Fast 2D matrix of bits

[bearophile]

Timon Gehr:

> The implementation uses int and uint everywhere. I think it is not 64 
> bit aware?

I have not even tried it on a 64 bit system.


>  > // sizex_, sizey_ are signed to catch negative arguments bugs.
> 
> There would be no negative arguments if they were unsigned.

For me a huge unsigned value that I can't catch in the ctor precondition is worse than a negative value that I am able to catch. I don't need to create a 2D matrix with sides bigger than int.max.
I agree that all the other methods are probably better with size_t arguments. I'll fix it.


> Why is it slower?

Ask it to LDC1 developers :-)
Adding that method is easy, if you want it. And I agree it's handy, with syntax mat[x,y] = true/false.
But note the preferred methods to use this matrix are set/reset, because they are faster than the assign. I'll think about it.


> But the signedness of index makes some 
> straightforward optimizations very hard to carry out for the compiler. 
> [...] but it has to emit something more to cope with (im)possible negative values)

Right, index needs to be uint or size_t. I'll fix it.

Thank you for your suggestions and notes,
bye,
bearophile