Re: Injecting variables into closures.

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

On Thu, 29 Nov 2007, Kjetil S. Matheussen wrote:

>
> Hi,
>
> I need (well) to inject variables into closures, and have
> come up with the following macro to do so:
>
> (define-macro (inject-variable name value)
...
>                         (cond ((null? (cdr ,env))
...
>                               ((null? (null? (cdr (car ,env))))


#@^%$^&#!


(define-macro (inject-variable name value)
   (define env (gensym))
   (define closure (gensym))
   (define vars (gensym))
   (define secondname (gensym))
   (define secondval (gensym))
   (define first-env (gensym))
   `((procedure->macro
      (lambda (,(gensym) ,env)
        (define ,first-env (car ,env))
        (cond ((null? (cdr ,env))
 	      (let ((,closure ,first-env))
 		(set-car! ,env (cons ',name ,value))
 		(set-cdr! ,env (list ,closure))))
 	     ((not (pair? (cdr ,first-env)))
 	      (let* ((,vars ,first-env)
 		     (,secondname (car ,vars))
 		     (,secondval (cdr ,vars)))
 		(set-car! ,env
 			  (list (list ',name ,secondname)
 				,value ,secondval))))
 	     (else
 	      (set-cdr! ,first-env
 			(cons ,value (cdr ,first-env)))
 	      (set-car! ,first-env
 			(cons ',name (car ,first-env)))
 	      (set-car! ,env ,first-env)))))))


Sorry. :-)



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