ead8ef
+	-5.38695755929454629881e7, //0xc189afe03cbe5a31
+}
+
+// Tan returns the tangent of the radian argument x.
+//
+// Special cases are:
+//	Tan(±0) = ±0
+//	Tan(±Inf) = NaN
+//	Tan(NaN) = NaN
+func Tan(x float64) float64 {
+	if haveArchTan {
+		return archTan(x)
+	}
+	return tan(x)
+}
+
+func tan(x float64) float64 {
+	const (
+		PI4A = 7.85398125648498535156e-1  // 0x3fe921fb40000000, Pi/4 split into three parts
+		PI4B = 3.77489470793079817668e-8  // 0x3e64442d00000000,
+		PI4C = 2.69515142907905952645e-15 // 0x3ce8469898cc5170,
+	)
+	// special cases
+	switch {
+	case x == 0 || IsNaN(x):
+		return x // return ±0 || NaN()
+	case IsInf(x, 0):
+		return NaN()
+	}
+
+	// make argument positive but save the sign
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+	var j uint64
+	var y, z float64
+	if x >= reduceThreshold {
+		j, z = trigReduce(x)
+	} else {
+		j = uint64(x * (4 / Pi)) // integer part of x/(Pi/4), as integer for tests on the phase angle
+		y = float64(j)           // integer part of x/(Pi/4), as float
+
+		/* map zeros and singularities to origin */
+		if j&1 == 1 {
+			j++
+			y++
+		}
+
+		z = ((x - y*PI4A) - y*PI4B) - y*PI4C
+	}
+	zz := z * z
+
+	if zz > 1e-14 {
+		y = z + z*(zz*(((_tanP[0]*zz)+_tanP[1])*zz+_tanP[2])/((((zz+_tanQ[1])*zz+_tanQ[2])*zz+_tanQ[3])*zz+_tanQ[4]))
+	} else {
+		y = z
+	}
+	if j&2 == 2 {
+		y = -1 / y
+	}
+	if sign {
+		y = -y
+	}
+	return y
+}
diff --git a/contrib/go/_std_1.18/src/math/tanh.go b/contrib/go/_std_1.18/src/math/tanh.go
new file mode 100644
index 0000000000..a825678424
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/tanh.go
@@ -0,0 +1,104 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// The original C code, the long comment, and the constants
+// below were from http://netlib.sandia.gov/cephes/cmath/sin.c,
+// available from http://www.netlib.org/cephes/cmath.tgz.
+// The go code is a simplified version of the original C.
+//      tanh.c
+//
+//      Hyperbolic tangent
+//
+// SYNOPSIS:
+//
+// double x, y, tanh();
+//
+// y = tanh( x );
+//
+// DESCRIPTION:
+//
+// Returns hyperbolic tangent of argument in the range MINLOG to MAXLOG.
+//      MAXLOG = 8.8029691931113054295988e+01 = log(2**127)
+//      MINLOG = -8.872283911167299960540e+01 = log(2**-128)
+//
+// A rational function is used for |x| < 0.625.  The form
+// x + x**3 P(x)/Q(x) of Cody & Waite is employed.
+// Otherwise,
+//      tanh(x) = sinh(x)/cosh(x) = 1  -  2/(exp(2x) + 1).
+//
+// ACCURACY:
+//
+//                      Relative error:
+// arithmetic   domain     # trials      peak         rms
+//    IEEE      -2,2        30000       2.5e-16     5.8e-17
+//
+// Cephes Math Library Release 2.8:  June, 2000
+// Copyright 1984, 1987, 1989, 1992, 2000 by Stephen L. Moshier
+//
+// The readme file at http://netlib.sandia.gov/cephes/ says:
+//    Some software in this archive may be from the book _Methods and
+// Programs for Mathematical Functions_ (Prentice-Hall or Simon & Schuster
+// International, 1989) or from the Cephes Mathematical Library, a
+// commercial product. In either event, it is copyrighted by the author.
+// What you see here may be used freely but it comes with no support or
+// guarantee.
