STL/stl/inc/compare

// compare standard header (core)

// Copyright (c) Microsoft Corporation.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#pragma once
#ifndef _COMPARE_
#define _COMPARE_
#include <yvals_core.h>
#if _STL_COMPILER_PREPROCESSOR

#if !_HAS_CXX20
#pragma message("The contents of <compare> are available only with C++20 or later.")
#else // ^^^ !_HAS_CXX20 / _HAS_CXX20 vvv
#include <xtr1common>

#pragma pack(push, _CRT_PACKING)
#pragma warning(push, _STL_WARNING_LEVEL)
#pragma warning(disable : _STL_DISABLED_WARNINGS)
_STL_DISABLE_CLANG_WARNINGS
#pragma push_macro("new")
#undef new

_STD_BEGIN
using _Literal_zero = decltype(nullptr);
using _Compare_t    = signed char;

// These "pretty" enumerator names are safe since they reuse names of user-facing entities.
enum class _Compare_eq : _Compare_t { equal = 0, equivalent = equal, nonequal = 1, nonequivalent = nonequal };
enum class _Compare_ord : _Compare_t { less = -1, greater = 1 };
enum class _Compare_ncmp : _Compare_t { unordered = -127 };

// CLASS weak_equality
class weak_equality {
public:
    _NODISCARD constexpr explicit weak_equality(const _Compare_eq _Value_) noexcept
        : _Value(static_cast<_Compare_t>(_Value_)) {}

    static const weak_equality equivalent;
    static const weak_equality nonequivalent;

    _NODISCARD friend constexpr bool operator==(const weak_equality _Val, _Literal_zero) noexcept {
        return _Val._Value == 0;
    }

#ifdef __cpp_impl_three_way_comparison
    // This declaration additionally requires P1185, but that proposal has no feature-test macro.
    _NODISCARD friend constexpr bool operator==(const weak_equality&, const weak_equality&) noexcept = default;

    _NODISCARD friend constexpr weak_equality operator<=>(const weak_equality _Val, _Literal_zero) noexcept {
        return _Val;
    }

    _NODISCARD friend constexpr weak_equality operator<=>(_Literal_zero, const weak_equality _Val) noexcept {
        return _Val;
    }
#else // ^^^ supports <=> and P1185 / supports neither vvv
    _NODISCARD friend constexpr bool operator!=(const weak_equality _Val, _Literal_zero) noexcept {
        return _Val._Value != 0;
    }

    _NODISCARD friend constexpr bool operator==(_Literal_zero, const weak_equality _Val) noexcept {
        return _Val._Value == 0;
    }

    _NODISCARD friend constexpr bool operator!=(_Literal_zero, const weak_equality _Val) noexcept {
        return _Val._Value != 0;
    }
#endif // __cpp_impl_three_way_comparison

private:
    _Compare_t _Value;
};

inline constexpr weak_equality weak_equality::equivalent(_Compare_eq::equivalent);
inline constexpr weak_equality weak_equality::nonequivalent(_Compare_eq::nonequivalent);

// CLASS strong_equality
class strong_equality {
public:
    _NODISCARD constexpr explicit strong_equality(const _Compare_eq _Value_) noexcept
        : _Value(static_cast<_Compare_t>(_Value_)) {}

    static const strong_equality equal;
    static const strong_equality nonequal;
    static const strong_equality equivalent;
    static const strong_equality nonequivalent;

    constexpr operator weak_equality() const noexcept {
        return weak_equality{static_cast<_Compare_eq>(_Value != 0)};
    }

    _NODISCARD friend constexpr bool operator==(const strong_equality _Val, _Literal_zero) noexcept {
        return _Val._Value == 0;
    }

#ifdef __cpp_impl_three_way_comparison
    // This declaration additionally requires P1185, but that proposal has no feature-test macro.
    _NODISCARD friend constexpr bool operator==(const strong_equality&, const strong_equality&) noexcept = default;

    _NODISCARD friend constexpr strong_equality operator<=>(const strong_equality _Val, _Literal_zero) noexcept {
        return _Val;
    }

