math/ccmath/hypot.hpp

0001 //  (C) Copyright John Maddock 2005-2021.
0002 //  (C) Copyright Matt Borland 2021.
0003 //  Use, modification and distribution are subject to the
0004 //  Boost Software License, Version 1.0. (See accompanying file
0005 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006
0007 #ifndef BOOST_MATH_CCMATH_HYPOT_HPP
0008 #define BOOST_MATH_CCMATH_HYPOT_HPP
0009
0010 #include <boost/math/ccmath/detail/config.hpp>
0011
0012 #ifdef BOOST_MATH_NO_CCMATH
0013 #error "The header <boost/math/hypot.hpp> can only be used in C++17 and later."
0014 #endif
0015
0016 #include <array>
0017 #include <boost/math/tools/config.hpp>
0018 #include <boost/math/tools/promotion.hpp>
0019 #include <boost/math/ccmath/sqrt.hpp>
0020 #include <boost/math/ccmath/abs.hpp>
0021 #include <boost/math/ccmath/isinf.hpp>
0022 #include <boost/math/ccmath/isnan.hpp>
0023 #include <boost/math/ccmath/detail/swap.hpp>
0024
0025 namespace boost::math::ccmath {
0026
0027 namespace detail {
0028
0029 template <typename T>
0030 constexpr T hypot_impl(T x, T y) noexcept
0031 {
0032     x = boost::math::ccmath::abs(x);
0033     y = boost::math::ccmath::abs(y);
0034
0035     if (y > x)
0036     {
0037         boost::math::ccmath::detail::swap(x, y);
0038     }
0039
0040     if(x * std::numeric_limits<T>::epsilon() >= y)
0041     {
0042         return x;
0043     }
0044
0045     T rat = y / x;
0046     return x * boost::math::ccmath::sqrt(1 + rat * rat);
0047 }
0048
0049 } // Namespace detail
0050
0051 template <typename Real, std::enable_if_t<!std::is_integral_v<Real>, bool> = true>
0052 constexpr Real hypot(Real x, Real y) noexcept
0053 {
0054     if(BOOST_MATH_IS_CONSTANT_EVALUATED(x))
0055     {
0056         if (boost::math::ccmath::abs(x) == static_cast<Real>(0))
0057         {
0058             return boost::math::ccmath::abs(y);
0059         }
0060         else if (boost::math::ccmath::abs(y) == static_cast<Real>(0))
0061         {
0062             return boost::math::ccmath::abs(x);
0063         }
0064         // Return +inf even if the other argument is NaN
0065         else if (boost::math::ccmath::isinf(x) || boost::math::ccmath::isinf(y))
0066         {
0067             return std::numeric_limits<Real>::infinity();
0068         }
0069         else if (boost::math::ccmath::isnan(x))
0070         {
0071             return x;
0072         }
0073         else if (boost::math::ccmath::isnan(y))
0074         {
0075             return y;
0076         }
0077
0078         return boost::math::ccmath::detail::hypot_impl(x, y);
0079     }
0080     else
0081     {
0082         using std::hypot;
0083         return hypot(x, y);
0084     }
0085 }
0086
0087 template <typename T1, typename T2>
0088 constexpr auto hypot(T1 x, T2 y) noexcept
0089 {
0090     if(BOOST_MATH_IS_CONSTANT_EVALUATED(x))
0091     {
0092         using promoted_type = boost::math::tools::promote_args_2_t<T1, T2>;
0093         return boost::math::ccmath::hypot(static_cast<promoted_type>(x), static_cast<promoted_type>(y));
0094     }
0095     else
0096     {
0097         using std::hypot;
0098         return hypot(x, y);
0099     }
0100 }
0101
0102 constexpr float hypotf(float x, float y) noexcept
0103 {
0104     return boost::math::ccmath::hypot(x, y);
0105 }
0106
0107 #ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
0108 constexpr long double hypotl(long double x, long double y) noexcept
0109 {
0110     return boost::math::ccmath::hypot(x, y);
0111 }
0112 #endif
0113
0114 } // Namespaces
0115
0116 #endif // BOOST_MATH_CCMATH_HYPOT_HPP