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2019-03-29 39bc0caa2ac9acbae9a1a1217dc08704d96737c0

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#ifndef _APPLY_TUPLE_H_
#define _APPLY_TUPLE_H_
 
#include <stddef.h>
#include <tuple>
#include <type_traits>
#include <utility>
 
#if __cplusplus < 201703L
 
namespace detail
{
    template<size_t N>
    struct apply 
    {
        template<typename F, typename T, typename... A>
        static inline auto apply_tuple(F&& f, T&& t, A&&... a)
            -> decltype(apply<N-1>::apply_tuple(
            std::forward<F>(f), std::forward<T>(t),
            std::get<N-1>(std::forward<T>(t)), std::forward<A>(a)...
            ))
        {
            return apply<N-1>::apply_tuple(std::forward<F>(f), std::forward<T>(t),
                std::get<N-1>(std::forward<T>(t)), std::forward<A>(a)...
                );
        }
    };
 
    template<>
    struct apply<0> 
    {
        template<typename F, typename T, typename... A>
        static inline typename std::result_of<F(A...)>::type apply_tuple(F&& f, T&&, A&&... a)
        {
            return std::forward<F>(f)(std::forward<A>(a)...);
        }
    };
}
 
template<typename F, typename T>
inline auto apply_tuple(F&& f, T&& t)
    -> decltype(detail::apply< std::tuple_size<
        typename std::decay<T>::type
    >::value>::apply_tuple(std::forward<F>(f), std::forward<T>(t)))
{
    return detail::apply< std::tuple_size<
        typename std::decay<T>::type
    >::value>::apply_tuple(std::forward<F>(f), std::forward<T>(t));
}
 
#else
 
template <class F, class Tuple>
inline constexpr decltype(auto) apply_tuple(F&& f, Tuple&& t)
{
    return std::apply(std;:forward<F>(f), std::forward<Tuple>(t));
}
 
#endif // C++17
 
#endif //_APPLY_TUPLE_H_