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bug#34708: alist-get has unclear documentation
From: |
Drew Adams |
Subject: |
bug#34708: alist-get has unclear documentation |
Date: |
Tue, 12 Mar 2019 07:53:13 -0700 (PDT) |
> > > (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?
> >
> > Sounds like an implementation/design artifact. If that will stay as
> > part of the design then yes, I'd say such behavior needs to be
> > documented.
>
> BTW with a different viewpoint, when you use
> (setcdr (assoc 'a my-alist) 17)
>
> on the above degenerated alist you also change _both_ of the 'a
> associations, so one could argue that the `alist-get' setter behaves
> correctly when removing both: there are not two 'a associations in
> MY-ALIST but the same one has just been added two times, so it's correct
> to remove both of them.
OK. Put it differently: it's worth documenting
that updating an alist entry with `setf' is a
"destructive" operation: it can change list
structure. Dunno whether that is already said
somewhere, but even if it is, a reminder wouldn't
hurt.
- bug#34708: alist-get has unclear documentation, (continued)
- 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, 2019/03/11
- 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 <=
- 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, 2019/03/15
- bug#34708: alist-get has unclear documentation, Eric Abrahamsen, 2019/03/15
- bug#34708: alist-get has unclear documentation, Michael Heerdegen, 2019/03/27