copysign.hpp

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/*=============================================================================
  Copyright (c) 2011-2016 Bolero MURAKAMI
  https://github.com/bolero-MURAKAMI/Sprout
  Copyright (C) 2015-2017 DxLibEx project
  https://github.com/Nagarei/DxLibEx/

  Distributed under the Boost Software License, Version 1.0.
  (See http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
#ifndef DXLE_INC_MATH_COPYSIGN_HPP_
#define DXLE_INC_MATH_COPYSIGN_HPP_
#include "dxlibex/config/defines.h"
#include <cmath>
#include "dxlibex/math/isnan.hpp"
#include <type_traits>
#include <limits>
#include "dxlibex/type_traits/float_promote.hpp"
#ifdef DXLE_NO_CXX11_CONSTEXPR
namespace dxle{
    namespace math{
        using std::copysign;
    }
    using dxle::math::copysign;
}
#else //DXLE_NO_CXX11_CONSTEXPR
namespace dxle {
    namespace math {
        namespace detail {
            template<typename FloatType> inline DXLE_CONSTEXPR bool broken_signbit(FloatType x) DXLE_NOEXCEPT_OR_NOTHROW
            {
                return !dxle::math::isnan(x) && x < 0;
            }
        }   // namespace detail
        //
        // copysign
        //
        // issue:
        //  copysign(±x, -0) returns -x for |x| is not 0 .
        //      # returns +x . ( same as copysign(±x, +0) )
        //  copysign(±x, -NaN) returns -x for |x| is not NaN .
        //      # returns +x . ( same as copysign(±x, +NaN) )
        //
        template<
            typename FloatType,
            enable_if_t<std::is_floating_point<FloatType>::value, std::nullptr_t> = nullptr
        >
        inline DXLE_CONSTEXPR FloatType copysign(FloatType x, FloatType y) DXLE_NOEXCEPT_OR_NOTHROW
        {
            return
                x == 0
                    ? y == 0 ? y
                        : dxle::math::detail::broken_signbit(y) ? -FloatType(0)
                        : FloatType(0)
                : dxle::math::isnan(x)
                    ? dxle::math::isnan(y) ? y
                        : dxle::math::detail::broken_signbit(y) ? -std::numeric_limits<FloatType>::quiet_NaN()
                        : std::numeric_limits<FloatType>::quiet_NaN()
                : dxle::math::detail::broken_signbit(y) != dxle::math::detail::broken_signbit(x) ? -x
                : x
                ;
        }

        template<
            typename ArithmeticType1, typename ArithmeticType2,
            enable_if_t<std::is_arithmetic<ArithmeticType1>::value && std::is_arithmetic<ArithmeticType2>::value, std::nullptr_t> = nullptr
        >
        inline DXLE_CONSTEXPR dxle::float_promote_t<ArithmeticType1, ArithmeticType2>
        copysign(ArithmeticType1 x, ArithmeticType2 y) DXLE_NOEXCEPT_OR_NOTHROW  {
            using type = dxle::float_promote_t<ArithmeticType1, ArithmeticType2>;
            return dxle::math::copysign(static_cast<type>(x), static_cast<type>(y));
        }
    }   // namespace math

    using dxle::math::copysign;
}   // namespace dxle

#endif //DXLE_NO_CXX11_CONSTEXPR
#endif //DXLE_INC_MATH_COPYSIGN_HPP_