    _NODISCARD friend constexpr strong_equality operator<=>(_Literal_zero, const strong_equality _Val) noexcept {
        return _Val;
    }
#else // ^^^ supports <=> and P1185 / supports neither vvv
    _NODISCARD friend constexpr bool operator!=(const strong_equality _Val, _Literal_zero) noexcept {
        return _Val._Value != 0;
    }

    _NODISCARD friend constexpr bool operator==(_Literal_zero, const strong_equality _Val) noexcept {
        return _Val._Value == 0;
    }

    _NODISCARD friend constexpr bool operator!=(_Literal_zero, const strong_equality _Val) noexcept {
        return _Val._Value != 0;
    }
#endif // __cpp_impl_three_way_comparison

private:
    _Compare_t _Value;
};

inline constexpr strong_equality strong_equality::equal(_Compare_eq::equal);
inline constexpr strong_equality strong_equality::nonequal(_Compare_eq::nonequal);
inline constexpr strong_equality strong_equality::equivalent(_Compare_eq::equivalent);
inline constexpr strong_equality strong_equality::nonequivalent(_Compare_eq::nonequivalent);

// CLASS partial_ordering
class partial_ordering {
public:
    _NODISCARD constexpr explicit partial_ordering(const _Compare_eq _Value_) noexcept
        : _Value(static_cast<_Compare_t>(_Value_)), _Is_ordered(true) {}
    _NODISCARD constexpr explicit partial_ordering(const _Compare_ord _Value_) noexcept
        : _Value(static_cast<_Compare_t>(_Value_)), _Is_ordered(true) {}
    _NODISCARD constexpr explicit partial_ordering(const _Compare_ncmp _Value_) noexcept
        : _Value(static_cast<_Compare_t>(_Value_)), _Is_ordered(false) {}

    static const partial_ordering less;
    static const partial_ordering equivalent;
    static const partial_ordering greater;
    static const partial_ordering unordered;

    constexpr operator weak_equality() const noexcept {
        return weak_equality{static_cast<_Compare_eq>(_Value != 0)};
    }

    _NODISCARD friend constexpr bool operator==(const partial_ordering _Val, _Literal_zero) noexcept {
        return _Val._Is_ordered && _Val._Value == 0;
    }

#ifdef __cpp_impl_three_way_comparison
    // This declaration additionally requires P1185, but that proposal has no feature-test macro.
    _NODISCARD friend constexpr bool operator==(const partial_ordering&, const partial_ordering&) noexcept = default;
#else // ^^^ supports <=> and P1185 / supports neither vvv
    _NODISCARD friend constexpr bool operator!=(const partial_ordering _Val, _Literal_zero) noexcept {
        return !_Val._Is_ordered || _Val._Value != 0;
    }

    _NODISCARD friend constexpr bool operator==(_Literal_zero, const partial_ordering _Val) noexcept {
        return _Val._Is_ordered && 0 == _Val._Value;
    }

    _NODISCARD friend constexpr bool operator!=(_Literal_zero, const partial_ordering _Val) noexcept {
        return !_Val._Is_ordered || 0 != _Val._Value;
    }
#endif // __cpp_impl_three_way_comparison

    _NODISCARD friend constexpr bool operator<(const partial_ordering _Val, _Literal_zero) noexcept {
        return _Val._Is_ordered && _Val._Value < 0;
    }

    _NODISCARD friend constexpr bool operator>(const partial_ordering _Val, _Literal_zero) noexcept {
        return _Val._Is_ordered && _Val._Value > 0;
    }

    _NODISCARD friend constexpr bool operator<=(const partial_ordering _Val, _Literal_zero) noexcept {
        return _Val._Is_ordered && _Val._Value <= 0;
    }

    _NODISCARD friend constexpr bool operator>=(const partial_ordering _Val, _Literal_zero) noexcept {
        return _Val._Is_ordered && _Val._Value >= 0;
    }

    _NODISCARD friend constexpr bool operator<(_Literal_zero, const partial_ordering _Val) noexcept {
        return _Val._Is_ordered && 0 < _Val._Value;
    }

