[racket] Macro Problem

Hello

I am having a problem with the following macro:

(define-syntax lambda-r
   (syntax-rules ()
     ((_ args exp ...)
      (lambda args
        (call-with-current-continuation
         (lambda (return)
             exp ... ))))))

it's meant to define a lambda-r form, which wraps a lambda in call/cc, 
so I can use a "return-like" operator.

The following is an example of using lambda-r:


(define test-return
   (lambda-r ()
             (let ((input (read)))
               (if (number? input)
                   (if (> input 0)
                       (begin
                         (display "positive")
                         (return input))                        ;; if 
input is > 0 this should escape out of the procedure
                       (display "negative or zero"))
                   (display "not a number"))
               (display "no return")                         ;; if input 
is > 0 this shouldn't get displayed
               )))

I get the following error when I run the previous example (and enter a 
positive integer):

  => reference to undefined identifier: return

The puzzling thing is that if I run the macro expansion (as shown by the 
Macro Stepper), it works !
Here is the macro expansion:

(define test-return
   (lambda ()
     (call-with-current-continuation
      (lambda (return)
        (let ((input (read)))
          (if (number? input)
            (if (> input 0)
              (begin (display "positive") (return input))
              (display "negative or zero"))
            (display "not a number"))
          (display "no return"))))))


What I am missing ?

Thanks

M
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.racket-lang.org/users/archive/attachments/20100709/b148f60f/attachment.html>