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// (C) Copyright Matt Borland 2022.
// 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)
#ifndef BOOST_MATH_CCMATH_FDIM_HPP
#define BOOST_MATH_CCMATH_FDIM_HPP
#include <boost/math/ccmath/detail/config.hpp>
#ifdef BOOST_MATH_NO_CCMATH
#error "The header <boost/math/fdim.hpp> can only be used in C++17 and later."
#endif
#include <boost/math/tools/promotion.hpp>
#include <boost/math/ccmath/isnan.hpp>
namespace boost::math::ccmath {
namespace detail {
template <typename T>
constexpr T fdim_impl(const T x, const T y) noexcept
{
if (x <= y)
{
return 0;
}
else if ((y < 0) && (x > (std::numeric_limits<T>::max)() + y))
{
return std::numeric_limits<T>::infinity();
}
else
{
return x - y;
}
}
} // Namespace detail
template <typename Real, std::enable_if_t<!std::is_integral_v<Real>, bool> = true>
constexpr Real fdim(Real x, Real y) noexcept
{
if (BOOST_MATH_IS_CONSTANT_EVALUATED(x))
{
if (boost::math::ccmath::isnan(x))
{
return x;
}
else if (boost::math::ccmath::isnan(y))
{
return y;
}
return boost::math::ccmath::detail::fdim_impl(x, y);
}
else
{
using std::fdim;
return fdim(x, y);
}
}
template <typename T1, typename T2>
constexpr auto fdim(T1 x, T2 y) noexcept
{
if (BOOST_MATH_IS_CONSTANT_EVALUATED(x))
{
using promoted_type = boost::math::tools::promote_args_t<T1, T2>;
return boost::math::ccmath::fdim(promoted_type(x), promoted_type(y));
}
else
{
using std::fdim;
return fdim(x, y);
}
}
constexpr float fdimf(float x, float y) noexcept
{
return boost::math::ccmath::fdim(x, y);
}
#ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
constexpr long double fdiml(long double x, long double y) noexcept
{
return boost::math::ccmath::fdim(x, y);
}
#endif
} // Namespace boost::math::ccmath
#endif // BOOST_MATH_CCMATH_FDIM_HPP
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