    _NODISCARD friend constexpr bool operator>(_Literal_zero, const partial_ordering _Val) noexcept {
        return _Val._Is_ordered && 0 > _Val._Value;
    }

    _NODISCARD friend constexpr bool operator<=(_Literal_zero, const partial_ordering _Val) noexcept {
        return _Val._Is_ordered && 0 <= _Val._Value;
    }

    _NODISCARD friend constexpr bool operator>=(_Literal_zero, const partial_ordering _Val) noexcept {
        return _Val._Is_ordered && 0 >= _Val._Value;
    }

#ifdef __cpp_impl_three_way_comparison
    _NODISCARD friend constexpr partial_ordering operator<=>(const partial_ordering _Val, _Literal_zero) noexcept {
        return _Val;
    }

    _NODISCARD friend constexpr partial_ordering operator<=>(_Literal_zero, const partial_ordering _Val) noexcept {
        return partial_ordering{static_cast<_Compare_ord>(-_Val._Value)};
    }
#endif // __cpp_impl_three_way_comparison

private:
    _Compare_t _Value;
    bool _Is_ordered;
};

inline constexpr partial_ordering partial_ordering::less(_Compare_ord::less);
inline constexpr partial_ordering partial_ordering::equivalent(_Compare_eq::equivalent);
inline constexpr partial_ordering partial_ordering::greater(_Compare_ord::greater);
inline constexpr partial_ordering partial_ordering::unordered(_Compare_ncmp::unordered);

// CLASS weak_ordering
class weak_ordering {
public:
    _NODISCARD constexpr explicit weak_ordering(const _Compare_eq _Value_) noexcept
        : _Value(static_cast<_Compare_t>(_Value_)) {}
    _NODISCARD constexpr explicit weak_ordering(const _Compare_ord _Value_) noexcept
        : _Value(static_cast<_Compare_t>(_Value_)) {}

    static const weak_ordering less;
    static const weak_ordering equivalent;
    static const weak_ordering greater;

    constexpr operator weak_equality() const noexcept {
        return weak_equality{static_cast<_Compare_eq>(_Value != 0)};
    }

    constexpr operator partial_ordering() const noexcept {
        return partial_ordering{static_cast<_Compare_ord>(_Value)};
    }

    _NODISCARD friend constexpr bool operator==(const weak_ordering _Val, _Literal_zero) noexcept {
        return _Val._Value == 0;
    }

#ifdef __cpp_impl_three_way_comparison
    // This declaration additionally requires P1185, but that proposal has no feature-test macro.
    _NODISCARD friend constexpr bool operator==(const weak_ordering&, const weak_ordering&) noexcept = default;
#else // ^^^ supports <=> and P1185 / supports neither vvv
    _NODISCARD friend constexpr bool operator!=(const weak_ordering _Val, _Literal_zero) noexcept {
        return _Val._Value != 0;
    }

    _NODISCARD friend constexpr bool operator==(_Literal_zero, const weak_ordering _Val) noexcept {
        return 0 == _Val._Value;
    }

    _NODISCARD friend constexpr bool operator!=(_Literal_zero, const weak_ordering _Val) noexcept {
        return 0 != _Val._Value;
    }
#endif // __cpp_impl_three_way_comparison

    _NODISCARD friend constexpr bool operator<(const weak_ordering _Val, _Literal_zero) noexcept {
        return _Val._Value < 0;
    }

    _NODISCARD friend constexpr bool operator>(const weak_ordering _Val, _Literal_zero) noexcept {
        return _Val._Value > 0;
    }

    _NODISCARD friend constexpr bool operator<=(const weak_ordering _Val, _Literal_zero) noexcept {
        return _Val._Value <= 0;
    }

    _NODISCARD friend constexpr bool operator>=(const weak_ordering _Val, _Literal_zero) noexcept {
        return _Val._Value >= 0;
    }

    _NODISCARD friend constexpr bool operator<(_Literal_zero, const weak_ordering _Val) noexcept {
        return 0 < _Val._Value;
    }

