no continuations

Kevin S. Millikin kmillikin at
Tue Dec 30 17:11:36 EST 2003

On Tuesday, December 30, 2003 5:04 PM, Kevin S. Millikin 
[SMTP:kmillikin at] wrote:
> Oh, sure.  I didn't mean to quibble with the idea that continuations
> are computational effects.  Just wanted to point out that (I think)
> you can't macro express mutation with call/cc, unless you've already
> got mutation anyway.


> Yup.  If you do that, you can use d as your setter and c as your
> getter:
> > (define c (make-cell))
> > (define d c)
> > ((d 'set) 9)
> > (c 'get)
> 9
> > ((d 'set) 17)
> > (c 'get)
> 17

It sure looks like the example contradicts the assertion, but I happen 
to know that there is a set! (or some other assignment) in the macro 
expansion of define.  I'm just using call/cc to get at that, rather 
than getting at the one in the expansion of letrec.

Moved to Haskell Cafe.

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