MaxElement.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Algo/Impl/RangePointerType.h"
#include "Templates/IdentityFunctor.h"
#include "Templates/Invoke.h"
#include "Templates/Less.h"
#include "Templates/UnrealTemplate.h" // For MoveTemp
 
namespace AlgoImpl
{
    template <typename RangeType, typename ProjectionType, typename PredicateType>
    constexpr typename TRangePointerType<RangeType>::Type MaxElementBy(RangeType& Range, ProjectionType Proj, PredicateType Pred)
    {
        typename TRangePointerType<RangeType>::Type Result = nullptr;
 
        for (auto& Elem : Range)
        {
            if (!Result || Invoke(Pred, Invoke(Proj, *Result), Invoke(Proj, Elem)))
            {
                Result = &Elem;
            }
        }
 
        return Result;
    }
}
 
namespace Algo
{
    template <typename RangeType>
    [[nodiscard]] UE_REWRITE constexpr auto MaxElement(RangeType&& Range)
        -> decltype(AlgoImpl::MaxElementBy(Range, FIdentityFunctor(), TLess<>()))
    {
        return AlgoImpl::MaxElementBy(Range, FIdentityFunctor(), TLess<>());
    }
 
    template <typename RangeType, typename ComparatorType>
    [[nodiscard]] UE_REWRITE auto MaxElement(RangeType&& Range, ComparatorType Comp)
        -> decltype(AlgoImpl::MaxElementBy(Range, FIdentityFunctor(), MoveTemp(Comp)))
    {
        return AlgoImpl::MaxElementBy(Range, FIdentityFunctor(), MoveTemp(Comp));
    }
 
    template <typename RangeType, typename ProjectionType>
    [[nodiscard]] UE_REWRITE auto MaxElementBy(RangeType&& Range, ProjectionType Proj)
        -> decltype(AlgoImpl::MaxElementBy(Range, MoveTemp(Proj), TLess<>()))
    {
        return AlgoImpl::MaxElementBy(Range, MoveTemp(Proj), TLess<>());
    }
 
    template <typename RangeType, typename ProjectionType, typename ComparatorType>
    [[nodiscard]] UE_REWRITE auto MaxElementBy(RangeType&& Range, ProjectionType Proj, ComparatorType Comp)
        -> decltype(AlgoImpl::MaxElementBy(Range, MoveTemp(Proj), MoveTemp(Comp)))
    {
        return AlgoImpl::MaxElementBy(Range, MoveTemp(Proj), MoveTemp(Comp));
    }
}