Sprout/sprout/math/fdim.hpp

/*=============================================================================
  Copyright (c) 2011-2013 Bolero MURAKAMI
  https://github.com/bolero-MURAKAMI/Sprout

  Distributed under 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)
=============================================================================*/
#ifndef SPROUT_MATH_FDIM_HPP
#define SPROUT_MATH_FDIM_HPP

#include <type_traits>
#include <sprout/config.hpp>
#include <sprout/limits.hpp>
#include <sprout/math/detail/config.hpp>
#include <sprout/math/isnan.hpp>
#include <sprout/type_traits/float_promote.hpp>
#include <sprout/type_traits/enabler_if.hpp>

namespace sprout {
	namespace math {
		namespace detail {
			template<
				typename FloatType,
				typename sprout::enabler_if<std::is_floating_point<FloatType>::value>::type = sprout::enabler
			>
			inline SPROUT_CONSTEXPR FloatType
			fdim(FloatType x, FloatType y) {
				return sprout::math::isnan(y) ? y
					: sprout::math::isnan(x) ? x
					: x == sprout::numeric_limits<FloatType>::infinity() ? sprout::numeric_limits<FloatType>::infinity()
					: x == -sprout::numeric_limits<FloatType>::infinity() ? FloatType(0)
					: y == sprout::numeric_limits<FloatType>::infinity() ? FloatType(0)
					: y == -sprout::numeric_limits<FloatType>::infinity() ? sprout::numeric_limits<FloatType>::infinity()
#if SPROUT_USE_BUILTIN_CMATH_FUNCTION
					: std::fdim(x, y)
#else
					: x > y ? x - y : FloatType(0)
#endif
					;
			}
			template<
				typename ArithmeticType1,
				typename ArithmeticType2,
				typename sprout::enabler_if<
					std::is_arithmetic<ArithmeticType1>::value && std::is_arithmetic<ArithmeticType2>::value
				>::type = sprout::enabler
			>
			inline SPROUT_CONSTEXPR typename sprout::float_promote<ArithmeticType1, ArithmeticType2>::type
			fdim(ArithmeticType1 x, ArithmeticType2 y) {
				typedef typename sprout::float_promote<ArithmeticType1, ArithmeticType2>::type type;
				return sprout::math::detail::fdim(static_cast<type>(x), static_cast<type>(y));
			}
		}	// namespace detail

		using sprout::math::detail::fdim;
	}	// namespace math

	using sprout::math::fdim;
}	// namespace sprout

#endif	// #ifndef SPROUT_MATH_FDIM_HPP