type/type.hpp

#pragma once

// Fix for limits.h not exposing LLONG_MIN, LLONG_MIN, and ULLONG_MAX to C++ context
#ifdef __cplusplus
#define __STDC_VERSION__ 201112L
#endif

#include <float.h>
#include <limits.h>
#include <stddef.h>

namespace type {

// <type_traits>

// clang-format off
template <typename T> struct remove_reference { using type = T; };
template <typename T> struct remove_reference<T &> { using type = T; };
template <typename T> struct remove_reference<T &&> { using type = T; };
template <typename T> using remove_reference_t = typename remove_reference<T>::type;

namespace detail {

	template <typename T> struct type_identity { using type = T; };

	template <typename T> auto try_add_pointer(int) -> type_identity<remove_reference_t<T> *>;
	template <typename T> auto try_add_pointer(...) -> type_identity<T>;

} // namespace detail

template <typename T, T v>
struct integral_constant {
	static constexpr T value = v;
	using value_type = T;
	using type = integral_constant; // using injected-class-name
	constexpr operator value_type() const noexcept { return value; }
	constexpr value_type operator()() const noexcept { return value; } // since c++14
};
template <bool B> using bool_constant = integral_constant<bool, B>;
using false_type = bool_constant<false>;
using true_type = bool_constant<true>;

template <bool B, typename T, typename F> struct conditional { using type = T; };
template <typename T, typename F> struct conditional<false, T, F> { using type = F; };
template <bool B, class T, class F> using conditional_t = typename conditional<B, T, F>::type;

template <typename T> struct is_array : false_type {};
template <typename T> struct is_array<T[]> : true_type {};
template <typename T, size_t N> struct is_array<T[N]> : true_type {};
template <typename T> inline constexpr bool is_array_v = is_array<T>::value;

template <typename T> struct remove_extent { using type = T; };
template <typename T> struct remove_extent<T[]> { using type = T; };
template <typename T, size_t N> struct remove_extent<T[N]> { using type = T; };
template <typename T> using remove_extent_t = typename remove_extent<T>::type;

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_reference : false_type {};
template <typename T> struct is_reference<T &> : true_type {};
template <typename T> struct is_reference<T &&> : true_type {};
template <typename T> inline constexpr bool is_reference_v = is_reference<T>::value;

template <typename T> struct is_function : integral_constant<bool, !is_const_v<const T> && !is_reference_v<T>> {};
template <typename T> inline constexpr bool is_function_v = is_function<T>::value;

template <typename T> struct add_pointer : decltype(detail::try_add_pointer<T>(0)) {};
template <typename T> using add_pointer_t = typename add_pointer<T>::type;

template <typename T> struct remove_cv { using type = T; };
template <typename T> struct remove_cv<const T> { using type = T; };
template <typename T> struct remove_cv<volatile T> { using type = T; };
template <typename T> struct remove_cv<const volatile T> { using type = T; };
template <typename T> struct remove_const { using type = T; };
template <typename T> struct remove_const<const T> { using type = T; };
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_cv_t = typename remove_cv<T>::type;
template <typename T> using remove_const_t = typename remove_const<T>::type;
template <typename T> using remove_volatile_t = typename remove_volatile<T>::type;

template <typename T>
struct decay {
private:
	using U = remove_reference_t<T>;
public:
	using type = conditional_t<is_array_v<U>,
		remove_extent_t<U> *,
		conditional_t<is_function<U>::value,
			add_pointer_t<U>,
			remove_cv_t<U>
		>
	>;
};
template <typename T> using decay_t = typename decay<T>::type;

