Re: avoid duplicates in history

[Juri Linkov <juri@jurta.org>]

Dan Nicolaescu <dann@ics.uci.edu> writes:
> Miles Bader <miles@lsi.nec.co.jp> writes:
>   > Yes it is, it runs two words together for no reason.  Just use
>   > `history-delete-duplicates'.
>
> How about the default? Should this be turned on by default? 
>
> I even got some suggestions that deleting duplicates should be the
> only way to do it. 
>
> (It would be nice to have a decision about this, so I can write the
> final docs and patch). 

This is a good feature even without turning it on by default.  I think
it should be installed after renaming to history-delete-duplicates and
updating the Emacs manual and NEWS.

Meanwhile, I'd like to propose a related feature.  It would be useful
to be able to delete some old history elements from the history list.
I think a good key binding for this command in the minibuffer is M-k.

Index: lisp/simple.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/simple.el,v
retrieving revision 1.648
diff -u -r1.648 simple.el
--- lisp/simple.el	13 Jun 2004 22:00:17 -0000	1.648
+++ lisp/simple.el	26 Jun 2004 20:16:59 -0000
@@ -1106,6 +1183,24 @@
   (interactive "p")
   (next-complete-history-element (- n)))
 
+(defun delete-history-element ()
+  "Delete the current minibuffer history element from the history.
+After deleting the element the history position is changed either
+to the the previous history element, or to the next history element
+if the deleted element was the last in the history list."
+  (interactive)
+  (cond
+   ((= minibuffer-history-position 1)
+    (set minibuffer-history-variable
+         (cdr (symbol-value minibuffer-history-variable))))
+   ((> minibuffer-history-position 1)
+    (setcdr (nthcdr (- minibuffer-history-position 2)
+                    (symbol-value minibuffer-history-variable))
+            (nthcdr minibuffer-history-position
+                    (symbol-value minibuffer-history-variable)))))
+  (condition-case nil (next-history-element     1) (error nil))
+  (condition-case nil (previous-history-element 1) (error nil)))
+
 ;; For compatibility with the old subr of the same name.
 (defun minibuffer-prompt-width ()
   "Return the display width of the minibuffer prompt.

Index: lisp/bindings.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/bindings.el,v
retrieving revision 1.132
diff -u -r1.132 bindings.el
--- lisp/bindings.el	12 Jun 2004 10:15:11 -0000	1.132
+++ lisp/bindings.el	26 Jun 2004 20:20:37 -0000
@@ -658,7 +658,8 @@
   (define-key map [prior] 'previous-history-element)
   (define-key map [up]    'previous-history-element)
   (define-key map "\es"   'next-matching-history-element)
-  (define-key map "\er"   'previous-matching-history-element))
+  (define-key map "\er"   'previous-matching-history-element)
+  (define-key map "\ek"   'delete-history-element))
 
 (define-key global-map "\C-u" 'universal-argument)
 (let ((i ?0))

-- 
Juri Linkov
http://www.jurta.org/emacs/