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