boost/math/tools/promotion.hpp
// boost\math\tools\promotion.hpp // Copyright John Maddock 2006. // Copyright Paul A. Bristow 2006. // 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) // Promote arguments functions to allow math functions to have arguments // provided as integer OR real (floating-point, built-in or UDT) // (called ArithmeticType in functions that use promotion) // that help to reduce the risk of creating multiple instantiations. // Allows creation of an inline wrapper that forwards to a foo(RT, RT) function, // so you never get to instantiate any mixed foo(RT, IT) functions. #ifndef BOOST_MATH_PROMOTION_HPP #define BOOST_MATH_PROMOTION_HPP #ifdef _MSC_VER #pragma once #endif #include <boost/math/tools/config.hpp> #include <type_traits> namespace boost { namespace math { namespace tools { // If either T1 or T2 is an integer type, // pretend it was a double (for the purposes of further analysis). // Then pick the wider of the two floating-point types // as the actual signature to forward to. // For example: // foo(int, short) -> double foo(double, double); // foo(int, float) -> double foo(double, double); // Note: NOT float foo(float, float) // foo(int, double) -> foo(double, double); // foo(double, float) -> double foo(double, double); // foo(double, float) -> double foo(double, double); // foo(any-int-or-float-type, long double) -> foo(long double, long double); // but ONLY float foo(float, float) is unchanged. // So the only way to get an entirely float version is to call foo(1.F, 2.F), // But since most (all?) the math functions convert to double internally, // probably there would not be the hoped-for gain by using float here. // This follows the C-compatible conversion rules of pow, etc // where pow(int, float) is converted to pow(double, double). template <class T> struct promote_arg { // If T is integral type, then promote to double. using type = typename std::conditional<std::is_integral<T>::value, double, T>::type; }; // These full specialisations reduce std::conditional usage and speed up // compilation: template <> struct promote_arg<float> { using type = float; }; template <> struct promote_arg<double>{ using type = double; }; template <> struct promote_arg<long double> { using type = long double; }; template <> struct promote_arg<int> { using type = double; }; template <typename T> using promote_arg_t = typename promote_arg<T>::type; template <class T1, class T2> struct promote_args_2 { // Promote, if necessary, & pick the wider of the two floating-point types. // for both parameter types, if integral promote to double. using T1P = typename promote_arg<T1>::type; // T1 perhaps promoted. using T2P = typename promote_arg<T2>::type; // T2 perhaps promoted. using type = typename std::conditional< std::is_floating_point<T1P>::value && std::is_floating_point<T2P>::value, // both T1P and T2P are floating-point? #ifdef BOOST_MATH_USE_FLOAT128 typename std::conditional<std::is_same<__float128, T1P>::value || std::is_same<__float128, T2P>::value, // either long double? __float128, #endif typename std::conditional<std::is_same<long double, T1P>::value || std::is_same<long double, T2P>::value, // either long double? long double, // then result type is long double. typename std::conditional<std::is_same<double, T1P>::value || std::is_same<double, T2P>::value, // either double? double, // result type is double. float // else result type is float. >::type #ifdef BOOST_MATH_USE_FLOAT128 >::type #endif >::type, // else one or the other is a user-defined type: typename std::conditional<!std::is_floating_point<T2P>::value && std::is_convertible<T1P, T2P>::value, T2P, T1P>::type>::type; }; // promote_arg2 // These full specialisations reduce std::conditional usage and speed up // compilation: template <> struct promote_args_2<float, float> { using type = float; }; template <> struct promote_args_2<double, double>{ using type = double; }; template <> struct promote_args_2<long double, long double> { using type = long double; }; template <> struct promote_args_2<int, int> { using type = double; }; template <> struct promote_args_2<int, float> { using type = double; }; template <> struct promote_args_2<float, int> { using type = double; }; template <> struct promote_args_2<int, double> { using type = double; }; template <> struct promote_args_2<double, int> { using type = double; }; template <> struct promote_args_2<int, long double> { using type = long double; }; template <> struct promote_args_2<long double, int> { using type = long double; }; template <> struct promote_args_2<float, double> { using type = double; }; template <> struct promote_args_2<double, float> { using type = double; }; template <> struct promote_args_2<float, long double> { using type = long double; }; template <> struct promote_args_2<long double, float> { using type = long double; }; template <> struct promote_args_2<double, long double> { using type = long double; }; template <> struct promote_args_2<long double, double> { using type = long double; }; template <typename T, typename U> using promote_args_2_t = typename promote_args_2<T, U>::type; template <class T1, class T2=float, class T3=float, class T4=float, class T5=float, class T6=float> struct promote_args { using type = typename promote_args_2< typename std::remove_cv<T1>::type, typename promote_args_2< typename std::remove_cv<T2>::type, typename promote_args_2< typename std::remove_cv<T3>::type, typename promote_args_2< typename std::remove_cv<T4>::type, typename promote_args_2< typename std::remove_cv<T5>::type, typename std::remove_cv<T6>::type >::type >::type >::type >::type >::type; #if defined(BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS) // // Guard against use of long double if it's not supported: // static_assert((0 == std::is_same<type, long double>::value), "Sorry, but this platform does not have sufficient long double support for the special functions to be reliably implemented."); #endif }; template <class T1, class T2=float, class T3=float, class T4=float, class T5=float, class T6=float> using promote_args_t = typename promote_args<T1, T2, T3, T4, T5, T6>::type; // // This struct is the same as above, but has no static assert on long double usage, // it should be used only on functions that can be implemented for long double // even when std lib support is missing or broken for that type. // template <class T1, class T2=float, class T3=float, class T4=float, class T5=float, class T6=float> struct promote_args_permissive { using type = typename promote_args_2< typename std::remove_cv<T1>::type, typename promote_args_2< typename std::remove_cv<T2>::type, typename promote_args_2< typename std::remove_cv<T3>::type, typename promote_args_2< typename std::remove_cv<T4>::type, typename promote_args_2< typename std::remove_cv<T5>::type, typename std::remove_cv<T6>::type >::type >::type >::type >::type >::type; }; template <class T1, class T2=float, class T3=float, class T4=float, class T5=float, class T6=float> using promote_args_permissive_t = typename promote_args_permissive<T1, T2, T3, T4, T5, T6>::type; } // namespace tools } // namespace math } // namespace boost #endif // BOOST_MATH_PROMOTION_HPP