Re: [EXPERIMENTAL PATCH] Extending Isearch-repeat-forward/backward to support a prefix argument following suggesion by Juri Linkov

[Gideon Stupp <gideon.stupp@gmail.com>]

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Hi Juri,

I am attaching a short patch which implements prefix arg support for
'isearch-repeat-forward' and 'isearch-repeat-backward'. It does not contain
any visual hints or even hooks for visual support because it seems
worthwhile to test this functionality for a while before adding anything
"fancy" as you say.  Negative arguments are supported in what seems to me a
reasonable way, though clearly not ideal for regex searches as point out.

Please let me know if you think any more changes are required.

Thanks, Gideon.


On Fri, Jan 27, 2012 at 2:07 PM, Juri Linkov <juri@jurta.org> wrote:

> > Thank you for your comments Juri.  Do you have a thought on how to
> > implement this functionality as a package the way Stefan asked for?
>
> Adding a new count argument to `isearch-repeat-forward' is a pretty
> unobtrusive change and is standard Emacs practice.  But if you want
> to do fancy stuff with hint display then you could add a hook to
> `isearch-lazy-highlight-update' and implement fancy features in a separate
> package whose functionality is added by the hook.
>
> > Negative arguments in particular seem to be challenging. Right now I
> > implemented negative argument navigation by calling isearch-repeat with
> the
> > opposite functionality but that has all kinds of odd effects.
> > For example the search message changes, C-- C-1 isearch-forward does
> > not go back one matched string but rather just switches to
> > isearch-backward and so on.
>
> Then you need to take into account this situation and to add 1 to the
> counter when isearch-forward switches to isearch-backward with C-- C-1.
>
> > I did implement visual hints for the negative arguments because that
> > would require changing the way lazy highlight works significantly
> > (lazy-highlight loop wraps around back to the first line and at that
> > point you can't know the negative argument for the current match).
>
> There are other problems with negative arguments: sometimes backward
> regexp search finds more matches than forward regexp search.
> For instance, trying to search a regexp like "a+" forward on a string
> like "aaa" finds all occurrences of "aaa" as one match, but backward
> regexp search matches every "a" individually.
>

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diff --git a/lisp/isearch.el b/lisp/isearch.el
index ce75911..ce12552 100644
--- a/lisp/isearch.el
+++ b/lisp/isearch.el
@@ -1340,15 +1340,37 @@ Use `isearch-exit' to quit without signaling."
   (isearch-push-state)
   (isearch-update))
 
-(defun isearch-repeat-forward ()
+(defun isearch-repeat-forward (&optional arg)
   "Repeat incremental search forwards."
-  (interactive)
-  (isearch-repeat 'forward))
-
-(defun isearch-repeat-backward ()
+  (interactive "p")
+  (if (< arg 0)
+      (progn
+	;; Doesn't do any search, just switches to backward search
+	(isearch-repeat 'backward)
+	(while (< arg 0)
+	  (isearch-repeat 'backward)
+	  (setq arg (1+ arg)))
+	;; Now switch back to forward search
+	(isearch-repeat 'forward))
+    (while (> arg 0)
+      (isearch-repeat 'forward)
+      (setq arg (1- arg)))))
+
+(defun isearch-repeat-backward (&optional arg)
   "Repeat incremental search backwards."
-  (interactive)
-  (isearch-repeat 'backward))
+  (interactive "p")
+  (if (< arg 0)
+      (progn
+	;; Doesn't do any search, just switches to forward search
+	(isearch-repeat 'forward)
+	(while (< arg 0)
+	  (isearch-repeat 'forward)
+	  (setq arg (1+ arg)))
+	;; Now switch back to backward search
+	(isearch-repeat 'backward))
+    (while (> arg 0)
+      (isearch-repeat 'backward)
+      (setq arg (1- arg)))))
 
 (defun isearch-toggle-regexp ()
   "Toggle regexp searching on or off."