[plt-scheme] ->d Performance

Yes, the -> is fine. And, so is doing the same bounds check in my own
procedure. I was surprised that the ->d was so much slower. I use contracts
regularly and was trying to expand my usage of them.

On Sat, Apr 11, 2009 at 12:46 PM, Robby Findler <robby at eecs.northwestern.edu
> wrote:

> ->d is definitely substantially slower than the other because the
> wrappers are more complex. Are you finding the performance overhead of
> the ordinary -> acceptable?
>
> Robby
>
> On Sat, Apr 11, 2009 at 1:17 PM, Doug Williams
> <m.douglas.williams at gmail.com> wrote:
> > I would like to use ->d to impose a precondition for a function.  For
> > example:
> >
> >  (matrix-ref
> >   (->d ((matrix matrix?)
> >         (i (and/c exact-nonnegative-integer? (</c (matrix-rows matrix))))
> >         (j (and/c exact-nonnegative-integer? (</c (matrix-cols
> matrix)))))
> >        ()
> >        (result any/c)))
> >
> > or
> >
> >  (matrix-ref
> >   (->d ((matrix matrix?)
> >         (i exact-nonnegative-integer?)
> >         (j exact-nonnegative-integer?))
> >        ()
> >        #:pre-cond (and (< i (matrix-rows matrix))
> >                        (< j (matrix-cols matrix)))
> >        (result any/c)))
> >
> > instead of just
> >
> >  (matrix-ref
> >   (-> matrix? exact-nonnegative-integer? exact-nonnegative-integer?
> any/c))
> >
> > The first two do work, but are really, really slow.
> >
> > I like having the bounds check in the contract (as opposed to bounds
> check
> > in the matrix-ref code, but can't accept the performance hit. Any ideas?
> >
> > Doug
> >
> >
> > _________________________________________________
> >  For list-related administrative tasks:
> >  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> >
> >
>
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