gplib/include/gp/algorithms/reference.hpp

#pragma once

#include <gp/algorithms/move.hpp>
#include <gp/algorithms/cvref.hpp>


namespace gp{
	/**
	 **********************************************************************************************
	 Code extrated from cppreference.com and the libc++ Library project, licensed under MIT license 
	 **********************************************************************************************
	**/

	namespace detail {
	template <class>
	constexpr bool is_reference_wrapper_v = false;
	template <class U>
	constexpr bool is_reference_wrapper_v<std::reference_wrapper<U>> = true;
	
	template <class T, class Type, class T1, class... Args>
	constexpr decltype(auto) INVOKE(Type T::* f, T1&& t1, Args&&... args)
	{
		if constexpr (std::is_member_function_pointer_v<decltype(f)>) {
			if constexpr (std::is_base_of_v<T, std::decay_t<T1>>)
				return (gp::forward<T1>(t1).*f)(gp::forward<Args>(args)...);
			else if constexpr (is_reference_wrapper_v<std::decay_t<T1>>)
				return (t1.get().*f)(gp::forward<Args>(args)...);
			else
				return ((*gp::forward<T1>(t1)).*f)(gp::forward<Args>(args)...);
		} else {
			static_assert(std::is_member_object_pointer_v<decltype(f)>);
			static_assert(sizeof...(args) == 0);
			if constexpr (std::is_base_of_v<T, std::decay_t<T1>>)
				return gp::forward<T1>(t1).*f;
			else if constexpr (is_reference_wrapper_v<std::decay_t<T1>>)
				return t1.get().*f;
			else
				return (*gp::forward<T1>(t1)).*f;
		}
	}
	
	template <class F, class... Args>
	constexpr decltype(auto) INVOKE(F&& f, Args&&... args)
	{
		return gp::forward<F>(f)(gp::forward<Args>(args)...);
	}
	} // namespace detail
	
	template< class F, class... Args>
	constexpr std::invoke_result_t<F, Args...> invoke(F&& f, Args&&... args) 
	noexcept(std::is_nothrow_invocable_v<F, Args...>)
	{
		return detail::INVOKE(gp::forward<F>(f), gp::forward<Args>(args)...);
	}

	template< class T >
	T* addressof(T& arg) 
	{
		return reinterpret_cast<T*>(
				&const_cast<char&>(
					reinterpret_cast<const volatile char&>(arg)));
	}

	namespace detail {
	template <class T> constexpr T& FUN(T& t) noexcept { return t; }
	template <class T> void FUN(T&&) = delete;
	}
	
	template <class T>
	class reference_wrapper {
	public:
	// types
	typedef T type;
	
	// construct/copy/destroy
	template <class U, class = decltype(
		detail::FUN<T>(std::declval<U>()),
		std::enable_if_t<!std::is_same_v<reference_wrapper, gp::remove_cvref_t<U>>>()
	)>
	constexpr reference_wrapper(U&& u) noexcept(noexcept(detail::FUN<T>(gp::forward<U>(u))))
		: _ptr(gp::addressof(detail::FUN<T>(gp::forward<U>(u)))) {}
	reference_wrapper(const reference_wrapper&) noexcept = default;
	
	// assignment
	reference_wrapper& operator=(const reference_wrapper& x) noexcept = default;
	
	// access
	constexpr operator T& () const noexcept { return *_ptr; }
	constexpr T& get() const noexcept { return *_ptr; }
	
	template< class... ArgTypes >
	constexpr std::invoke_result_t<T&, ArgTypes...>
		operator() ( ArgTypes&&... args ) const {
		return gp::invoke(get(), gp::forward<ArgTypes>(args)...);
	}
	
	private:
	T* _ptr;
	};
	
	// deduction guides
	template<class T>
	reference_wrapper(T&) -> reference_wrapper<T>;

	template<typename T>
	auto ref(T& vref) {
		return reference_wrapper<T>(vref);
	}

	template <class _DecayFunc>
	class __not_fn_imp {
	_DecayFunc __fd;

	public:
		__not_fn_imp() = delete;

		template <class ..._Args>
		auto operator()(_Args&& ...__args) &
				noexcept(noexcept(!gp::invoke(__fd, gp::forward<_Args>(__args)...)))
			-> decltype(          !gp::invoke(__fd, gp::forward<_Args>(__args)...))
			{ return              !gp::invoke(__fd, gp::forward<_Args>(__args)...); }

		template <class ..._Args>
		auto operator()(_Args&& ...__args) &&
				noexcept(noexcept(!gp::invoke(gp::move(__fd), gp::forward<_Args>(__args)...)))
			-> decltype(          !gp::invoke(gp::move(__fd), gp::forward<_Args>(__args)...))
			{ return              !gp::invoke(gp::move(__fd), gp::forward<_Args>(__args)...); }

		template <class ..._Args>
		auto operator()(_Args&& ...__args) const&
				noexcept(noexcept(!gp::invoke(__fd, gp::forward<_Args>(__args)...)))
			-> decltype(          !gp::invoke(__fd, gp::forward<_Args>(__args)...))
			{ return              !gp::invoke(__fd, gp::forward<_Args>(__args)...); }


		template <class ..._Args>
		auto operator()(_Args&& ...__args) const&&
				noexcept(noexcept(!gp::invoke(gp::move(__fd), gp::forward<_Args>(__args)...)))
			-> decltype(          !gp::invoke(gp::move(__fd), gp::forward<_Args>(__args)...))
			{ return              !gp::invoke(gp::move(__fd), gp::forward<_Args>(__args)...); }

	private:
		template <class _RawFunc,
				class = std::enable_if_t<!std::is_same<std::decay_t<_RawFunc>, __not_fn_imp>::value>>
		explicit __not_fn_imp(_RawFunc&& __rf)
			: __fd(gp::forward<_RawFunc>(__rf)) {}

		template <class _RawFunc>
		friend inline __not_fn_imp<std::decay_t<_RawFunc>> not_fn(_RawFunc&&);
	};

	template <class _RawFunc>
	inline __not_fn_imp<std::decay_t<_RawFunc>> not_fn(_RawFunc&& __fn) {
		return __not_fn_imp<std::decay_t<_RawFunc>>(gp::forward<_RawFunc>(__fn));
	}
	/**
	 *********************************************************************************************
	 */
}