[bug #30070] multiple returns from map

[Szavai Gyula]

URL:
  <http://savannah.gnu.org/bugs/?30070>

                 Summary: multiple returns from map
                 Project: Guile
            Submitted by: szgyg
            Submitted on: Mon 07 Jun 2010 06:23:03 PM GMT
                Category: None
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:

; R6RS 11.9:
; "If multiple returns occur from map, the values returned by
; earlier returns are not mutated."

(display "\nGuile's broken map\n")

(define k #f)
(define result #f)
(define results '())
(set! result (map (lambda (x)
                    (if x x (call/cc (lambda (c)
                                       (set! k c)
                                       1))))
                  '(#t #f)))
(set! results (cons result results))
(write results)
(newline)
(if (< (cadr result) 5)
    (k (+ 1 (cadr result))))
(newline)

;;;;;;;;;;;

(display "Correct map implementation\n") ; regarding call/cc.

(define (map f xs)                  ; it isn't tail-recursive
  (if (null? xs) '() (cons (f (car xs)) (map f (cdr xs)))))

(define k #f)
(define result #f)
(define results '())
(set! result (map (lambda (x)
                    (if x x (call/cc (lambda (c)
                                       (set! k c)
                                       1))))
                  '(#t #f)))
(set! results (cons result results))
(write results)
(newline)
(if (< (cadr result) 5)
    (k (+ 1 (cadr result))))
(newline)





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