bug#27584: 26.0.50; alist-get: Add optional arg TESTFN

[Tino Calancha]

On Sat, 8 Jul 2017, Eli Zaretskii wrote:

> > From: Nicolas Petton <nicolas@petton.fr>
> > Cc: monnier@iro.umontreal.ca, 27584@debbugs.gnu.org
> > Date: Sat, 08 Jul 2017 13:32:11 +0200
> >
> > > That's one way, yes.  But not necessarily the one I had in mind.
> >
> > What solution did you have in mind?
>
> Something like this:
>
>  FOR_EACH_TAIL (tail)
>    {
>      Lisp_Object car = XCAR (tail);
>      if (CONSP (car)
>           && (NILP (testfn)
>               ? (EQ (XCAR (car), key) || !NILP (Fequal (XCAR (car), key)))
>               : !NILP (call2 (testfn, XCAR (car), key))))
>         return car;
>    }
Nice!