90 lines
2.2 KiB
C++
90 lines
2.2 KiB
C++
// (C) Copyright Matt Borland 2021.
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// Constepxr implementation of abs (see c.math.abs secion 26.8.2 of the ISO standard)
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#ifndef BOOST_MATH_CCMATH_ABS
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#define BOOST_MATH_CCMATH_ABS
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#include <boost/math/ccmath/detail/config.hpp>
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#ifdef BOOST_MATH_NO_CCMATH
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#error "The header <boost/math/abs.hpp> can only be used in C++17 and later."
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#endif
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#include <boost/math/tools/assert.hpp>
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#include <boost/math/ccmath/isnan.hpp>
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#include <boost/math/ccmath/isinf.hpp>
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namespace boost::math::ccmath {
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namespace detail {
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template <typename T>
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constexpr T abs_impl(T x) noexcept
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{
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if ((boost::math::ccmath::isnan)(x))
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{
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return std::numeric_limits<T>::quiet_NaN();
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}
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else if (x == static_cast<T>(-0))
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{
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return static_cast<T>(0);
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}
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if constexpr (std::is_integral_v<T>)
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{
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BOOST_MATH_ASSERT(x != (std::numeric_limits<T>::min)());
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}
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return x >= 0 ? x : -x;
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}
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} // Namespace detail
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template <typename T, std::enable_if_t<!std::is_unsigned_v<T>, bool> = true>
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constexpr T abs(T x) noexcept
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{
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if(BOOST_MATH_IS_CONSTANT_EVALUATED(x))
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{
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return detail::abs_impl<T>(x);
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}
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else
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{
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using std::abs;
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return abs(x);
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}
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}
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// If abs() is called with an argument of type X for which is_unsigned_v<X> is true and if X
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// cannot be converted to int by integral promotion (7.3.7), the program is ill-formed.
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template <typename T, std::enable_if_t<std::is_unsigned_v<T>, bool> = true>
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constexpr T abs(T x) noexcept
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{
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if constexpr (std::is_convertible_v<T, int>)
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{
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return detail::abs_impl<int>(static_cast<int>(x));
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}
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else
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{
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static_assert(sizeof(T) == 0, "Taking the absolute value of an unsigned value not convertible to int is UB.");
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return T(0); // Unreachable, but suppresses warnings
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}
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}
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constexpr long int labs(long int j) noexcept
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{
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return boost::math::ccmath::abs(j);
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}
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constexpr long long int llabs(long long int j) noexcept
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{
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return boost::math::ccmath::abs(j);
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}
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} // Namespaces
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#endif // BOOST_MATH_CCMATH_ABS
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