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

template <typename T>
struct is_floating_point : integral_constant<bool,
	is_same_v<float, remove_cv_t<T>> ||
	is_same_v<double, remove_cv_t<T>> ||
	is_same_v<long double, remove_cv_t<T>>>
{};
template <typename T> inline constexpr auto is_floating_point_v = is_floating_point<T>::value;

template <typename T>
struct is_integral : integral_constant<bool,
	is_same_v<bool, remove_cv_t<T>> ||
	is_same_v<char, remove_cv_t<T>> ||
	is_same_v<signed char, remove_cv_t<T>> ||
	is_same_v<unsigned char, remove_cv_t<T>> ||
	is_same_v<wchar_t, remove_cv_t<T>> ||
	is_same_v<char16_t, remove_cv_t<T>> ||
	is_same_v<char32_t, remove_cv_t<T>> ||
	is_same_v<short int, remove_cv_t<T>> ||
	is_same_v<unsigned short int, remove_cv_t<T>> ||
	is_same_v<int, remove_cv_t<T>> ||
	is_same_v<unsigned int, remove_cv_t<T>> ||
	is_same_v<long int, remove_cv_t<T>> ||
	is_same_v<unsigned long int, remove_cv_t<T>> ||
	is_same_v<long long int, remove_cv_t<T>> ||
	is_same_v<unsigned long long int, remove_cv_t<T>>>
{};
template <typename T> inline constexpr auto is_integral_v = is_integral<T>::value;

// Not part of <type_traits>, but very useful
template <typename...> struct always_false : false_type {};
template <typename... Ts> inline constexpr auto always_false_v = always_false<Ts...>::value;

// <limits>

template <typename T> struct numeric_limits {};

template <>
struct numeric_limits<bool> {
	static constexpr bool min() { return false; }
	static constexpr bool max() { return true; }
};

template <>
struct numeric_limits<char> {
	static constexpr char min() { return CHAR_MIN; }
	static constexpr char max() { return CHAR_MAX; }
};

template <>
struct numeric_limits<signed char> {
	static constexpr signed char min() { return SCHAR_MIN; }
	static constexpr signed char max() { return SCHAR_MAX; }
};

template <>
struct numeric_limits<unsigned char> {
	static constexpr unsigned char min() { return 0; }
	static constexpr unsigned char max() { return UCHAR_MAX; }
};

template <>
struct numeric_limits<short> {
	static constexpr short min() { return SHRT_MIN; }
	static constexpr short max() { return SHRT_MAX; }
};

template <>
struct numeric_limits<int> {
	static constexpr int min() { return INT_MIN; }
	static constexpr int max() { return INT_MAX; }
};

template <>
struct numeric_limits<long> {
	static constexpr long int min() { return LONG_MIN; }
	static constexpr long int max() { return LONG_MAX; }
};

template <>
struct numeric_limits<long long int> {
	static constexpr long long int min() { return LLONG_MIN; }
	static constexpr long long int max() { return LLONG_MAX; }
};

template <>
struct numeric_limits<unsigned short> {
	static constexpr unsigned short min() { return 0; }
	static constexpr unsigned short max() { return USHRT_MAX; }
};

template <>
struct numeric_limits<unsigned int> {
	static constexpr unsigned int min() { return 0; }
	static constexpr unsigned int max() { return UINT_MAX; }
};

template <>
struct numeric_limits<unsigned long int> {
	static constexpr unsigned long int min() { return 0; }
	static constexpr unsigned long int max() { return ULONG_MAX; }
};

template <>
struct numeric_limits<unsigned long long int> {
	static constexpr unsigned long long int min() { return 0; }
	static constexpr unsigned long long int max() { return ULLONG_MAX; }
};

template <>
struct numeric_limits<float> {
	static constexpr float min() { return FLT_MIN; }
	static constexpr float max() { return FLT_MAX; }
	static constexpr float lowest() { return -FLT_MAX; }
};

template <>
struct numeric_limits<double> {
	static constexpr double min() { return DBL_MIN; }
	static constexpr double max() { return DBL_MAX; }
	static constexpr double lowest() { return -DBL_MAX; }
};

template <>
struct numeric_limits<long double> {
	static constexpr long double min() { return LDBL_MIN; }
	static constexpr long double max() { return LDBL_MAX; }
	static constexpr long double lowest() { return -LDBL_MAX; }
};
// clang-format on

} // namespace type