float_promote.hpp

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/*=============================================================================
  Copyright (C) 2015-2017 DxLibEx project
  https://github.com/Nagarei/DxLibEx/

  Distributed under the Boost Software License, Version 1.0.
  (See http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
#ifndef DXLE_TYPE_TRAITS_FLOAT_PROMOTE_HPP
#define DXLE_TYPE_TRAITS_FLOAT_PROMOTE_HPP

#include <type_traits>
#include "dxlibex/config/defines.h"
#include "dxlibex/type_traits/first_enabled.hpp"

namespace dxle {
namespace type_traits {
    namespace detail {
        template<typename T> struct float_promote1 : public std::conditional<std::is_floating_point<T>::value, T, double>
        {
            static_assert(
                std::is_arithmetic<T>::value,
                "float_promote requires arithmetic type."
            );
        };
        template<typename T, typename U, bool is_arithmetic = std::is_arithmetic<T>::value && std::is_arithmetic<U>::value>
        struct float_promote2 {
            static_assert(
                std::is_arithmetic<T>::value && std::is_arithmetic<U>::value,
                "float_promote requires arithmetic type."
                );
        };
        template<typename T, typename U>
        struct float_promote2<T, U, true>
        {
            using type = first_enabled_t<
                enable_if<(std::is_same<T, long double>::value || std::is_same<U, long double>::value), long double>,
                enable_if<(std::is_same<T, float>::value && std::is_same<U, float>::value), float>,
                double
            >;
        };

        template<typename... Types> struct float_promote_impl;
        template<typename T, typename U, typename... Tail>
        struct float_promote_impl<T, U, Tail...>
            : public dxle::type_traits::detail::float_promote_impl<
            typename dxle::type_traits::detail::float_promote2<T, U>::type,
                Tail...
            >
        {};
        template<typename T>
        struct float_promote_impl<T>
            : public dxle::type_traits::detail::float_promote1<T>
        {};
    }   // namespace detail

    //
    // float_promote
    //
    template<typename... Types>
    struct float_promote
        : public dxle::type_traits::detail::float_promote_impl<
            typename std::remove_cv<Types>::type...
        >
    {};

    template<typename... Types>
    using float_promote_t = typename dxle::float_promote<Types...>::type;
}//namespace
using namespace type_traits;
}   // namespace dxle

#endif  // #ifndef DXLE_TYPE_TRAITS_FLOAT_PROMOTE_HPP