+//
+//   The two known misprints in the book are repaired here in the
+// source listings for the gamma function and the incomplete beta
+// integral.
+//
+//   Stephen L. Moshier
+//   moshier@na-net.ornl.gov
+//
+
+var tanhP = [...]float64{
+	-9.64399179425052238628e-1,
+	-9.92877231001918586564e1,
+	-1.61468768441708447952e3,
+}
+var tanhQ = [...]float64{
+	1.12811678491632931402e2,
+	2.23548839060100448583e3,
+	4.84406305325125486048e3,
+}
+
+// Tanh returns the hyperbolic tangent of x.
+//
+// Special cases are:
+//	Tanh(±0) = ±0
+//	Tanh(±Inf) = ±1
+//	Tanh(NaN) = NaN
+func Tanh(x float64) float64 {
+	if haveArchTanh {
+		return archTanh(x)
+	}
+	return tanh(x)
+}
+
+func tanh(x float64) float64 {
+	const MAXLOG = 8.8029691931113054295988e+01 // log(2**127)
+	z := Abs(x)
+	switch {
+	case z > 0.5*MAXLOG:
+		if x < 0 {
+			return -1
+		}
+		return 1
+	case z >= 0.625:
+		s := Exp(2 * z)
+		z = 1 - 2/(s+1)
+		if x < 0 {
+			z = -z
+		}
+	default:
+		if x == 0 {
+			return x
+		}
+		s := x * x
+		z = x + x*s*((tanhP[0]*s+tanhP[1])*s+tanhP[2])/(((s+tanhQ[0])*s+tanhQ[1])*s+tanhQ[2])
+	}
+	return z
+}
diff --git a/contrib/go/_std_1.18/src/math/trig_reduce.go b/contrib/go/_std_1.18/src/math/trig_reduce.go
new file mode 100644
index 0000000000..5cdf4fa013
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/trig_reduce.go
@@ -0,0 +1,100 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+import (
+	"math/bits"
+)
+
+// reduceThreshold is the maximum value of x where the reduction using Pi/4
+// in 3 float64 parts still gives accurate results. This threshold
+// is set by y*C being representable as a float64 without error
+// where y is given by y = floor(x * (4 / Pi)) and C is the leading partial
+// terms of 4/Pi. Since the leading terms (PI4A and PI4B in sin.go) have 30
+// and 32 trailing zero bits, y should have less than 30 significant bits.
+//	y < 1<<30  -> floor(x*4/Pi) < 1<<30 -> x < (1<<30 - 1) * Pi/4
+// So, conservatively we can take x < 1<<29.
+// Above this threshold Payne-Hanek range reduction must be used.
+const reduceThreshold = 1 << 29
+
+// trigReduce implements Payne-Hanek range reduction by Pi/4
+// for x > 0. It returns the integer part mod 8 (j) and
+// the fractional part (z) of x / (Pi/4).
+// The implementation is based on:
+// "ARGUMENT REDUCTION FOR HUGE ARGUMENTS: Good to the Last Bit"
+// K. C. Ng et al, March 24, 1992
+// The simulated multi-precision calculation of x*B uses 64-bit integer arithmetic.
+func trigReduce(x float64) (j uint64, z float64) {
+	const PI4 = Pi / 4
+	if x < PI4 {
+		return 0, x
+	}
+	// Extract out the integer and exponent such that,
+	// x = ix * 2 ** exp.
+	ix := Float64bits(x)
+	exp := int(ix>>shift&mask) - bias - shift
+	ix &^= mask << shift
+	ix |= 1 << shift
+	// Use the exponent to extract the 3 appropriate uint64 digits from mPi4,
+	// B ~ (z0, z1, z2), such that the product leading digit has the exponent -61.
+	// Note, exp >= -53 since x >= PI4 and exp < 971 for maximum float64.
