GNU bug report logs - #34708
alist-get has unclear documentation

Previous Next

Full log

Message #35 received at 34708 <at> debbugs.gnu.org (full text, mbox):

From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: Phil Sainty <psainty <at> orcon.net.nz>
Cc: Eric Abrahamsen <eric <at> ericabrahamsen.net>, 34708 <at> debbugs.gnu.org
Subject: Re: bug#34708: alist-get has unclear documentation
Date: Sun, 03 Mar 2019 13:50:51 +0100

Phil Sainty <psainty <at> orcon.net.nz> writes:

> Agreed.  I think the remove syntax is all but unreadable:
>
> (setf (alist-get KEY LIST t t) t)
>
> to remove items from LIST with key eq to KEY.
>
> Unless accompanied by comments, I do not think that meaning obvious
> at all.
>
> This variant gives a better idea...
>
> (setf (alist-get KEY LIST :remove :remove) :remove)

Yes, the syntax is a bit weird.  I think I would prefer to write it as

  (setf (alist-get key my-alist nil 'remove) nil)

The syntax also makes some sense: If you set the association of KEY to
the default that `alist-get' would return when the entry would not be
not found, the entry can be removed.  But I agree we should add such an
example, since not everybody wants to meditate over why this makes sense
in order to remember the syntax.


Michael.

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.