    _NODISCARD friend constexpr bool operator>(_Literal_zero, const weak_ordering _Val) noexcept {
        return 0 > _Val._Value;
    }

    _NODISCARD friend constexpr bool operator<=(_Literal_zero, const weak_ordering _Val) noexcept {
        return 0 <= _Val._Value;
    }

    _NODISCARD friend constexpr bool operator>=(_Literal_zero, const weak_ordering _Val) noexcept {
        return 0 >= _Val._Value;
    }

#ifdef __cpp_impl_three_way_comparison
    _NODISCARD friend constexpr weak_ordering operator<=>(const weak_ordering _Val, _Literal_zero) noexcept {
        return _Val;
    }

    _NODISCARD friend constexpr weak_ordering operator<=>(_Literal_zero, const weak_ordering _Val) noexcept {
        return weak_ordering{static_cast<_Compare_ord>(-_Val._Value)};
    }
#endif // __cpp_impl_three_way_comparison

private:
    _Compare_t _Value;
};

inline constexpr weak_ordering weak_ordering::less(_Compare_ord::less);
inline constexpr weak_ordering weak_ordering::equivalent(_Compare_eq::equivalent);
inline constexpr weak_ordering weak_ordering::greater(_Compare_ord::greater);

// CLASS strong_ordering
class strong_ordering {
public:
    _NODISCARD constexpr explicit strong_ordering(const _Compare_eq _Value_) noexcept
        : _Value(static_cast<_Compare_t>(_Value_)) {}
    _NODISCARD constexpr explicit strong_ordering(const _Compare_ord _Value_) noexcept
        : _Value(static_cast<_Compare_t>(_Value_)) {}

    static const strong_ordering less;
    static const strong_ordering equal;
    static const strong_ordering equivalent;
    static const strong_ordering greater;

    constexpr operator weak_equality() const noexcept {
        return weak_equality{static_cast<_Compare_eq>(_Value != 0)};
    }

    constexpr operator strong_equality() const noexcept {
        return strong_equality{static_cast<_Compare_eq>(_Value != 0)};
    }

    constexpr operator partial_ordering() const noexcept {
        return partial_ordering{static_cast<_Compare_ord>(_Value)};
    }

    constexpr operator weak_ordering() const noexcept {
        return weak_ordering{static_cast<_Compare_ord>(_Value)};
    }

    _NODISCARD friend constexpr bool operator==(const strong_ordering _Val, _Literal_zero) noexcept {
        return _Val._Value == 0;
    }

#ifdef __cpp_impl_three_way_comparison
    // This declaration additionally requires P1185, but that proposal has no feature-test macro.
    _NODISCARD friend constexpr bool operator==(const strong_ordering&, const strong_ordering&) noexcept = default;
#else // ^^^ supports <=> and P1185 / supports neither vvv
    _NODISCARD friend constexpr bool operator!=(const strong_ordering _Val, _Literal_zero) noexcept {
        return _Val._Value != 0;
    }

    _NODISCARD friend constexpr bool operator==(_Literal_zero, const strong_ordering _Val) noexcept {
        return 0 == _Val._Value;
    }

    _NODISCARD friend constexpr bool operator!=(_Literal_zero, const strong_ordering _Val) noexcept {
        return 0 != _Val._Value;
    }
#endif // __cpp_impl_three_way_comparison

    _NODISCARD friend constexpr bool operator<(const strong_ordering _Val, _Literal_zero) noexcept {
        return _Val._Value < 0;
    }

    _NODISCARD friend constexpr bool operator>(const strong_ordering _Val, _Literal_zero) noexcept {
        return _Val._Value > 0;
    }

    _NODISCARD friend constexpr bool operator<=(const strong_ordering _Val, _Literal_zero) noexcept {
        return _Val._Value <= 0;
    }

    _NODISCARD friend constexpr bool operator>=(const strong_ordering _Val, _Literal_zero) noexcept {
        return _Val._Value >= 0;
    }

    _NODISCARD friend constexpr bool operator<(_Literal_zero, const strong_ordering _Val) noexcept {
        return 0 < _Val._Value;
    }

