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// 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 runtime
import "unsafe"
const (
float64Mask = 0x7FF
float64Shift = 64 - 11 - 1
float64Bias = 1023
)
var inf = float64frombits(0x7FF0000000000000)
// 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.
return f != f
}
// isFinite reports whether f is neither NaN nor an infinity.
func isFinite(f float64) bool {
return !isNaN(f - f)
}
// isInf reports whether f is an infinity.
func isInf(f float64) bool {
return !isNaN(f) && !isFinite(f)
}
// abs returns the absolute value of x.
//
// Special cases are:
//
// abs(±Inf) = +Inf
// abs(NaN) = NaN
func abs(x float64) float64 {
const sign = 1 << 63
return float64frombits(float64bits(x) &^ sign)
}
// 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)
}
// float64bits returns the IEEE 754 binary representation of f.
func float64bits(f float64) uint64 {
return *(*uint64)(unsafe.Pointer(&f))
}
// float64frombits returns the floating point number corresponding
// the IEEE 754 binary representation b.
func float64frombits(b uint64) float64 {
return *(*float64)(unsafe.Pointer(&b))
}
// floor returns the greatest integer value less than or equal to x.
//
// Special cases are:
//
// floor(±0) = ±0
// floor(±Inf) = ±Inf
// floor(NaN) = NaN
//
// N.B. Portable floor copied from math. math also has optimized arch-specific
// implementations.
func floor(x float64) float64 {
if x == 0 || isNaN(x) || isInf(x) {
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
//
// N.B. Portable ceil copied from math. math also has optimized arch-specific
// implementations.
func ceil(x float64) float64 {
return -floor(-x)
}
// 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
//
// N.B. Portable modf copied from math. math also has optimized arch-specific
// implementations.
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>>float64Shift)&float64Mask - float64Bias
// 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
}
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