[Bese-devel] CPS + loop

[ml13 at onlinehome.de]

Hi,

I was toying around with simple choose and fail, which was basically  
working fine, but when I introduced loop, things broke...
I'd be happy about any comments on the code snippet below,  
specifically I am wondering, whether this loop thing is to be  
considered a bug of the CPS transformer or a problem in my code.

Cheers,
	Kilian Sprotte


(setq *call/cc-returns* t)
;; => T

(defvar ks nil "continuation stack")
;; => KS

(defun/cc choose123 ()
   (block nil
     (let/cc k (push k ks) (return 1))
     (let/cc k (push k ks) (return 2))
     3))
;; => CHOOSE123

(defun/cc fail ()
   (if ks
       (kall (pop ks))
       :fail))
;; => FAIL

(defun next ()
   (with-call/cc (fail)))
;; => NEXT

(with-call/cc
   (setq ks nil)
   (let ((l (list (choose123) (choose123) (choose123))))
     (if (not (= 4 (apply #'+ l)))
	(fail)
	l)))
;; => (1 1 2)

(next)
;; => (1 2 1)

(next)
;; => (2 1 1)

(next)
;; => :FAIL

;; so far so good...
;; let's try with loop
(with-call/cc
   (setq ks nil)
   (let ((l (loop repeat 3 collect (choose123))))
     (if (not (= 4 (apply #'+ l)))
	(fail)
	l)))
;; => (1 1 2)

(next)
;; => (1 3)

(next)
;; => :FAIL