Re: Closure?

["Kjetil S. Matheussen" <k.s.matheussen@notam02.no>]

Ludovic Court?s:
> "Maciek Godek" <pstrychuj@gmail.com> writes:
>
>> I've been wondering if there's any way to recall
>> (or get inside) an environment of a closure (= to
>> directly access variables bound to a closure)
>
> Yes, with `the-environment':
>
>  guile> ((lambda (a b) (the-environment)) 2 3)
>  (((a b) 2 3) #<eval-closure b7c6dcf8>)
>
> But don't do that, since the representation of environments could
> eventually change.
>

Please don't change it. :-)
It's one of those things which makes Guile special.



Maciek Godek:
>
> Don't worry, I won't :)
> Now I only know how to obtain environment of a closure,
> but I still don't know how to get inside and modify it (I'm
> lacking this `with' I wrote about).
>

The function "local-eval" is probably what you want.

I use local-eval a lot, it's one of the really really
nice features provided by Guile:


(define-macro (with env . code)
   `(local-eval (quote (begin ,@code)) ,env))


(define ++
   (let ((c 0))
     (c-display "env" (the-environment))
     (lambda()
       (set! c (1+ c)) c)))

(++)
=> 1
(with (procedure-environment ++) (set! c 20))

(++)
=> 20