On Jul 12, 2011, at 6:41 AM, Maurizio Giordano wrote:
> Hi Matthias, hi schemers,
>
> 2011/7/11 Matthias Felleisen <matth...@ccs.neu.edu>
>
> Now I don't understand at all why you want to use eval in the macro.
> If the right-hand side just returned the lambda that you have there,
> it would automatically capture the variables in the context of the
> gama rule.
>
>
> Have you tried just returning the lambda as is from the macro?
>
> I tried but it doesn't work! Here you find a sample of what you suggest:
> ---------------
> (define-syntax mymacro
> (syntax-rules (prova)
> [(mymacro input ...)
> (lambda (z) (list input ...) (+ z extern-var))]))
>
> > (let* ((extern-var 2) (f (mymacro x y))) (f 1))
> reference to undefined identifier: extern-var
Here is what I meant:
#lang racket
(define-syntax-rule
(mm x)
(lambda (w) (displayln `(,x)) (+ w x)))
(define f
(let ([a 10])
(mm a)))
(f 42)
More later -- Matthias
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