Re: [boost] Sparse Bit Vectors

From: joel de guzman (isis-tech_at_[hidden])
Date: 2001-06-20 21:53:37

----- Original Message -----
From: "David Abrahams" <david.abrahams_at_[hidden]>

>
> ----- Original Message -----
> From: "joel de guzman" <isis-tech_at_[hidden]>
>
> > -> Macintosh style graphical regions. A vector of sparse bit
> >     vectors can represent something like Regions in the Mac.
> >     in fact the Mac-Region inspired this implementation. [  I
> >     am aware that this is patented. I don't know if my
> >      implementation infringes on this patent. But I am also
> >      aware that this patent will expire soon (now)? ]
>
> I think the Mac implementation uses a some kind of difference encoding
from
> row-to-row, so that, e.g., a gray halftone (checkerboard) is actually very
> cheap to encode. If you're not doing that, you probably don't infringe.

Ok. I'm a bit aware that they do some row to row stuff. My implementation
is just a 1D Region (In Mac parlance). Extending that to 2D is straight
forward.
Mac's optimisations seem interesting though. I'd assume that was patented
pre 1983. So that makes the patent open just about now (?).

>
> > -> Compresses bitmaps. Ok, same as above :-)
>
> Or at least bitmasks...

Compressed, drawable and hit-testable as is.

>
> > -> This is interesting... A set of floating point numbers
> >     and ranges. Say we want a set of floating point numbers
> >     from -1 to 1 except 0. You'd write:
> >
> >        fs = range<float>(-1.0,+1.0) - 0.0;
>
> Hmm, we should talk. There is a nearly-finished implementation of
half-open
> ranges in CVS. This work is at least related.

Cool, I'm all ears. My implementation uses closed-ranges. But I guess
it is trivial to use half-open ranges instead.

>
> -Dave
>

Have a nice day, Dave,
Joel de Guzman