* Behaviour for save-excursion
@ 2009-10-06 13:44 Nathaniel Flath
2009-10-06 14:44 ` martin rudalics
2009-10-06 14:48 ` Chong Yidong
0 siblings, 2 replies; 3+ messages in thread
From: Nathaniel Flath @ 2009-10-06 13:44 UTC (permalink / raw
To: emacs-devel
[-- Attachment #1: Type: text/plain, Size: 749 bytes --]
What is the proper behaviour for save-excursion? The emacs-lisp intro and
the docstring seem to have slightly differing explanations - namely, the
docstring mentions that it saves current-buffer as well as point and mark,
and the emacs-lisp intro does not. Based on just what it does, I'm not
entirely sure which is correct - the following code snippet, executed in
*scratch*, returns the "*scratch*" buffer but the buffer displayed is the
"bar" buffer, and evaluating current-bufer afterwards returns the "bar"
buffer.
(progn
(save-excursion
(switch-to-buffer "bar"))
(current-buffer))
Either the manual or the docstring should be changed to reflect what it
does, but I'm not entirely sure which based on this.
Thanks,
Nathaniel Flath
[-- Attachment #2: Type: text/html, Size: 838 bytes --]
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Behaviour for save-excursion
2009-10-06 13:44 Behaviour for save-excursion Nathaniel Flath
@ 2009-10-06 14:44 ` martin rudalics
2009-10-06 14:48 ` Chong Yidong
1 sibling, 0 replies; 3+ messages in thread
From: martin rudalics @ 2009-10-06 14:44 UTC (permalink / raw
To: Nathaniel Flath; +Cc: emacs-devel
> What is the proper behaviour for save-excursion? The emacs-lisp intro and
> the docstring seem to have slightly differing explanations - namely, the
> docstring mentions that it saves current-buffer as well as point and mark,
> and the emacs-lisp intro does not. Based on just what it does, I'm not
> entirely sure which is correct - the following code snippet, executed in
> *scratch*, returns the "*scratch*" buffer but the buffer displayed is the
> "bar" buffer, and evaluating current-bufer afterwards returns the "bar"
> buffer.
>
> (progn
> (save-excursion
> (switch-to-buffer "bar"))
> (current-buffer))
>
> Either the manual or the docstring should be changed to reflect what it
> does, but I'm not entirely sure which based on this.
Please read the Elisp manual entry on `save-excursion' which states:
Likewise, `save-excursion' does not restore window-buffer
correspondences altered by functions such as `switch-to-buffer'.
One way to restore these correspondences, and the selected window,
is to use `save-window-excursion' inside `save-excursion' (*note
Window Configurations::).
Also the following entry from section 27.2 The Current Buffer of the
Elisp manual might provide further explanation:
When an editing command returns to the editor command loop, the
command loop designates the buffer displayed in the selected window as
current, to prevent confusion: the buffer that the cursor is in when
Emacs reads a command is the buffer that the command will apply to.
(*Note Command Loop::.) Therefore, `set-buffer' is not the way to
switch visibly to a different buffer so that the user can edit it. For
that, you must use the functions described in *Note Displaying
Buffers::.
martin
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Behaviour for save-excursion
2009-10-06 13:44 Behaviour for save-excursion Nathaniel Flath
2009-10-06 14:44 ` martin rudalics
@ 2009-10-06 14:48 ` Chong Yidong
1 sibling, 0 replies; 3+ messages in thread
From: Chong Yidong @ 2009-10-06 14:48 UTC (permalink / raw
To: Nathaniel Flath; +Cc: emacs-devel
Nathaniel Flath <flat0103@gmail.com> writes:
> What is the proper behaviour for save-excursion? The emacs-lisp intro
> and the docstring seem to have slightly differing explanations -
> namely, the docstring mentions that it saves current-buffer as well as
> point and mark, and the emacs-lisp intro does not.
The Lisp intro does say that it saves current-buffer:
In addition to recording the values of point and mark,
`save-excursion' keeps track of the current buffer, and restores it,
too.
> Based on just what it does, I'm not entirely sure which is correct -
> the following code snippet, executed in *scratch*, returns the
> "*scratch*" buffer but the buffer displayed is the "bar" buffer, and
> evaluating current-bufer afterwards returns the "bar" buffer.
You shouldn't use switch-to-buffer in Lisp code unless you know what
you're doing. That's why the docstring for switch-to-buffer has this:
WARNING: This is NOT the way to work on another buffer temporarily
within a Lisp program! Use `set-buffer' instead. That avoids
messing with the window-buffer correspondences.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2009-10-06 14:48 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2009-10-06 13:44 Behaviour for save-excursion Nathaniel Flath
2009-10-06 14:44 ` martin rudalics
2009-10-06 14:48 ` Chong Yidong
Code repositories for project(s) associated with this external index
https://git.savannah.gnu.org/cgit/emacs.git
https://git.savannah.gnu.org/cgit/emacs/org-mode.git
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.