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bug#34708: alist-get has unclear documentation
From: |
Michael Heerdegen |
Subject: |
bug#34708: alist-get has unclear documentation |
Date: |
Mon, 11 Mar 2019 14:39:00 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
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.
- bug#34708: alist-get has unclear documentation, (continued)
- bug#34708: alist-get has unclear documentation, Drew Adams, 2019/03/03
- bug#34708: alist-get has unclear documentation, Eric Abrahamsen, 2019/03/03
- bug#34708: alist-get has unclear documentation, Eric Abrahamsen, 2019/03/04
- bug#34708: alist-get has unclear documentation, Michael Heerdegen, 2019/03/04
- bug#34708: alist-get has unclear documentation, Eric Abrahamsen, 2019/03/04
- bug#34708: alist-get has unclear documentation, Michael Heerdegen, 2019/03/04
- bug#34708: alist-get has unclear documentation, Eric Abrahamsen, 2019/03/04
- bug#34708: alist-get has unclear documentation, Michael Heerdegen, 2019/03/05
- bug#34708: alist-get has unclear documentation, Eric Abrahamsen, 2019/03/05
- bug#34708: alist-get has unclear documentation, Drew Adams, 2019/03/05
- bug#34708: alist-get has unclear documentation,
Michael Heerdegen <=
- bug#34708: alist-get has unclear documentation, Drew Adams, 2019/03/11
- bug#34708: alist-get has unclear documentation, Michael Heerdegen, 2019/03/11
- bug#34708: alist-get has unclear documentation, Drew Adams, 2019/03/11
- bug#34708: alist-get has unclear documentation, Michael Heerdegen, 2019/03/12
- bug#34708: alist-get has unclear documentation, Drew Adams, 2019/03/12
- bug#34708: alist-get has unclear documentation, Michael Heerdegen, 2019/03/12
- bug#34708: alist-get has unclear documentation, Drew Adams, 2019/03/12
- bug#34708: alist-get has unclear documentation, Michael Heerdegen, 2019/03/12
- bug#34708: alist-get has unclear documentation, Michael Heerdegen, 2019/03/12
- bug#34708: alist-get has unclear documentation, Drew Adams, 2019/03/12