What does the parameter code of this method mean?

Question

As the title says, TBitArray<> does not have an exact type, so does it mean that this method can accept any such as TBitArray<int32>, TBitArray<float>, ... as parameters?

FORCEINLINE bool HasAll(const TBitArray<>& Other) const
{
    FConstWordIterator ThisIterator(*this);
    FConstWordIterator OtherIterator(Other);

    while (ThisIterator || OtherIterator)
    {
        const uint32 A = ThisIterator ? ThisIterator.GetWord() : 0;
        const uint32 B = OtherIterator ? OtherIterator.GetWord() : 0;
        if ((A & B) != B)
        {
            return false;
        }

        ++ThisIterator;
        ++OtherIterator;
    }

    return true;
}

And what difference with this code

template<class T>
FORCEINLINE bool HasAll(const TBitArray<T>& Other) const

just in case...if you know java generics, this is not like them. — 463035818_is_not_an_ai, Mar 31 '23 at 07:18

273K · Accepted Answer · 2023-03-31T03:07:34.807

5

TBitArray<> is a template class with all default template parameters. If it's TBitArray<int32> or TBitArray<float> depends on the template definition.

Here is its definition:

template<typename Allocator = FDefaultBitArrayAllocator>
class TBitArray;

So, it's neither int32 nor float, it's the default array allocator.

edited Mar 31 '23 at 03:07

answered Mar 31 '23 at 02:49

273K

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If the template parameter expects an allocator, then how would types like `TBitArray` and `TBitArray` even work in the first place? – Remy Lebeau Mar 31 '23 at 02:57
3

@RemyLebeau They cannot work, they are OP assumptions, but not valid. – 273K Mar 31 '23 at 02:58
OK, so now I see from [Unreal's documentation](https://docs.unrealengine.com/5.1/en-US/API/Runtime/Core/Containers/TBitArray/) that `TBitArray` is just a dynamic array of bits, and you can't instantiate a type like `TBitArray` or `TBitArray` in the first place. Got it, thanks – Remy Lebeau Mar 31 '23 at 03:00

score 2 · Answer 2 · answered Mar 31 '23 at 03:04

so does it mean that this method can accept any such as TBitArray<int32>, TBitArray<float>, ... as parameters?

No.

From the definition of the TBitArray class:

template<typename Allocator = FDefaultBitArrayAllocator>
class TBitArray;

You can see that its template argument takes an Allocator type, and defaults to FDefaultBitArrayAllocator. So, TBitArray<> is just shorthand for TBitArray<FDefaultBitArrayAllocator>.

What does the parameter code of this method mean?

2 Answers2