GNU bug report logs - #38205
Unhelpful documentation for add-variable-watcher.

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Alan Mackenzie <acm <at> muc.de>
Subject: bug#38205: closed (Re: bug#38205: Unhelpful documentation for
 add-variable-watcher.)
Date: Fri, 15 Nov 2019 09:22:02 +0000

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Your bug report

#38205: Unhelpful documentation for add-variable-watcher.

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 38205 <at> debbugs.gnu.org.

-- 
38205: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=38205
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Alan Mackenzie <acm <at> muc.de>
Cc: 38205-done <at> debbugs.gnu.org
Subject: Re: bug#38205: Unhelpful documentation for add-variable-watcher.
Date: Fri, 15 Nov 2019 11:21:29 +0200

> Date: Thu, 14 Nov 2019 07:38:35 +0000
> From: Alan Mackenzie <acm <at> muc.de>
> 
> The doc string for add-variable-watcher wrongly states:
> 
>     Cause WATCH-FUNCTION to be called when SYMBOL is set.
> 
> .  Correct would be either
> 
>     Cause WATCH-FUNCTION to be called just before SYMBOL is set.
> 
> or
> 
>     Cause WATCH-FUNCTION to be called just after SYMBOL is set.

Well, the doc string goes on to say

  NEWVAL is the value it will be changed to.
                         ^^^^^^^
which is a clear hint to what actually happens.  But I made this even
more clear in the doc string, thanks.

> The documentation in the Elisp manual is similarly ambiguous.  It uses
> the conjunction "whenever".

Fixed that as well.

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From: Alan Mackenzie <acm <at> muc.de>
To: bug-gnu-emacs <at> gnu.org
Subject: Unhelpful documentation for add-variable-watcher.
Date: Thu, 14 Nov 2019 07:38:35 +0000

Hello, Emacs.

The doc string for add-variable-watcher wrongly states:

    Cause WATCH-FUNCTION to be called when SYMBOL is set.

.  Correct would be either

    Cause WATCH-FUNCTION to be called just before SYMBOL is set.

or

    Cause WATCH-FUNCTION to be called just after SYMBOL is set.

.  I'm guessing that the first of these applies, but I shouldn't have to
guess.  The difference is whether one can get the old value from SYMBOL
or not.

The documentation in the Elisp manual is similarly ambiguous.  It uses
the conjunction "whenever".

-- 
Alan Mackenzie (Nuremberg, Germany).

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