(add-to-ordered-list): Rework to use list-order property of list-var.

diff --git a/lisp/subr.el b/lisp/subr.el
index fb48e578157c5629af6724f969b5e2015475b9cb..b67fc14a010e98a1930eb5d01848e0e0b80a3d30 100644 (file)
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -963,25 +963,36 @@ other hooks, such as major mode hooks, can do the job."
 The test for presence of ELEMENT is done with `equal'.
 
 The resulting list is reordered so that the elements are in the
-order given by each element's `list-order' property (a number).
-Elements which are not symbols, and symbol elements without a
-numeric `lisp-order' property are placed at the end of the list.
+order given by each element's numeric list order.  Elements which
+are not symbols, and symbol elements without a numeric list order
+are placed at the end of the list.
 
 If the third optional argument ORDER is non-nil and ELEMENT is
-a symbol, set the symbol's `list-order' property to the given value.
+a symbol, set the symbol's list order to the given value.
+
+The list order for each symbol is stored in LIST-VAR's
+`list-order' property.
 
 The return value is the new value of LIST-VAR."
-  (when (and order (symbolp element))
-    (put element 'list-order (and (numberp order) order)))
-  (add-to-list list-var element)
-  (set list-var (sort (symbol-value list-var)
-                     (lambda (a b)
-                       (let ((oa (and (symbolp a) (get a 'list-order)))
-                             (ob (and (symbolp b) (get b 'list-order))))
-                         (cond
-                          ((not oa) nil)
-                          ((not ob) t)
-                          (t (< oa ob))))))))
+  (let* ((ordering (get list-var 'list-order))
+        (cur (and (symbolp element) (assq element ordering))))
+    (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)))
+    (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))))
+                           (cond
+                            ((not oa) nil)
+                            ((not ob) t)
+                            (t (< (cdr oa) (cdr ob))))))))))
 
 \f
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