Scoping bug in Racket v5.1.1?

Somebody please tell me this is a bug in Racket (v5.1.1),

It seams to be a scoping problem.

(see code and output below)

The return from example-1 shows that x is not getting incremented as it should and as it does in example-2 and example-3.

The function example-2 is just a copy of example-1 with the reverse instruction removed from doit.

The function example-3 (as you can see) is a copy as well but has an additional parameter which by itself does not change anything but when I test it's value in the cond statement it shows x as being incremented.

In addition if I don't return anything from example-1 but rather print what it now returns it shows x as being incremented.

(define (example-1 lst)
  (letrec([x       0]
          [doit    (lambda ()
                     (reverse 
                      (foldl  
                       (lambda (v store)
                         (set! x (add1 x))
                         (cons v store))
                       '()  
                       lst)))])

    (let*([results   (doit)])
      (list x results)
      )))

(define (example-2 lst)
  (letrec([x       0]
          [doit    (lambda ()
                     (foldl  
                      (lambda (v store)
                        (set! x (add1 x))
                        (cons v store))
                      '()  
                      lst))])

    (let*([res开发者_如何学JAVAults   (doit)])
      (list x results))))

(define (example-3 lst id)
  (letrec([x       0]
          [doit    (lambda ()
                     (reverse 
                      (foldl  
                       (lambda (v store)
                         (set! x (add1 x))
                         (cons v store))
                       '()  
                       lst)))])

    (let*([results   (doit)])
      (cond   [(= 1 id)  'junk])
      (list x results)
      )))

(printf "example-1 : ~a~n"  (example-1 '(a b c)))
(printf "example-2 : ~a~n"  (example-2 '(a b c)))
(printf "example-3 : ~a~n"  (example-3 '(a b c) 1))

output:

example-1 : (0 (a b c))
example-2 : (3 (c b a))
example-3 : (3 (a b c))

It's a bug -- I filed it with a simpler version of your code. (It's unrelated to the jit though.)

Edit: the bug is fixed now.