+	digit, bitshift := uint(exp+61)/64, uint(exp+61)%64
+	z0 := (mPi4[digit] << bitshift) | (mPi4[digit+1] >> (64 - bitshift))
+	z1 := (mPi4[digit+1] << bitshift) | (mPi4[digit+2] >> (64 - bitshift))
+	z2 := (mPi4[digit+2] << bitshift) | (mPi4[digit+3] >> (64 - bitshift))
+	// Multiply mantissa by the digits and extract the upper two digits (hi, lo).
+	z2hi, _ := bits.Mul64(z2, ix)
+	z1hi, z1lo := bits.Mul64(z1, ix)
+	z0lo := z0 * ix
+	lo, c := bits.Add64(z1lo, z2hi, 0)
+	hi, _ := bits.Add64(z0lo, z1hi, c)
+	// The top 3 bits are j.
+	j = hi >> 61
+	// Extract the fraction and find its magnitude.
+	hi = hi<<3 | lo>>61
+	lz := uint(bits.LeadingZeros64(hi))
+	e := uint64(bias - (lz + 1))
+	// Clear implicit mantissa bit and shift into place.
+	hi = (hi << (lz + 1)) | (lo >> (64 - (lz + 1)))
+	hi >>= 64 - shift
+	// Include the exponent and convert to a float.
+	hi |= e << shift
+	z = Float64frombits(hi)
+	// Map zeros to origin.
+	if j&1 == 1 {
+		j++
+		j &= 7
+		z--
+	}
+	// Multiply the fractional part by pi/4.
+	return j, z * PI4
+}
+
+// mPi4 is the binary digits of 4/pi as a uint64 array,
+// that is, 4/pi = Sum mPi4[i]*2^(-64*i)
+// 19 64-bit digits and the leading one bit give 1217 bits
+// of precision to handle the largest possible float64 exponent.
+var mPi4 = [...]uint64{
+	0x0000000000000001,
+	0x45f306dc9c882a53,
+	0xf84eafa3ea69bb81,
+	0xb6c52b3278872083,
+	0xfca2c757bd778ac3,
+	0x6e48dc74849ba5c0,
+	0x0c925dd413a32439,
+	0xfc3bd63962534e7d,
+	0xd1046bea5d768909,
+	0xd338e04d68befc82,
+	0x7323ac7306a673e9,
+	0x3908bf177bf25076,
+	0x3ff12fffbc0b301f,
+	0xde5e2316b414da3e,
+	0xda6cfd9e4f96136e,
+	0x9e8c7ecd3cbfd45a,
+	0xea4f758fd7cbe2f6,
+	0x7a0e73ef14a525d4,
+	0xd7f6bf623f1aba10,
+	0xac06608df8f6d757,
+}
diff --git a/contrib/go/_std_1.18/src/math/unsafe.go b/contrib/go/_std_1.18/src/math/unsafe.go
new file mode 100644
index 0000000000..e59f50ca62
--- /dev/null
+++ b/contrib/go/_std_1.18/src/math/unsafe.go
@@ -0,0 +1,29 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+import "unsafe"
+
+// Float32bits returns the IEEE 754 binary representation of f,
+// with the sign bit of f and the result in the same bit position.
+// Float32bits(Float32frombits(x)) == x.
+func Float32bits(f float32) uint32 { return *(*uint32)(unsafe.Pointer(&f)) }
+
+// Float32frombits returns the floating-point number corresponding
+// to the IEEE 754 binary representation b, with the sign bit of b
+// and the result in the same bit position.
+// Float32frombits(Float32bits(x)) == x.
+func Float32frombits(b uint32) float32 { return *(*float32)(unsafe.Pointer(&b)) }
+
+// Float64bits returns the IEEE 754 binary representation of f,
+// with the sign bit of f and the result in the same bit position,
+// and Float64bits(Float64frombits(x)) == x.
+func Float64bits(f float64) uint64 { return *(*uint64)(unsafe.Pointer(&f)) }
+
+// Float64frombits returns the floating-point number corresponding
+// to the IEEE 754 binary representation b, with the sign bit of b
+// and the result in the same bit position.
+// Float64frombits(Float64bits(x)) == x.
+func Float64frombits(b uint64) float64 { return *(*float64)(unsafe.Pointer(&b)) }