1 // boost\math\tools\promotion.hpp 2 3 // Copyright John Maddock 2006. 4 // Copyright Paul A. Bristow 2006. 5 6 // Use, modification and distribution are subject to the 7 // Boost Software License, Version 1.0. 8 // (See accompanying file LICENSE_1_0.txt 9 // or copy at http://www.boost.org/LICENSE_1_0.txt) 10 11 // Promote arguments functions to allow math functions to have arguments 12 // provided as integer OR real (floating-point, built-in or UDT) 13 // (called ArithmeticType in functions that use promotion) 14 // that help to reduce the risk of creating multiple instantiations. 15 // Allows creation of an inline wrapper that forwards to a foo(RT, RT) function, 16 // so you never get to instantiate any mixed foo(RT, IT) functions. 17 18 #ifndef BOOST_MATH_PROMOTION_HPP 19 #define BOOST_MATH_PROMOTION_HPP 20 21 #ifdef _MSC_VER 22 #pragma once 23 #endif 24 25 // Boost type traits: 26 #include <boost/math/tools/config.hpp> 27 #include <boost/type_traits/is_floating_point.hpp> // for boost::is_floating_point; 28 #include <boost/type_traits/is_integral.hpp> // for boost::is_integral 29 #include <boost/type_traits/is_convertible.hpp> // for boost::is_convertible 30 #include <boost/type_traits/is_same.hpp>// for boost::is_same 31 #include <boost/type_traits/remove_cv.hpp>// for boost::remove_cv 32 // Boost Template meta programming: 33 #include <boost/mpl/if.hpp> // for boost::mpl::if_c. 34 #include <boost/mpl/and.hpp> // for boost::mpl::if_c. 35 #include <boost/mpl/or.hpp> // for boost::mpl::if_c. 36 #include <boost/mpl/not.hpp> // for boost::mpl::if_c. 37 38 #ifdef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS 39 #include <boost/static_assert.hpp> 40 #endif 41 42 namespace boost 43 { 44 namespace math 45 { 46 namespace tools 47 { 48 // If either T1 or T2 is an integer type, 49 // pretend it was a double (for the purposes of further analysis). 50 // Then pick the wider of the two floating-point types 51 // as the actual signature to forward to. 52 // For example: 53 // foo(int, short) -> double foo(double, double); 54 // foo(int, float) -> double foo(double, double); 55 // Note: NOT float foo(float, float) 56 // foo(int, double) -> foo(double, double); 57 // foo(double, float) -> double foo(double, double); 58 // foo(double, float) -> double foo(double, double); 59 // foo(any-int-or-float-type, long double) -> foo(long double, long double); 60 // but ONLY float foo(float, float) is unchanged. 61 // So the only way to get an entirely float version is to call foo(1.F, 2.F), 62 // But since most (all?) the math functions convert to double internally, 63 // probably there would not be the hoped-for gain by using float here. 64 65 // This follows the C-compatible conversion rules of pow, etc 66 // where pow(int, float) is converted to pow(double, double). 67 68 template <class T> 69 struct promote_arg 70 { // If T is integral type, then promote to double. 71 typedef typename mpl::if_<is_integral<T>, double, T>::type type; 72 }; 73 // These full specialisations reduce mpl::if_ usage and speed up 74 // compilation: 75 template <> struct promote_arg<float> { typedef float type; }; 76 template <> struct promote_arg<double>{ typedef double type; }; 77 template <> struct promote_arg<long double> { typedef long double type; }; 78 template <> struct promote_arg<int> { typedef double type; }; 79 80 template <class T1, class T2> 81 struct promote_args_2 82 { // Promote, if necessary, & pick the wider of the two floating-point types. 83 // for both parameter types, if integral promote to double. 84 typedef typename promote_arg<T1>::type T1P; // T1 perhaps promoted. 85 typedef typename promote_arg<T2>::type T2P; // T2 perhaps promoted. 86 87 typedef typename mpl::if_< 88 typename mpl::and_<is_floating_point<T1P>, is_floating_point<T2P> >::type, // both T1P and T2P are floating-point? 89 typename mpl::if_< typename mpl::or_<is_same<long double, T1P>, is_same<long double, T2P> >::type, // either long double? 90 long double, // then result type is long double. 91 typename mpl::if_< typename mpl::or_<is_same<double, T1P>, is_same<double, T2P> >::type, // either double? 92 double, // result type is double. 93 float // else result type is float. 94 >::type 95 >::type, 96 // else one or the other is a user-defined type: 97 typename mpl::if_< typename mpl::and_<mpl::not_<is_floating_point<T2P> >, ::boost::is_convertible<T1P, T2P> >, T2P, T1P>::type>::type type; 98 }; // promote_arg2 99 // These full specialisations reduce mpl::if_ usage and speed up 100 // compilation: 101 template <> struct promote_args_2<float, float> { typedef float type; }; 102 template <> struct promote_args_2<double, double>{ typedef double type; }; 103 template <> struct promote_args_2<long double, long double> { typedef long double type; }; 104 template <> struct promote_args_2<int, int> { typedef double type; }; 105 template <> struct promote_args_2<int, float> { typedef double type; }; 106 template <> struct promote_args_2<float, int> { typedef double type; }; 107 template <> struct promote_args_2<int, double> { typedef double type; }; 108 template <> struct promote_args_2<double, int> { typedef double type; }; 109 template <> struct promote_args_2<int, long double> { typedef long double type; }; 110 template <> struct promote_args_2<long double, int> { typedef long double type; }; 111 template <> struct promote_args_2<float, double> { typedef double type; }; 112 template <> struct promote_args_2<double, float> { typedef double type; }; 113 template <> struct promote_args_2<float, long double> { typedef long double type; }; 114 template <> struct promote_args_2<long double, float> { typedef long double type; }; 115 template <> struct promote_args_2<double, long double> { typedef long double type; }; 116 template <> struct promote_args_2<long double, double> { typedef long double type; }; 117 118 template <class T1, class T2=float, class T3=float, class T4=float, class T5=float, class T6=float> 119 struct promote_args 120 { 121 typedef typename promote_args_2< 122 typename remove_cv<T1>::type, 123 typename promote_args_2< 124 typename remove_cv<T2>::type, 125 typename promote_args_2< 126 typename remove_cv<T3>::type, 127 typename promote_args_2< 128 typename remove_cv<T4>::type, 129 typename promote_args_2< 130 typename remove_cv<T5>::type, typename remove_cv<T6>::type 131 >::type 132 >::type 133 >::type 134 >::type 135 >::type type; 136 137 #ifdef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS 138 // 139 // Guard against use of long double if it's not supported: 140 // 141 BOOST_STATIC_ASSERT((0 == ::boost::is_same<type, long double>::value)); 142 #endif 143 }; 144 145 } // namespace tools 146 } // namespace math 147 } // namespace boost 148 149 #endif // BOOST_MATH_PROMOTION_HPP 150 151
