Re: [Paul Graham <paulgraham@yahoo.com>] Re: What is alightweight language

[John Clements <address@hidden>]

Title: Re: [Paul Graham <paulgraham@yahoo.com>] Re: What is a

At 12:38 PM -0500 12/14/01, John Clements wrote:

>
> At 10:17 AM -0500 12/14/01,
> jmarshall@mak.com wrote:
> > There is no need for the escape
> > continuation.
> >
> > (define (andmap fn list)
> >   (or (and (pair? list)
> >            (fn (car
> > list))
> >            (andmap
> > fn (cdr list)))
> >       (null? list)
> >       (error "Improper
> > list.")))
> >
> > I don't mean this as a nitpick.  I find it extremely rare that I
> > need
> > to use call-with-current-continuation
> > because CPS doesn't cut it.
>
> Well, I agree that I picked a dreadful
> example; no context is built up.  If I understand you correctly,
> you're suggesting either
>
> a) a global CPS rewrite performed by you,
> the author or all your code, or
> b) a local CPS rewrite of the kind that
> you demonstrate above.
>
> If the former, I don't see how you can
> build large systems this way.  If the latter, your uses of
> call/cc have shrunk to being able to escape from a recursive procedure
> which calls only leaf procedures. That is, you don't have the ability
> to 'abort' parts of the evaluation context which you didn't
> create.
>
> john clements

Let me also respond to my own posting to agree with you: as others have said, I find it extremely rare that I need to use call/cc at all, and hence I would have to agree with you that the number of cases in which I need to use call/cc because CPSing doesn't work is small. That is, if the set B is small, it's true that some subset of B is also small.

john