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 // Boost type traits: #include <boost/math/tools/config.hpp> #include <boost/type_traits/is_floating_point.hpp> // for boost::is_floating_point; #include <boost/type_traits/is_integral.hpp> // for boost::is_integral #include <boost/type_traits/is_convertible.hpp> // for boost::is_convertible #include <boost/type_traits/is_same.hpp>// for boost::is_same #include <boost/type_traits/remove_cv.hpp>// for boost::remove_cv // Boost Template meta programming: #include <boost/mpl/if.hpp> // for boost::mpl::if_c. #include <boost/mpl/and.hpp> // for boost::mpl::if_c. #include <boost/mpl/or.hpp> // for boost::mpl::if_c. #ifdef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS #include <boost/static_assert.hpp> #endif 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. typedef typename mpl::if_<is_integral<T>, double, T>::type type; }; // These full specialisations reduce mpl::if_ usage and speed up // compilation: template <> struct promote_arg<float> { typedef float type; }; template <> struct promote_arg<double>{ typedef double type; }; template <> struct promote_arg<long double> { typedef long double type; }; template <> struct promote_arg<int> { typedef double 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. typedef typename promote_arg<T1>::type T1P; // T1 perhaps promoted. typedef typename promote_arg<T2>::type T2P; // T2 perhaps promoted. typedef typename mpl::if_< typename mpl::and_<is_floating_point<T1P>, is_floating_point<T2P> >::type, // both T1P and T2P are floating-point? typename mpl::if_< typename mpl::or_<is_same<long double, T1P>, is_same<long double, T2P> >::type, // either long double? long double, // then result type is long double. typename mpl::if_< typename mpl::or_<is_same<double, T1P>, is_same<double, T2P> >::type, // either double? double, // result type is double. float // else result type is float. >::type >::type, // else one or the other is a user-defined type: typename mpl::if_< ::boost::is_convertible<T1P, T2P>, T2P, T1P>::type>::type type; }; // promote_arg2 // These full specialisations reduce mpl::if_ usage and speed up // compilation: template <> struct promote_args_2<float, float> { typedef float type; }; template <> struct promote_args_2<double, double>{ typedef double type; }; template <> struct promote_args_2<long double, long double> { typedef long double type; }; template <> struct promote_args_2<int, int> { typedef double type; }; template <> struct promote_args_2<int, float> { typedef double type; }; template <> struct promote_args_2<float, int> { typedef double type; }; template <> struct promote_args_2<int, double> { typedef double type; }; template <> struct promote_args_2<double, int> { typedef double type; }; template <> struct promote_args_2<int, long double> { typedef long double type; }; template <> struct promote_args_2<long double, int> { typedef long double type; }; template <> struct promote_args_2<float, double> { typedef double type; }; template <> struct promote_args_2<double, float> { typedef double type; }; template <> struct promote_args_2<float, long double> { typedef long double type; }; template <> struct promote_args_2<long double, float> { typedef long double type; }; template <> struct promote_args_2<double, long double> { typedef long double type; }; template <> struct promote_args_2<long double, double> { typedef long double type; }; template <class T1, class T2=float, class T3=float, class T4=float, class T5=float, class T6=float> struct promote_args { typedef typename promote_args_2< typename remove_cv<T1>::type, typename promote_args_2< typename remove_cv<T2>::type, typename promote_args_2< typename remove_cv<T3>::type, typename promote_args_2< typename remove_cv<T4>::type, typename promote_args_2< typename remove_cv<T5>::type, typename remove_cv<T6>::type >::type >::type >::type >::type >::type type; #ifdef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS // // Guard against use of long double if it's not supported: // BOOST_STATIC_ASSERT((0 == ::boost::is_same<type, long double>::value)); #endif }; } // namespace tools } // namespace math } // namespace boost #endif // BOOST_MATH_PROMOTION_HPP