63e88f80
 Hu Chunming
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// (C) Copyright Matt Borland 2021.
// Use, modification and distribution are subject to the
// Boost Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// Constepxr implementation of abs (see c.math.abs secion 26.8.2 of the ISO standard)
#ifndef BOOST_MATH_CCMATH_ABS
#define BOOST_MATH_CCMATH_ABS
#include <cmath>
#include <type_traits>
#include <limits>
#include <boost/math/tools/is_constant_evaluated.hpp>
#include <boost/math/tools/assert.hpp>
#include <boost/math/ccmath/isnan.hpp>
#include <boost/math/ccmath/isinf.hpp>
namespace boost::math::ccmath {
namespace detail {
template <typename T>
constexpr T abs_impl(T x) noexcept
{
if (boost::math::ccmath::isnan(x))
{
return std::numeric_limits<T>::quiet_NaN();
}
else if (x == static_cast<T>(-0))
{
return static_cast<T>(0);
}
if constexpr (std::is_integral_v<T>)
{
BOOST_MATH_ASSERT(x != (std::numeric_limits<T>::min)());
}
return x >= 0 ? x : -x;
}
} // Namespace detail
template <typename T, std::enable_if_t<!std::is_unsigned_v<T>, bool> = true>
constexpr T abs(T x) noexcept
{
if(BOOST_MATH_IS_CONSTANT_EVALUATED(x))
{
return detail::abs_impl<T>(x);
}
else
{
using std::abs;
return abs(x);
}
}
// If abs() is called with an argument of type X for which is_unsigned_v<X> is true and if X
// cannot be converted to int by integral promotion (7.3.7), the program is ill-formed.
template <typename T, std::enable_if_t<std::is_unsigned_v<T>, bool> = true>
constexpr T abs(T x) noexcept
{
if constexpr (std::is_convertible_v<T, int>)
{
return detail::abs_impl<int>(static_cast<int>(x));
}
else
{
static_assert(sizeof(T) == 0, "Taking the absolute value of an unsigned value not covertible to int is UB.");
return T(0); // Unreachable, but suppresses warnings
}
}
constexpr long int labs(long int j) noexcept
{
return boost::math::ccmath::abs(j);
}
constexpr long long int llabs(long long int j) noexcept
{
return boost::math::ccmath::abs(j);
}
} // Namespaces
#endif // BOOST_MATH_CCMATH_ABS
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