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)
(define env (gensym))
(define closure (gensym))
(define vars (gensym))
(define secondname (gensym))
(define secondval (gensym))
(define first-env (gensym))
`((procedure->macro (lambda (,(gensym) ,env)
(cond ((null? (cdr ,env))
(let ((,closure (car ,env)))
(set-car! ,env (cons ',name ,value))
(set-cdr! ,env (list ,closure))))
((null? (null? (cdr (car ,env))))
(let* ((,vars (car ,env))
(,secondname (car vars))
(,secondval (cdr vars)))
(set-car! ,env
(list (list ',name firstname)
,value ,secondval))))
(else
(let ((,first-env (car ,env)))
(set-cdr! ,first-env
(cons ,value (cdr ,first-env)))
(set-car! ,first-env
(cons ',name (car ,first-env)))
(set-car! ,env ,first-env))))))))
(let ()
(display (defined? 'gakk))
(inject-variable gakk 90)
gakk)
=> #f90
Now I wonder, is this safe and portable? Or are there
other and better ways to do this?
Thanks for any answers.
Kjetil.
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