IndexOf.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Templates/IdentityFunctor.h"
#include "Templates/Invoke.h"
#include "Templates/UnrealTemplate.h"
 
namespace AlgoImpl
{
    template <typename RangeType, typename ValueType, typename ProjectionType>
    auto IndexOfBy(RangeType&& Range, const ValueType& Value, ProjectionType Proj)
    {
        auto Num = GetNum(Range);
        auto Data = GetData(Range);
 
        using SizeType = decltype(Num);
        for (SizeType Index = 0; Index < Num; ++Index)
        {
            if (Invoke(Proj, Data[Index]) == Value)
            {
                return Index;
            }
        }
 
        return (SizeType)-1;
    }
 
    template <typename RangeType, typename PredicateType>
    auto IndexOfByPredicate(RangeType&& Range, PredicateType Pred)
    {
        auto Num = GetNum(Range);
        auto Data = GetData(Range);
 
        using SizeType = decltype(Num);
        for (SizeType Index = 0; Index < Num; ++Index)
        {
            if (Invoke(Pred, Data[Index]))
            {
                return Index;
            }
        }
 
        return (SizeType)-1;
    }
}
 
namespace Algo
{
    /**
     * Returns the index of the first element in the range which is equal to the given value.
     *
     * @param  Range  The range to search.
     * @param  Value  The value to search for.
     *
     * @return The index of the first element found, or (SizeType)-1 if none was found (where SizeType = decltype(GetNum(Range)))
     */
    template <typename RangeType, typename ValueType>
    FORCEINLINE auto IndexOf(RangeType&& Range, const ValueType& Value)
    {
        static_assert(TIsContiguousContainer<RangeType>::Value, "Must only be used with contiguous containers");
        return AlgoImpl::IndexOfBy(Forward<RangeType>(Range), Value, FIdentityFunctor());
    }
 
    /**
     * Returns the index of the first element in the range whose projection is equal to the given value.
     *
     * @param  Range  The range to search.
     * @param  Value  The value to search for.
     * @param  Proj   The projection to apply to the element.
     *
     * @return The index of the first element found, or (SizeType)-1 if none was found (where SizeType = decltype(GetNum(Range)))
     */
    template <typename RangeType, typename ValueType, typename ProjectionType>
    FORCEINLINE auto IndexOfBy(RangeType&& Range, const ValueType& Value, ProjectionType Proj)
    {
        static_assert(TIsContiguousContainer<RangeType>::Value, "Must only be used with contiguous containers");
        return AlgoImpl::IndexOfBy(Forward<RangeType>(Range), Value, MoveTemp(Proj));
    }
 
    /**
     * Returns the index of the first element in the range which matches the predicate.
     *
     * @param  Range  The range to search.
     * @param  Pred   The predicate to search for.
     *
     * @return The index of the first element found, or (SizeType)-1 if none was found (where SizeType = decltype(GetNum(Range)))
     */
    template <typename RangeType, typename PredicateType>
    FORCEINLINE auto IndexOfByPredicate(RangeType&& Range, PredicateType Pred)
    {
        static_assert(TIsContiguousContainer<RangeType>::Value, "Must only be used with contiguous containers");
        return AlgoImpl::IndexOfByPredicate(Forward<RangeType>(Range), MoveTemp(Pred));
    }
}