//	Distributed under the Boost Software License Version 1.0 https://www.boost.org/LICENSE_1_0.txt
//	Copyright Gero Peterhoff

#ifndef BOOST_MATH_CCMATH_SIGNBIT_HPP
#define BOOST_MATH_CCMATH_SIGNBIT_HPP

#include <cmath>
#include <type_traits>
#include <boost/type_traits/is_floating_point_more.hpp>
#include <boost/math/tools/is_constant_evaluated.hpp>
#include <boost/type_traits/dependent_false.hpp>
#include <boost/math/ccmath/bits.hpp>



namespace boost::math::ccmath
{
namespace detail
{
template <typename T>
inline constexpr bool	signbit_impl(const T arg)	noexcept
{
	if constexpr (boost::is_float128_v<T>)
	{
		const auto bits = BOOST_MATH_BIT_CAST(float128_bits, arg);
		return bits.sign;
	}
	else if constexpr (boost::is_float80_v<T>)
	{
		if constexpr (sizeof(T) == 16)
		{
			const auto bits = BOOST_MATH_BIT_CAST(float80_bits_128, arg);
			return bits.sign;
		}
		else if constexpr (sizeof(T) == 12)
		{
			const auto bits = BOOST_MATH_BIT_CAST(float80_bits_96, arg);
			return bits.sign;
		}
		else if constexpr (sizeof(T) == 10)
		{
			const auto bits = BOOST_MATH_BIT_CAST(float80_bits_80, arg);
			return bits.sign;
		}
		else
		{
			static_assert(boost::dependent_false_v<T>, "signbit is not supported with this type or platform");
			return false;
		}
	}
	else if constexpr (boost::is_float64_v<T>)
	{
		const auto bits = BOOST_MATH_BIT_CAST(float64_bits, arg);
		return bits.sign;
	}
	else if constexpr (boost::is_float32_v<T>)
	{
		const auto bits = BOOST_MATH_BIT_CAST(float32_bits, arg);
		return bits.sign;
	}
	else if constexpr (boost::is_float16_v<T>)
	{
		const auto bits = BOOST_MATH_BIT_CAST(float16_bits, arg);
		return bits.sign;
	}
	else if constexpr (boost::is_bfloat16_v<T>)
	{
		const auto bits = BOOST_MATH_BIT_CAST(bfloat16_bits, arg);
		return bits.sign;
	}
	else
	{
		static_assert(boost::dependent_false_v<T>, "signbit is not supported with this type or platform");
		return false;
	}
}

}	//	detail



template <typename T>
constexpr bool	signbit(const T x)	noexcept
{
	BOOST_IF_CONSTEXPR (std::is_arithmetic_v<T>)
	{
		if (BOOST_MATH_IS_CONSTANT_EVALUATED(x))
		{
			BOOST_IF_CONSTEXPR (std::is_integral_v<T>)
			{
				return x < T(0);
			}
			else
			{
				return detail::signbit_impl(x);
			}
		}
		else
		{
			return std::signbit(x);
		}
	}
	else
	{
		static_assert(boost::dependent_false_v<T>, "signbit is not supported with this type or platform");
		return 0;
	}
}

}	//	boost::math::ccmath

#endif // BOOST_MATH_CCMATH_SIGNBIT_HPP