> A general solution is non-trivial, as there is a potential risk of memory
> leaks, as associating ordering information with arbitrary lisp objects
> means that we must store a pointer to such objects somewhere, and thus
> may leave references to otherwise unused data.
How 'bout the patch below? Look 'ma, no leak!
Stefan
--- subr.el 14 jun 2005 13:16:55 -0400 1.464
+++ subr.el 14 jun 2005 13:23:20 -0400
@@ -974,25 +974,21 @@
`list-order' property.
The return value is the new value of LIST-VAR."
- (let* ((ordering (get list-var 'list-order))
- (cur (and (symbolp element) (assq element ordering))))
+ (let ((ordering (get list-var 'list-order)))
+ (unless ordering
+ (put list-var 'list-order
+ (setq ordering (make-hash-table :weakness 'key :test 'eq))))
(when order
- (unless (symbolp element)
- (error "cannot specify order for non-symbols"))
- (if cur
- (setcdr cur order)
- (setq cur (cons element order))
- (setq ordering (cons cur ordering))
- (put list-var 'list-order ordering)))
+ (puthash element order ordering))
(add-to-list list-var element)
(set list-var (sort (symbol-value list-var)
(lambda (a b)
- (let ((oa (and (symbolp a) (assq a ordering)))
- (ob (and (symbolp b) (assq b ordering))))
+ (let ((oa (gethash a ordering))
+ (ob (gethash b ordering)))
(cond
((not oa) nil)
((not ob) t)
- (t (< (cdr oa) (cdr ob))))))))))
+ (t (< oa ob)))))))))
;;; Load history
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