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Yet another patch for ice-9/q.scm


The problem:
~~~~~~~~~~~

guile> (use-modules (ice-9 q))
guile> (define q (make-q))
guile> q
(())
guile> (enq! q 'a)
(a)
guile> q
((a) a)
guile> (deq! q)
a
guile> q
(() a)
guile> (q-empty? q)
#t
guile> (enq! q 'b)
(b)
guile> q
(() b)
guile> (q-empty? q)
#t

That is, once q became empty, it's impossible to add stuff at the end.


The fix:
~~~~~~~

*** /usr/local/share/guile/1.3a/ice-9/q.scm	Fri Apr 24 21:54:50 1998
--- q.scm	Wed Apr 29 18:01:26 1998
***************
*** 111,117 ****
  (define-public (enq! q d)
    (let ((h (cons d '())))
      (if (not (null? (cdr q)))
!        	(set-cdr! (cdr q) h)
  	(set-car! q h))
      (set-cdr! q h)))
  
--- 111,118 ----
  (define-public (enq! q d)
    (let ((h (cons d '())))
      (if (not (null? (cdr q)))
!         (set-cdr! (cdr q) h))
!     (if (null? (car q))
          (set-car! q h))
      (set-cdr! q h)))