* Modifying a hook while it's being executed
@ 2005-08-08 15:32 PT
2005-08-08 15:42 ` J. David Boyd
[not found] ` <mailman.3028.1123516720.20277.help-gnu-emacs@gnu.org>
0 siblings, 2 replies; 8+ messages in thread
From: PT @ 2005-08-08 15:32 UTC (permalink / raw)
Is it safe? I haven't seen it anywhere stated explicitly.
For example, I add a hook function to pre-command-hook or
post-command-hook which removes itself from the hook when invoked.
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* Re: Modifying a hook while it's being executed
2005-08-08 15:32 Modifying a hook while it's being executed PT
@ 2005-08-08 15:42 ` J. David Boyd
[not found] ` <mailman.3028.1123516720.20277.help-gnu-emacs@gnu.org>
1 sibling, 0 replies; 8+ messages in thread
From: J. David Boyd @ 2005-08-08 15:42 UTC (permalink / raw)
PT <mailshield.gg@mailnull.com> writes:
> Is it safe? I haven't seen it anywhere stated explicitly.
>
> For example, I add a hook function to pre-command-hook or
> post-command-hook which removes itself from the hook when invoked.
>
Does it blow up emacs? If not, then it is probably safe!
Dave
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* Re: Modifying a hook while it's being executed
[not found] ` <mailman.3028.1123516720.20277.help-gnu-emacs@gnu.org>
@ 2005-08-08 18:51 ` rgb
2005-08-08 20:21 ` kcin
0 siblings, 1 reply; 8+ messages in thread
From: rgb @ 2005-08-08 18:51 UTC (permalink / raw)
J. David Boyd wrote:
> PT <mailshield.gg@mailnull.com> writes:
>
> > Is it safe? I haven't seen it anywhere stated explicitly.
> >
> > For example, I add a hook function to pre-command-hook or
> > post-command-hook which removes itself from the hook when invoked.
> >
>
> Does it blow up emacs? If not, then it is probably safe!
At first I thought something similar, but that's not really
a valid way to view the problem. If something else runs a
hook that would normally execute after the one you are removing
there is a potential for other hooks not to run on that command.
Something like that would not likely manifest itself in a
catastrophic way but could cause unusual behaviors that a
conscientious coder would want to avoid.
This line appears in remove-hook.
(setq hook-value (delete function (copy-sequence hook-value)))
It makes me think that a change to the hook's value will not
be visible to the present execution of the run-hooks command.
So I'd say it appears to be perfectly safe.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Modifying a hook while it's being executed
2005-08-08 18:51 ` rgb
@ 2005-08-08 20:21 ` kcin
2005-08-08 20:34 ` Henrik Enberg
[not found] ` <mailman.3053.1123533819.20277.help-gnu-emacs@gnu.org>
0 siblings, 2 replies; 8+ messages in thread
From: kcin @ 2005-08-08 20:21 UTC (permalink / raw)
rgb wrote:
>
> This line appears in remove-hook.
>
> (setq hook-value (delete function (copy-sequence hook-value)))
>
> It makes me think that a change to the hook's value will not
> be visible to the present execution of the run-hooks command.
> So I'd say it appears to be perfectly safe.
Yes, it seems OK. However I wonder why it is not simply
(setq hook-value (remove function hook-value))
remove also returns a copy. Is there a difference?
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Modifying a hook while it's being executed
2005-08-08 20:21 ` kcin
@ 2005-08-08 20:34 ` Henrik Enberg
[not found] ` <mailman.3053.1123533819.20277.help-gnu-emacs@gnu.org>
1 sibling, 0 replies; 8+ messages in thread
From: Henrik Enberg @ 2005-08-08 20:34 UTC (permalink / raw)
Cc: help-gnu-emacs
> From: kcin@mytrashmail.com
> Date: 8 Aug 2005 13:21:13 -0700
>
> rgb wrote:
> >
> > This line appears in remove-hook.
> >
> > (setq hook-value (delete function (copy-sequence hook-value)))
> >
> > It makes me think that a change to the hook's value will not
> > be visible to the present execution of the run-hooks command.
> > So I'd say it appears to be perfectly safe.
>
> Yes, it seems OK. However I wonder why it is not simply
>
> (setq hook-value (remove function hook-value))
>
> remove also returns a copy. Is there a difference?
`remove' is part of the cl library which isn't supposed to be used in
core Emacs.
