From: Michael Heerdegen <michael_heerdegen@web.de>
To: Drew Adams <drew.adams@oracle.com>
Cc: Eric Abrahamsen <eric@ericabrahamsen.net>, 34708@debbugs.gnu.org
Subject: bug#34708: alist-get has unclear documentation
Date: Mon, 11 Mar 2019 14:39:00 +0100 [thread overview]
Message-ID: <8736ntmsy3.fsf@web.de> (raw)
In-Reply-To: <60367f47-c0b0-45b4-8ccf-169044400a75@default> (Drew Adams's message of "Tue, 5 Mar 2019 16:16:19 -0800 (PST)")
Drew Adams <drew.adams@oracle.com> writes:
> Alists can be handled in more than one way when
> setting and deleting keys. The doc needs to tell
> us what `setf' with `alist-get' does to realize
> these things.
I agree.
I'm in the middle of preparing a patch. While doing that, two questions
arose:
(1) "When using it to set a value, optional argument REMOVE non-nil
means to remove KEY from ALIST if the new value is `eql' to DEFAULT."
I wonder if there are use cases where the user wants something different
than `eql'? E.g. `equal' when the associations are strings? Note that
this is something different than TESTFN which is for comparing keys.
(2) The remove feature has a strange corner case. Normally the first
found association is removed, but if you somehow manage to add the same
cons (in the sense of `eq') to the same alist, all of them are removed.
Compare e.g.
(progn
(setq my-alist '((a . 1) (a . 1) (b . 2)))
(setf (alist-get 'a my-alist nil 'remove) nil))
;; my-alist ==> ((a . 1) (b . 2))
vs.
(progn
(setq my-alist '((a . 1) (b . 2)))
(push (car my-alist) my-alist) ;; my-alist ==> (#1=(a . 1) #1# (b . 2))
(setf (alist-get 'a my-alist nil 'remove) nil))
;; my-alist ==> ((b . 2))
This is because the code uses delq to delete a found cons, and delq
removes all `eq' elements.
Is it worth to document or change that?
Michael.
next prev parent reply other threads:[~2019-03-11 13:39 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-02 4:50 bug#34708: alist-get has unclear documentation Miguel V. S. Frasson
2019-03-02 9:25 ` Michael Heerdegen
2019-03-02 15:40 ` Miguel V. S. Frasson
2019-03-02 18:10 ` Michael Heerdegen
2019-03-02 19:06 ` Eric Abrahamsen
2019-03-03 0:15 ` Phil Sainty
2019-03-03 12:50 ` Michael Heerdegen
2019-03-19 1:35 ` Michael Heerdegen
2019-03-02 19:51 ` Miguel V. S. Frasson
2019-03-02 20:32 ` Eric Abrahamsen
2019-03-03 11:32 ` Miguel V. S. Frasson
2019-03-03 12:21 ` Michael Heerdegen
2019-03-03 15:51 ` Drew Adams
2019-03-03 16:49 ` Eric Abrahamsen
2019-03-04 16:24 ` Eric Abrahamsen
2019-03-04 16:38 ` Michael Heerdegen
2019-03-04 17:16 ` Eric Abrahamsen
2019-03-04 18:22 ` Michael Heerdegen
2019-03-04 22:49 ` Eric Abrahamsen
2019-03-05 12:35 ` Michael Heerdegen
2019-03-05 22:50 ` Eric Abrahamsen
2019-03-06 0:16 ` Drew Adams
2019-03-11 13:39 ` Michael Heerdegen [this message]
2019-03-11 14:52 ` Drew Adams
2019-03-11 16:19 ` Michael Heerdegen
2019-03-11 17:48 ` Drew Adams
2019-03-12 13:04 ` Michael Heerdegen
2019-03-12 14:48 ` Drew Adams
2019-03-12 16:08 ` Michael Heerdegen
2019-03-12 16:48 ` Drew Adams
2019-03-12 17:45 ` Michael Heerdegen
2019-03-12 13:12 ` Michael Heerdegen
2019-03-12 14:53 ` Drew Adams
2019-03-12 15:38 ` Michael Heerdegen
2019-03-12 16:18 ` Drew Adams
2019-03-12 17:55 ` Michael Heerdegen
2019-03-15 15:54 ` Michael Heerdegen
2019-03-15 18:48 ` Eric Abrahamsen
2019-03-27 22:31 ` Michael Heerdegen
2019-04-19 1:33 ` Michael Heerdegen
2019-04-19 2:24 ` bug#34708: Thanks Miguel V. S. Frasson
2019-04-19 4:18 ` Michael Heerdegen
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