    _NODISCARD friend constexpr bool operator>(_Literal_zero, const strong_ordering _Val) noexcept {
        return 0 > _Val._Value;
    }

    _NODISCARD friend constexpr bool operator<=(_Literal_zero, const strong_ordering _Val) noexcept {
        return 0 <= _Val._Value;
    }

    _NODISCARD friend constexpr bool operator>=(_Literal_zero, const strong_ordering _Val) noexcept {
        return 0 >= _Val._Value;
    }

#ifdef __cpp_impl_three_way_comparison
    _NODISCARD friend constexpr strong_ordering operator<=>(const strong_ordering _Val, _Literal_zero) noexcept {
        return _Val;
    }

    _NODISCARD friend constexpr strong_ordering operator<=>(_Literal_zero, const strong_ordering _Val) noexcept {
        return strong_ordering{static_cast<_Compare_ord>(-_Val._Value)};
    }
#endif // __cpp_impl_three_way_comparison

private:
    _Compare_t _Value;
};

inline constexpr strong_ordering strong_ordering::less(_Compare_ord::less);
inline constexpr strong_ordering strong_ordering::equal(_Compare_eq::equal);
inline constexpr strong_ordering strong_ordering::equivalent(_Compare_eq::equivalent);
inline constexpr strong_ordering strong_ordering::greater(_Compare_ord::greater);

// FUNCTION is_eq
_NODISCARD constexpr bool is_eq(const weak_equality _Comp) noexcept {
    return _Comp == 0;
}

// FUNCTION is_neq
_NODISCARD constexpr bool is_neq(const weak_equality _Comp) noexcept {
    return _Comp != 0;
}

// FUNCTION is_lt
_NODISCARD constexpr bool is_lt(const partial_ordering _Comp) noexcept {
    return _Comp < 0;
}

// FUNCTION is_lteq
_NODISCARD constexpr bool is_lteq(const partial_ordering _Comp) noexcept {
    return _Comp <= 0;
}

// FUNCTION is_gt
_NODISCARD constexpr bool is_gt(const partial_ordering _Comp) noexcept {
    return _Comp > 0;
}

// FUNCTION is_gteq
_NODISCARD constexpr bool is_gteq(const partial_ordering _Comp) noexcept {
    return _Comp >= 0;
}

// ALIAS TEMPLATE common_comparison_category_t
template <class _Ty>
inline constexpr bool _Is_comparison_category =
    _Is_any_of_v<_Ty, weak_equality, strong_equality, partial_ordering, weak_ordering, strong_ordering>;

template <class... _Types>
struct common_comparison_category {
    static constexpr bool _All_comparison_categories     = (_Is_comparison_category<_Types> && ...);
    static constexpr bool _At_least_one_weak_equality    = _Is_any_of_v<weak_equality, _Types...>;
    static constexpr bool _At_least_one_strong_equality  = _Is_any_of_v<strong_equality, _Types...>;
    static constexpr bool _At_least_one_partial_ordering = _Is_any_of_v<partial_ordering, _Types...>;
    static constexpr bool _At_least_one_weak_ordering    = _Is_any_of_v<weak_ordering, _Types...>;

    static constexpr bool _Bullet_4_2 =
        _At_least_one_weak_equality
        || (_At_least_one_strong_equality && (_At_least_one_partial_ordering || _At_least_one_weak_ordering));

    using type = conditional_t<_All_comparison_categories,
        conditional_t<_Bullet_4_2, weak_equality,
            conditional_t<_At_least_one_strong_equality, strong_equality,
                conditional_t<_At_least_one_partial_ordering, partial_ordering,
                    conditional_t<_At_least_one_weak_ordering, weak_ordering, strong_ordering>>>>,
        void>;
};

template <class... _Types>
using common_comparison_category_t = typename common_comparison_category<_Types...>::type;

// Other components not yet implemented
_STD_END

#pragma pop_macro("new")
_STL_RESTORE_CLANG_WARNINGS
#pragma warning(pop)
#pragma pack(pop)
#endif // _HAS_CXX20

#endif // _STL_COMPILER_PREPROCESSOR
#endif // _COMPARE_