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* Re: Modifying a hook while it's being executed
[not found] ` <mailman.3053.1123533819.20277.help-gnu-emacs@gnu.org>
@ 2005-08-08 20:55 ` David Kastrup
2005-08-08 21:08 ` Henrik Enberg
[not found] ` <mailman.3058.1123535725.20277.help-gnu-emacs@gnu.org>
0 siblings, 2 replies; 8+ messages in thread
From: David Kastrup @ 2005-08-08 20:55 UTC (permalink / raw)
Henrik Enberg <henrik.enberg@telia.com> writes:
>> From: kcin@mytrashmail.com
>> Date: 8 Aug 2005 13:21:13 -0700
>>
>> rgb wrote:
>> >
>> > This line appears in remove-hook.
>> >
>> > (setq hook-value (delete function (copy-sequence hook-value)))
>> >
>> > It makes me think that a change to the hook's value will not
>> > be visible to the present execution of the run-hooks command.
>> > So I'd say it appears to be perfectly safe.
>>
>> Yes, it seems OK. However I wonder why it is not simply
>>
>> (setq hook-value (remove function hook-value))
>>
>> remove also returns a copy. Is there a difference?
>
> `remove' is part of the cl library which isn't supposed to be used in
> core Emacs.
remove is a compiled Lisp function in `subr'.
(remove ELT SEQ)
Return a copy of SEQ with all occurrences of ELT removed.
SEQ must be a list, vector, or string. The comparison is done with `equal'.
--
David Kastrup, Kriemhildstr. 15, 44793 Bochum
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Modifying a hook while it's being executed
2005-08-08 20:55 ` David Kastrup
@ 2005-08-08 21:08 ` Henrik Enberg
[not found] ` <mailman.3058.1123535725.20277.help-gnu-emacs@gnu.org>
1 sibling, 0 replies; 8+ messages in thread
From: Henrik Enberg @ 2005-08-08 21:08 UTC (permalink / raw)
> From: David Kastrup <dak@gnu.org>
> Date: Mon, 08 Aug 2005 22:55:17 +0200
>
> Henrik Enberg <henrik.enberg@telia.com> writes:
>
> > `remove' is part of the cl library which isn't supposed to be used in
> > core Emacs.
>
> remove is a compiled Lisp function in `subr'.
> (remove ELT SEQ)
>
> Return a copy of SEQ with all occurrences of ELT removed.
> SEQ must be a list, vector, or string. The comparison is done with `equal'.
doh, I must have been passing through a low flying crack cloud when I
wrote my previous message.
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* Re: Modifying a hook while it's being executed
[not found] ` <mailman.3058.1123535725.20277.help-gnu-emacs@gnu.org>
@ 2005-08-08 21:32 ` David Kastrup
0 siblings, 0 replies; 8+ messages in thread
From: David Kastrup @ 2005-08-08 21:32 UTC (permalink / raw)
Henrik Enberg <henrik.enberg@telia.com> writes:
>> From: David Kastrup <dak@gnu.org>
>> Date: Mon, 08 Aug 2005 22:55:17 +0200
>>
>> Henrik Enberg <henrik.enberg@telia.com> writes:
>>
>> > `remove' is part of the cl library which isn't supposed to be used in
>> > core Emacs.
>>
>> remove is a compiled Lisp function in `subr'.
>> (remove ELT SEQ)
>>
>> Return a copy of SEQ with all occurrences of ELT removed.
>> SEQ must be a list, vector, or string. The comparison is done with `equal'.
>
> doh, I must have been passing through a low flying crack cloud when I
> wrote my previous message.
I would not be terribly surprised if cl had its own keyword-rich
variant of remove.
--
David Kastrup, Kriemhildstr. 15, 44793 Bochum
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2005-08-08 15:32 Modifying a hook while it's being executed PT
2005-08-08 15:42 ` J. David Boyd
[not found] ` <mailman.3028.1123516720.20277.help-gnu-emacs@gnu.org>
2005-08-08 18:51 ` rgb
2005-08-08 20:21 ` kcin
2005-08-08 20:34 ` Henrik Enberg
[not found] ` <mailman.3053.1123533819.20277.help-gnu-emacs@gnu.org>
2005-08-08 20:55 ` David Kastrup
2005-08-08 21:08 ` Henrik Enberg
[not found] ` <mailman.3058.1123535725.20277.help-gnu-emacs@gnu.org>
2005-08-08 21:32 ` David Kastrup
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