Chris@16: // boost\math\tools\promotion.hpp
Chris@16: 
Chris@16: // Copyright John Maddock 2006.
Chris@16: // Copyright Paul A. Bristow 2006.
Chris@16: 
Chris@16: // Use, modification and distribution are subject to the
Chris@16: // Boost Software License, Version 1.0.
Chris@16: // (See accompanying file LICENSE_1_0.txt
Chris@16: // or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: // Promote arguments functions to allow math functions to have arguments
Chris@16: // provided as integer OR real (floating-point, built-in or UDT)
Chris@16: // (called ArithmeticType in functions that use promotion)
Chris@16: // that help to reduce the risk of creating multiple instantiations.
Chris@16: // Allows creation of an inline wrapper that forwards to a foo(RT, RT) function,
Chris@16: // so you never get to instantiate any mixed foo(RT, IT) functions.
Chris@16: 
Chris@16: #ifndef BOOST_MATH_PROMOTION_HPP
Chris@16: #define BOOST_MATH_PROMOTION_HPP
Chris@16: 
Chris@16: #ifdef _MSC_VER
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: // Boost type traits:
Chris@16: #include <boost/math/tools/config.hpp>
Chris@16: #include <boost/type_traits/is_floating_point.hpp> // for boost::is_floating_point;
Chris@16: #include <boost/type_traits/is_integral.hpp> // for boost::is_integral
Chris@16: #include <boost/type_traits/is_convertible.hpp> // for boost::is_convertible
Chris@16: #include <boost/type_traits/is_same.hpp>// for boost::is_same
Chris@16: #include <boost/type_traits/remove_cv.hpp>// for boost::remove_cv
Chris@16: // Boost Template meta programming:
Chris@16: #include <boost/mpl/if.hpp> // for boost::mpl::if_c.
Chris@16: #include <boost/mpl/and.hpp> // for boost::mpl::if_c.
Chris@16: #include <boost/mpl/or.hpp> // for boost::mpl::if_c.
Chris@16: #include <boost/mpl/not.hpp> // for boost::mpl::if_c.
Chris@16: 
Chris@16: #ifdef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
Chris@16: #include <boost/static_assert.hpp>
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost
Chris@16: {
Chris@16:   namespace math
Chris@16:   {
Chris@16:     namespace tools
Chris@16:     {
Chris@16:       // If either T1 or T2 is an integer type,
Chris@16:       // pretend it was a double (for the purposes of further analysis).
Chris@16:       // Then pick the wider of the two floating-point types
Chris@16:       // as the actual signature to forward to.
Chris@16:       // For example:
Chris@16:       // foo(int, short) -> double foo(double, double);
Chris@16:       // foo(int, float) -> double foo(double, double);
Chris@16:       // Note: NOT float foo(float, float)
Chris@16:       // foo(int, double) -> foo(double, double);
Chris@16:       // foo(double, float) -> double foo(double, double);
Chris@16:       // foo(double, float) -> double foo(double, double);
Chris@16:       // foo(any-int-or-float-type, long double) -> foo(long double, long double);
Chris@16:       // but ONLY float foo(float, float) is unchanged.
Chris@16:       // So the only way to get an entirely float version is to call foo(1.F, 2.F),
Chris@16:       // But since most (all?) the math functions convert to double internally,
Chris@16:       // probably there would not be the hoped-for gain by using float here.
Chris@16: 
Chris@16:       // This follows the C-compatible conversion rules of pow, etc
Chris@16:       // where pow(int, float) is converted to pow(double, double).
Chris@16: 
Chris@16:       template <class T>
Chris@16:       struct promote_arg
Chris@16:       { // If T is integral type, then promote to double.
Chris@16:         typedef typename mpl::if_<is_integral<T>, double, T>::type type;
Chris@16:       };
Chris@16:       // These full specialisations reduce mpl::if_ usage and speed up
Chris@16:       // compilation:
Chris@16:       template <> struct promote_arg<float> { typedef float type; };
Chris@16:       template <> struct promote_arg<double>{ typedef double type; };
Chris@16:       template <> struct promote_arg<long double> { typedef long double type; };
Chris@16:       template <> struct promote_arg<int> {  typedef double type; };
Chris@16: 
Chris@16:       template <class T1, class T2>
Chris@16:       struct promote_args_2
Chris@16:       { // Promote, if necessary, & pick the wider of the two floating-point types.
Chris@16:         // for both parameter types, if integral promote to double.
Chris@16:         typedef typename promote_arg<T1>::type T1P; // T1 perhaps promoted.
Chris@16:         typedef typename promote_arg<T2>::type T2P; // T2 perhaps promoted.
Chris@16: 
Chris@16:         typedef typename mpl::if_<
Chris@16:           typename mpl::and_<is_floating_point<T1P>, is_floating_point<T2P> >::type, // both T1P and T2P are floating-point?
