function_traits.h

#include <cinttypes>
#include <tuple>

template<class>
struct function_traits {};

template<class R, class... Args>
struct function_traits<R(Args...)> {
	typedef R                   ret_t;
	typedef std::tuple<Args...> args_t;
		std::size_t         n_args = std::tuple_size<args_t>::value;

	typedef std::tuple<
			std::remove_cv_t<
				std::remove_reference_t<
					std::remove_pointer_t<
						std::remove_all_extents_t<Args>>>>...> args_pure_t;

	template<std::size_t N>
	struct arg { typedef std::tuple_element_t<N, args_t> type; };
	
	template<std::size_t N>
	using arg_t = typename arg<N>::type;


	template<std::size_t N>
	struct arg_pure { typedef std::tuple_element_t<N, args_pure_t> type; };

	template<std::size_t N>
	using arg_pure_t = typename arg_pure<N>::type;
};

I don't know what the fuck is this '-'