[gambit-list] dynamic scope

Marc Feeley feeley at iro.umontreal.ca
Sat Jan 31 20:11:15 EST 2009

On 31-Jan-09, at 7:49 PM, lowly coder wrote:

> is there anyway i can obtain dynamic scoping in gambit? lexically  
> scoping is really cool, and I want it as the default behavior; i  
> just want the ability to go:
> (define (foo x) (* x 2))
> (define (g x) (foo x))
> (pp (list (g 1) (dynamic-let ( (foo (lambda (x) (* x 3)))) (g 1))))
> to get me:
> (2 3)

This is the way you can do dynamic scoping in Gambit (and other  
Schemes too):

(define foo (make-parameter (lambda (x) (* x 2))))

(define (g x) ((foo) x))

(pp (list (g 1) (parameterize ((foo (lambda (x) (* x 3)))) (g 1))))

You can also use dynamic-wind to simulate dynamic scoping but it does  
not work properly with threads.


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