cast_if.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_INC_ALGORITHM_CAST_IF_HPP_
#define DXLE_INC_ALGORITHM_CAST_IF_HPP_
#include "dxlibex/config/defines.h"
#include <utility>
namespace dxle {
    namespace detail {

        template<typename from, typename to, bool do_cast,
            bool is_nothrow_move_constructible =
                std::is_nothrow_move_constructible<from>::value>
        struct static_cast_if_helper{
            DXLE_CONSTEXPR to operator()(const from& n)
                const DXLE_NOEXCEPT_IF_EXPR(static_cast<double>(std::declval<from>()))
            {
                return static_cast<double>(n);
            }
        };

        template<typename from, typename to>
        struct static_cast_if_helper<to, from, false, false>{
            DXLE_CONSTEXPR to operator()(const from& n)
                const DXLE_NOEXCEPT_IF(std::is_nothrow_copy_constructible<from>::value)
            {
                return n;
            }
        };

        template<typename from, typename to>
        struct static_cast_if_helper<to, from, false, true>{

            DXLE_CONSTEXPR to operator()(const from& n)
                const DXLE_NOEXCEPT_IF(std::is_nothrow_copy_constructible<from>::value)
            {
                return n;
            }
            DXLE_CONSTEXPR to operator()(from&& n)
                const DXLE_NOEXCEPT_OR_NOTHROW
            {
                return std::move(n);
            }
        };
    }//namespace detail

    template<typename from, typename to, bool do_cast>
    DXLE_CONSTEXPR to static_cast_if(const from& n)
        DXLE_NOEXCEPT_IF_EXPR((
            dxle::detail::static_cast_if_helper<to, from, do_cast>()(
                std::move(std::declval<from>())
            )
        ))
    {
        return dxle::detail::static_cast_if_helper<from, to, do_cast>()(std::move(n));
    }

    template<typename from, typename to, bool do_cast>
    DXLE_CONSTEXPR to static_cast_if(from&& n)
        DXLE_NOEXCEPT_IF_EXPR((
            dxle::detail::static_cast_if_helper<to, from, do_cast>()(
                std::move(std::declval<from>())
            )
        ))
    {
        return dxle::detail::static_cast_if_helper<from, to, do_cast>()(std::move(n));
    }
}//namespace dxle
#endif //DXLE_INC_ALGORITHM_CAST_IF_HPP_