Unique.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Templates/UnrealTemplate.h"
#include "Templates/IdentityFunctor.h"
#include "Templates/Invoke.h"
#include "Templates/EqualTo.h"
 
namespace AlgoImpl
{
    template <typename T, typename SizeType, typename ProjectionType, typename BinaryPredicate>
    SizeType Unique(T* Array, SizeType ArraySize, ProjectionType Proj, BinaryPredicate Predicate)
    {
        if (ArraySize <= 1)
        {
            return ArraySize;
        }
 
        T* Result = Array;
        for (T* Iter = Array + 1; Iter != Array + ArraySize; ++Iter)
        {
            if (!Invoke(Predicate, Invoke(Proj, *Result), Invoke(Proj, *Iter))) 
            {
                ++Result;
                if (Result != Iter)
                {
                    *Result = MoveTemp(*Iter);
                }
            }
        }
 
        return static_cast<SizeType>(Result + 1 - Array);
    }
}
 
namespace Algo
{
    template<typename RangeType>
    [[nodiscard]] auto Unique(RangeType&& Range) -> decltype(AlgoImpl::Unique(GetData(Range), GetNum(Range), FIdentityFunctor(), TEqualTo<>{}))
    {
        return AlgoImpl::Unique(GetData(Range), GetNum(Range), FIdentityFunctor(), TEqualTo<>{});
    }
 
    template<typename RangeType, typename BinaryPredicate>
    [[nodiscard]] auto Unique(RangeType&& Range, BinaryPredicate Predicate) -> decltype(AlgoImpl::Unique(GetData(Range), GetNum(Range), FIdentityFunctor(), MoveTemp(Predicate)))
    {
        return AlgoImpl::Unique(GetData(Range), GetNum(Range), FIdentityFunctor(), MoveTemp(Predicate));
    }
 
    template<typename RangeType, typename ProjectionType>
    [[nodiscard]] auto UniqueBy(RangeType&& Range, ProjectionType Proj) -> decltype(AlgoImpl::Unique(GetData(Range), GetNum(Range), MoveTemp(Proj), TEqualTo<>{}))
    {
        return AlgoImpl::Unique(GetData(Range), GetNum(Range), MoveTemp(Proj), TEqualTo<>{});
    }
 
    template<typename RangeType, typename ProjectionType, typename BinaryPredicate>
    [[nodiscard]] auto UniqueBy(RangeType&& Range, ProjectionType Proj, BinaryPredicate Predicate) -> decltype(AlgoImpl::Unique(GetData(Range), GetNum(Range), MoveTemp(Proj), MoveTemp(Predicate)))
    {
        return AlgoImpl::Unique(GetData(Range), GetNum(Range), MoveTemp(Proj), MoveTemp(Predicate));
    }
}