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 17:19:51 +0100 [thread overview]
Message-ID: <87wol5l6xk.fsf@web.de> (raw)
In-Reply-To: <3af3b645-84e0-4208-be48-810e8cd2cfa8@default> (Drew Adams's message of "Mon, 11 Mar 2019 07:52:31 -0700 (PDT)")
Drew Adams <drew.adams@oracle.com> writes:
> > (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.
>
> I think so, yes. Why wouldn't we want to allow that?
To not add one more argument?
If we do that, I guess I would rather allow that the non-nil value of
REMOVE is allowed to be a function. A related use case would be to
allow to delete the association of a key independently from associated
value.
> > (2) The remove feature has a strange corner case. Normally the
> > first found association is removed,
>
> So "normally" it's really "remove one".
>
> Why is this? What's the point of REMOVE - why is
> it needed (added to the design) at all? Is it to
> provide a way to remove all entries with a given
> key or only the first such?
The first.
> If we want to provide for pretty much everything
> that one typically does with an alist (without
> `alist-get') then don't we need to provide for the
> ability to do any kind of removal - or other
> operations - on alist elements that have a given key?
>
> Should "set" and "remove" operations not (at least
> be able to) obtain the _full_ sequence (in entry
> order) of such matching elements, and then perform
> specific operations on that sequence (such as setting
> or removing the first one, the Nth one, or all of
> them)?
>
> If we were not trying to allow `alist-get' to be
> usable as a generalized variable then I suppose
> we wouldn't need to worry about any of this.
We tried. I think the result should be consistent and convenient, but
we don't need to implement all realizations of all operations for the
generalized variable.
One thing I don't find consistent is the case where the alist already
has multiple occurrences of a key. E.g.
(setq my-alist '((a . 1) (b . 2) (a . -1)))
(setf (alist-get 'a my-alist 1 'remove) 1)
my-alist ==> ((b . 2) (a . -1))
(alist-get 'a my-alist 1)
==> -1 (!)
One would expect 1, of course.
> It would be good to see a statement/spec of what
> `alist-get' is trying to accomplish, especially
> wrt setting, testing (diff predicates), and
> removing.
Yes, this is what my patch will try to accomplish.
Michael.
next prev parent reply other threads:[~2019-03-11 16:19 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
2019-03-11 14:52 ` Drew Adams
2019-03-11 16:19 ` Michael Heerdegen [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87wol5l6xk.fsf@web.de \
--to=michael_heerdegen@web.de \
--cc=34708@debbugs.gnu.org \
--cc=drew.adams@oracle.com \
--cc=eric@ericabrahamsen.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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.