[racket] generator performance

At Tue, 18 Sep 2012 21:05:57 -0400, Eli Barzilay wrote:
> 10 minutes ago, Matthew Flatt wrote:
> > At Tue, 18 Sep 2012 20:46:40 -0400, Eli Barzilay wrote:
> > > A few minutes ago, Matthew Flatt wrote:
> > > > 
> > > > Using `call/cc' for generators is effectively a hint to the run-time
> > > > system that the continuation doesn't need to compose. That hint is
> > > > useful only because of the way that continuations are implemented
> > > > internally.
> > > 
> > > So `call/cc' is faster than one of the delimited ones?
> > >
> > > -- I tought that the main cost would be in the amount of stack saved
> > > which would make delimited ones faster,
> > 
> > There's no such thing as an un-delimited continuation in Racket. A
> > continuation captured with `call/cc' is delimited by a prompt, just
> > like a continuation captured with
> > `call-with-composable-continuation'.
> 
> Yeah -- I mean that `call/cc' usually has more context, so it seems
> that it would be generally more expensive, and that seems wrong--?

Sorry --- I still don't see what you mean.

The original and revised code include a prompt (or `reset') in the same
place relative to the `shift' or `call/cc', so the delimiting prompt
and the size of the delimited continuation is the same in each case.