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// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___NUMERIC_MIDPOINT_H
#define _LIBCPP___NUMERIC_MIDPOINT_H
#include <__config>
#include <limits>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER > 17
template <class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<is_integral_v<_Tp> && !is_same_v<bool, _Tp> && !is_null_pointer_v<_Tp>, _Tp>
midpoint(_Tp __a, _Tp __b) noexcept
_LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
{
using _Up = make_unsigned_t<_Tp>;
constexpr _Up __bitshift = numeric_limits<_Up>::digits - 1;
_Up __diff = _Up(__b) - _Up(__a);
_Up __sign_bit = __b < __a;
_Up __half_diff = (__diff / 2) + (__sign_bit << __bitshift) + (__sign_bit & __diff);
return __a + __half_diff;
}
template <class _TPtr>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<is_pointer_v<_TPtr>
&& is_object_v<remove_pointer_t<_TPtr>>
&& ! is_void_v<remove_pointer_t<_TPtr>>
&& (sizeof(remove_pointer_t<_TPtr>) > 0), _TPtr>
midpoint(_TPtr __a, _TPtr __b) noexcept
{
return __a + _VSTD::midpoint(ptrdiff_t(0), __b - __a);
}
template <typename _Tp>
constexpr int __sign(_Tp __val) {
return (_Tp(0) < __val) - (__val < _Tp(0));
}
template <typename _Fp>
constexpr _Fp __fp_abs(_Fp __f) { return __f >= 0 ? __f : -__f; }
template <class _Fp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<is_floating_point_v<_Fp>, _Fp>
midpoint(_Fp __a, _Fp __b) noexcept
{
constexpr _Fp __lo = numeric_limits<_Fp>::min()*2;
constexpr _Fp __hi = numeric_limits<_Fp>::max()/2;
return __fp_abs(__a) <= __hi && __fp_abs(__b) <= __hi ? // typical case: overflow is impossible
(__a + __b)/2 : // always correctly rounded
__fp_abs(__a) < __lo ? __a + __b/2 : // not safe to halve a
__fp_abs(__b) < __lo ? __a/2 + __b : // not safe to halve b
__a/2 + __b/2; // otherwise correctly rounded
}
#endif // _LIBCPP_STD_VER > 17
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___NUMERIC_MIDPOINT_H
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