GNU bug report logs - #75594
31.0.50; [FR]: Change equality test for Pcase non-linear patterns

Previous Next

Full log

View this message in rfc822 format

From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: Eshel Yaron <me <at> eshelyaron.com>
Cc: 75594 <at> debbugs.gnu.org, Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: bug#75594: 31.0.50; [FR]: Change equality test for Pcase non-linear patterns
Date: Fri, 17 Jan 2025 02:01:47 +0100

Eshel Yaron <me <at> eshelyaron.com> writes:

> > I can see two possible syntax options:
> >
> > 1- some kind of "contextual" pcase macro like
> >
> >     (with-equality-predicate #'equal
> >       `(,foo ,foo ,foo))
> >
> > 2- some kind of VAR pattern but annotated with an equality predicate in
> >    case this is not the first use of this identifier, so you'd write
> >
> >     `(,(var foo #'equal) ,(var foo #'equal) ,(var foo #'equal))
>
> Both options sound good.  The need to repeat the equality predicate
> multiple times in option 2 makes it slightly less preferable, but it
> maybe it'd be easier to document/explain.

2 has the advantage that it allows mixing different predicates.  Dunno
if this is often useful, though.

I wonder how typical examples of this feature look like.  So far I
stumbled over the implicit equivalence test not being what I needed
sometimes, but not really often.

(Of course I'm open to add something (maybe more) convenient to el-search
if it is useful.)


Michael.

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.