20 minutes ago, John Clements wrote:
>
> On Oct 16, 2012, at 7:16 PM, Eli Barzilay wrote:
>
> > So you need to grab it outside of the new tansformer, just like
> > with plain parameters and closures.
>
> just like with plain parameters? that doesn't sound right to me:
>
> #lang racket
>
> (define p (make-parameter 3))
>
> (parameterize ([p (+ 1 (p))])
> (p ))
>
> … produces 4.
>
> That is, the rhs of the parameter-binding is not in the extent of
> the new binding.
>
> Am I misunderstanding you?
Yes -- what I mean is that if you refer to the syntax parameter inside
of a new transformer, then that's equivalent to:
(parameterize ([p (λ () ... (p) ...)])
(p))
and the equivalent of my suggested solution is to make it into
(let ([old-p (p)])
(parameterize ([p (λ () ... (old-p) ...)])
(p)))
--
((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay:
http://barzilay.org/ Maze is Life!
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