Redcraft/Redcraft.Utility/Source/Public/Miscellaneous/Compare.h

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#pragma once
#include "CoreTypes.h"
#include "Templates/Utility.h"
#include "TypeTraits/TypeTraits.h"
#include <compare>
NAMESPACE_REDCRAFT_BEGIN
NAMESPACE_MODULE_BEGIN(Redcraft)
NAMESPACE_MODULE_BEGIN(Utility)
// The result of the three-way comparison operator is the built-in type of the compiler, which is directly introduced here
typedef NAMESPACE_STD::partial_ordering partial_ordering;
typedef NAMESPACE_STD::weak_ordering weak_ordering;
typedef NAMESPACE_STD::strong_ordering strong_ordering;
NAMESPACE_PRIVATE_BEGIN
template<int32> struct TCommonComparisonCategoryBasic { };
template<> struct TCommonComparisonCategoryBasic<0> { using Type = strong_ordering; };
template<> struct TCommonComparisonCategoryBasic<2> { using Type = partial_ordering; };
template<> struct TCommonComparisonCategoryBasic<4> { using Type = weak_ordering; };
template<> struct TCommonComparisonCategoryBasic<6> { using Type = partial_ordering; };
template <typename... Types>
struct TCommonComparisonCategoryImpl
: TCommonComparisonCategoryBasic <(0u | ... |
(
CSameAs<Types, strong_ordering > ? 0u :
CSameAs<Types, weak_ordering > ? 4u :
CSameAs<Types, partial_ordering> ? 2u : 1u
)
)>
{ };
NAMESPACE_PRIVATE_END
template <typename... Types>
using TCommonComparisonCategory = typename NAMESPACE_PRIVATE::TCommonComparisonCategoryImpl<Types...>::Type;
template <typename T, typename OrderingType>
concept CThreeWayComparesAs = CSameAs<TCommonComparisonCategory<T, OrderingType>, OrderingType>;
template <typename T, typename U = T, typename OrderingType = partial_ordering>
concept CThreeWayComparable = CWeaklyEqualityComparable<T, U> && CPartiallyOrdered<T, U>
&& CCommonReference<const TRemoveReference<T>&, const TRemoveReference<U>&>
&& requires(const TRemoveReference<T>& A, const TRemoveReference<U>& B,
const TRemoveReference<TCommonReference<const TRemoveReference<T>&, const TRemoveReference<U>&>>& C)
{
{ A <=> A } -> CThreeWayComparesAs<OrderingType>;
{ B <=> B } -> CThreeWayComparesAs<OrderingType>;
{ A <=> B } -> CThreeWayComparesAs<OrderingType>;
{ B <=> A } -> CThreeWayComparesAs<OrderingType>;
{ C <=> C } -> CThreeWayComparesAs<OrderingType>;
};
template <typename T, typename U = T> requires CThreeWayComparable<T, U>
using TCompareThreeWayResult = decltype(DeclVal<const TRemoveReference<T>&>() <=> DeclVal<const TRemoveReference<U>&>());
template <typename T, typename U = T, typename OrderingType = partial_ordering>
concept CSynthThreeWayComparable = CThreeWayComparable<T, U> || CTotallyOrdered<T, U>;
template <typename T, typename U = T> requires CSynthThreeWayComparable<T, U>
constexpr decltype(auto) SynthThreeWayCompare(T&& LHS, U&& RHS)
{
if constexpr (CThreeWayComparable<T, U>)
{
return Forward<T>(LHS) <=> Forward<U>(RHS);
}
else
{
return Forward<T>(LHS) < Forward<U>(RHS) ? weak_ordering::less : Forward<U>(RHS) < Forward<T>(LHS) ? weak_ordering::greater : weak_ordering::equivalent;
}
}
template <typename T, typename U = T> requires CSynthThreeWayComparable<T, U>
using TSynthThreeWayResult = decltype(SynthThreeWayCompare(DeclVal<const TRemoveReference<T>&>(), DeclVal<const TRemoveReference<U>&>()));
NAMESPACE_MODULE_END(Utility)
NAMESPACE_MODULE_END(Redcraft)
NAMESPACE_REDCRAFT_END