Chris@16:           typename mpl::if_< typename mpl::or_<is_same<long double, T1P>, is_same<long double, T2P> >::type, // either long double?
Chris@16:             long double, // then result type is long double.
Chris@16:             typename mpl::if_< typename mpl::or_<is_same<double, T1P>, is_same<double, T2P> >::type, // either double?
Chris@16:             double, // result type is double.
Chris@16:           float // else result type is float.
Chris@16:           >::type
Chris@16:           >::type,
Chris@16:           // else one or the other is a user-defined type:
Chris@16:           typename mpl::if_< typename mpl::and_<mpl::not_<is_floating_point<T2P> >, ::boost::is_convertible<T1P, T2P> >, T2P, T1P>::type>::type type;
Chris@16:       }; // promote_arg2
Chris@16:       // These full specialisations reduce mpl::if_ usage and speed up
Chris@16:       // compilation:
Chris@16:       template <> struct promote_args_2<float, float> { typedef float type; };
Chris@16:       template <> struct promote_args_2<double, double>{ typedef double type; };
Chris@16:       template <> struct promote_args_2<long double, long double> { typedef long double type; };
Chris@16:       template <> struct promote_args_2<int, int> {  typedef double type; };
Chris@16:       template <> struct promote_args_2<int, float> {  typedef double type; };
Chris@16:       template <> struct promote_args_2<float, int> {  typedef double type; };
Chris@16:       template <> struct promote_args_2<int, double> {  typedef double type; };
Chris@16:       template <> struct promote_args_2<double, int> {  typedef double type; };
Chris@16:       template <> struct promote_args_2<int, long double> {  typedef long double type; };
Chris@16:       template <> struct promote_args_2<long double, int> {  typedef long double type; };
Chris@16:       template <> struct promote_args_2<float, double> {  typedef double type; };
Chris@16:       template <> struct promote_args_2<double, float> {  typedef double type; };
Chris@16:       template <> struct promote_args_2<float, long double> {  typedef long double type; };
Chris@16:       template <> struct promote_args_2<long double, float> {  typedef long double type; };
Chris@16:       template <> struct promote_args_2<double, long double> {  typedef long double type; };
Chris@16:       template <> struct promote_args_2<long double, double> {  typedef long double type; };
Chris@16: 
Chris@16:       template <class T1, class T2=float, class T3=float, class T4=float, class T5=float, class T6=float>
Chris@16:       struct promote_args
Chris@16:       {
Chris@16:          typedef typename promote_args_2<
Chris@16:             typename remove_cv<T1>::type,
Chris@16:             typename promote_args_2<
Chris@16:                typename remove_cv<T2>::type,
Chris@16:                typename promote_args_2<
Chris@16:                   typename remove_cv<T3>::type,
Chris@16:                   typename promote_args_2<
Chris@16:                      typename remove_cv<T4>::type,
Chris@16:                      typename promote_args_2<
Chris@16:                         typename remove_cv<T5>::type, typename remove_cv<T6>::type
Chris@16:                      >::type
Chris@16:                   >::type
Chris@16:                >::type
Chris@16:             >::type
Chris@16:          >::type type;
Chris@16: 
Chris@16: #ifdef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
Chris@16:          //
Chris@16:          // Guard against use of long double if it's not supported:
Chris@16:          //
Chris@16:          BOOST_STATIC_ASSERT_MSG((0 == ::boost::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.");
Chris@16: #endif
Chris@16:       };
Chris@16: 
Chris@16:       //
Chris@16:       // This struct is the same as above, but has no static assert on long double usage,
Chris@16:       // it should be used only on functions that can be implemented for long double
Chris@16:       // even when std lib support is missing or broken for that type.
Chris@16:       //
Chris@16:       template <class T1, class T2=float, class T3=float, class T4=float, class T5=float, class T6=float>
Chris@16:       struct promote_args_permissive
Chris@16:       {
Chris@16:          typedef typename promote_args_2<
Chris@16:             typename remove_cv<T1>::type,
Chris@16:             typename promote_args_2<
Chris@16:                typename remove_cv<T2>::type,
Chris@16:                typename promote_args_2<
Chris@16:                   typename remove_cv<T3>::type,
Chris@16:                   typename promote_args_2<
Chris@16:                      typename remove_cv<T4>::type,
Chris@16:                      typename promote_args_2<
Chris@16:                         typename remove_cv<T5>::type, typename remove_cv<T6>::type
Chris@16:                      >::type
Chris@16:                   >::type
Chris@16:                >::type
Chris@16:             >::type
Chris@16:          >::type type;
Chris@16:       };
Chris@16: 
Chris@16:     } // namespace tools
Chris@16:   } // namespace math
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif // BOOST_MATH_PROMOTION_HPP
Chris@16: