banan-os/BAN/include/BAN/Traits.h

#pragma once

namespace BAN
{
	
	template<typename T> struct remove_refenrece { using type = T; };
	template<typename T> struct remove_refenrece<T&> { using type =  T; };
	template<typename T> struct remove_refenrece<T&&> { using type = T; };
	template<typename T> using remove_reference_t = typename remove_refenrece<T>::type;

	template<typename T> struct remove_const { using type = T; };
	template<typename T> struct remove_const<const T> { using type = T; };
	template<typename T> using remove_const_t = typename remove_const<T>::type;

	template<typename T> struct remove_volatile { using type = T; };
	template<typename T> struct remove_volatile<volatile T> { using type = T; };
	template<typename T> using remove_volatile_t = typename remove_volatile<T>::type;

	template<typename T> struct remove_cv { using type = remove_volatile_t<remove_const_t<T>>; };
	template<typename T> using remove_cv_t = typename remove_cv<T>::type;

	template<typename T> struct remove_const_and_reference { using type = remove_const_t<remove_reference_t<T>>; };
	template<typename T> using remove_const_and_reference_t = typename remove_const_and_reference<T>::type;

	template<bool B, typename T = void> struct enable_if {};
	template<typename T> struct enable_if<true, T> { using type = T; };
	template<bool B, typename T = void> using enable_if_t = typename enable_if<B, T>::type;

	template<bool B, typename T> struct maybe_const { using type = T; };
	template<typename T> struct maybe_const<true, T> { using type = const T; };
	template<bool B, typename T> using maybe_const_t = typename maybe_const<B, T>::type;

	struct true_type { static constexpr bool value = true; };
	struct false_type { static constexpr bool value = false; };

	template<typename T, typename S>	struct is_same			: false_type {};
	template<typename T>				struct is_same<T, T>	: true_type {};
	template<typename T, typename S> inline constexpr bool is_same_v = is_same<T, S>::value;

	template<typename T> struct is_lvalue_reference		: false_type {};
	template<typename T> struct is_lvalue_reference<T&>	: true_type {};
	template<typename T> inline constexpr bool is_lvalue_reference_v = is_lvalue_reference<T>::value;
	template<typename T> concept lvalue_reference = is_lvalue_reference_v<T>;

	template<typename T> struct is_integral { static constexpr bool value = requires (T t, T* p, void (*f)(T)) { reinterpret_cast<T>(t); f(0); p + t; }; };
	template<typename T> inline constexpr bool is_integral_v = is_integral<T>::value;
	template<typename T> concept integral = is_integral_v<T>;

	template<typename T>	struct is_floating_point				: false_type {};
	template<>				struct is_floating_point<float>			: true_type {};
	template<>				struct is_floating_point<double>		: true_type {};
	template<>				struct is_floating_point<long double>	: true_type {};
	template<typename T> inline constexpr bool is_floating_point_v = is_floating_point<T>::value;
	template<typename T> concept floating_point = is_floating_point_v<T>;

	template<typename T> struct is_pointer						: false_type {};
	template<typename T> struct is_pointer<T*>					: true_type {};
	template<typename T> struct is_pointer<T* const>			: true_type {};
	template<typename T> struct is_pointer<T* volatile>			: true_type {};
	template<typename T> struct is_pointer<T* const volatile>	: true_type {};
	template<typename T> inline constexpr bool is_pointer_v = is_pointer<T>::value;
	template<typename T> concept pointer = is_pointer_v<T>;

	template<typename T> struct is_const			: false_type {};
	template<typename T> struct is_const<const T>	: true_type {};
	template<typename T> inline constexpr bool is_const_v = is_const<T>::value;
	
	template<typename T> struct is_arithmetic { static constexpr bool value = is_integral_v<T> || is_floating_point_v<T>; };
	template<typename T> inline constexpr bool is_arithmetic_v = is_arithmetic<T>::value;

	namespace detail
	{
		template<typename T, bool = is_arithmetic_v<T>> struct is_signed { static constexpr bool value = T(-1) < T(0); };
		template<typename T> struct is_signed<T, false> : false_type {};
	}
	template<typename T> struct is_signed : detail::is_signed<T> {};
	template<typename T> inline constexpr bool is_signed_v = is_signed<T>::value;

	template<typename T> struct less	{ constexpr bool operator()(const T& lhs, const T& rhs) const { return lhs < rhs; } };
	template<typename T> struct equal	{ constexpr bool operator()(const T& lhs, const T& rhs) const { return lhs == rhs; } };
	template<typename T> struct greater	{ constexpr bool operator()(const T& lhs, const T& rhs) const { return lhs > rhs; } };

}