GNU bug report logs - #47368
28.0.50; map-elt returns nil without "deprecated" TESTFN

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Message #11 received at 47368 <at> debbugs.gnu.org (full text, mbox):

From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: "Basil L. Contovounesios" <contovob <at> tcd.ie>
Cc: dalanicolai <dalanicolai <at> gmail.com>, 47368 <at> debbugs.gnu.org
Subject: Re: bug#47368: 28.0.50; map-elt returns nil without "deprecated"
 TESTFN
Date: Thu, 25 Mar 2021 03:39:14 +0100

"Basil L. Contovounesios" <contovob <at> tcd.ie> writes:

> dalanicolai <dalanicolai <at> gmail.com> writes:
>
> > The docstring of the map-elt function from the map.el package (version
> > 3.0) mentions that TESTFN is deprecated because "its default depends on
> > the MAP argument". However when I try e.g.
> >
> > (map-elt '(("A1" . 3)) "A1")
> >
> > it returns nil.
>
> This is expected, as alist keys are tested with eq by default.
>
> That's what the docstring is trying to warn about: alists default to
> testing with eq, but can also use eql, equal, or anything else.

Is it that obvious?  We have `assoc' and `assq' built-in - to me it's
not obvious that "alist keys are tested with eq by default".  It's the
default for `alist-get', ok, which is used by the implementation, but
not everybody will know that.  I would add a sentence about that.

Michael.

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