Question

Is there a generic BitArray in .NET? I only found the non-generic one.

Can there be a generic BitArray? (i.e. would it be reasonable?)

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Edit:

Maybe I should have said type-safe not generic.

Basically when you enumerate the type as object, should it not be int or bool? Or one of them provided in another member enumerator?

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Example:

foreach (bool bit in myBitArray)
{

}

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Edit:

I just checked the enumerator of the BitArray class, but everything returns an object except .Current property:

public virtual object Current

Answer 1

No, there isn’t.

I’m not even sure what part of a BitArray would be generic if there were one.

It wouldn’t be hard to create an extension method to take the BitArray and return a bool[] or List<bool> using a for loop on the BitArray. The for loop would not involve boxing since you would be using the BitArray‘s indexer, and the bool[] List<bool> could be enumerated without boxing as well.

Example extension method:

static List<bool> ToList( this BitArray ba ) {
    List<bool> l = new List<bool>(ba.Count);
    for ( int i = 0 ; i < ba.Count ; i++ ) {
        l.Add( ba[ i ] );
    }
    return l;
}

What I found from a quick benchmark (curiosity overcame me) was that foreach (bool b in myBitArray.ToList()) took 75% to 85% of the time that foreach (bool b in myBitArray). That creates the list each time. Creating the list once and iterating over it many times took 20% to 25% of the time that foreach (bool b in myBitArray) took. You could only take advantage of that if you need to iterate over the bool values multiple times and know that they won’t have changed from the time you called myBitArray.ToList().

foreach (bool b in Enumerable.Cast<bool(myBitArray)) took 150% of the time that foreach (bool b in myBitArray) took.

Yet another edit: I’d say that since it is a game, it probably does make sense for you to do whatever it takes to have a very lean iteration with no boxing/unboxing, even if that means writing your own BitArray. You could save time and use Reflector to copy most of study BitArray‘s code since the class is sealed (can’t inherit and add functionality), just in case there are bit-twiddling optimizations to learn from.

Edit: Struck the suggestion to copy code out of Reflector. Some things, like iterators and closures, yield weird generated code that you don’t want to copy directly anyway.