From: Bruno Barbier <brubar.cs@gmail.com>
To: Marco Antoniotti <marcoxa@gmail.com>
Cc: 70597@debbugs.gnu.org
Subject: bug#70597: Problem in pcase-let?
Date: Sun, 28 Apr 2024 12:01:18 +0200 [thread overview]
Message-ID: <662e1e70.050a0220.3a3a2.45d1@mx.google.com> (raw)
In-Reply-To: <CAKmY7cXKs_AE_2yBt9CcV7tTkeT4bz0oYFBcadjCfk90b2H00w@mail.gmail.com>
Hi Marco,
Marco Antoniotti <marcoxa@gmail.com> writes:
> Hi Bruno
>
> Thank you for the reply, but sorry. IMHO it is a bug, At a minimum,
> because pcase and pcase-let behave differently.
> I may be inclined to accept the explanation that the documentation about
> pcase-let allows for the behavior I find incorrect; that does not mean that
> the behavior is what is normally expected.
>
> Pattern matchers do ... pattern matching. If you allow quasiquotes or
> "incomplete specifications" (pick your preferred pattern matching
> terminology), then you should honor the expectations; hence two symbols
> that are not eq do not match.
So, you would prefer for pcase-let to always signal an error if a
pattern doesn't match. It makes sense.
And it looks like the issue has already been raised: see bug#19670.
(see https://debbugs.gnu.org/cgi/bugreport.cgi?bug=19670)
> Also note that I do not have any star (*) operators in my examples.
Thanks for mentionning this. I now see that you carefully crafted
your HTML version, but, I only used the text version (that is less
readable and contains plenty of stars). Sorry about the noise,
explaining how to parse generated lightweight markup as elisp :)
> Again, the machinery is there, cfr, the example below, which selects the
> second clause.
>
> ELISP>
>
> *(pcase '(1 2 3 4) (`(1 2 ,x 5) (list 42 x)) (`(1 ,x 3
> 4) (list 666 x)))*
> *(666 2)*
I'm not sure it's that obvious: pcase doesn't really make a difference
between match and no match:
(eq (pcase 'b (`a t) (`b nil))
(pcase 'c (`a t) (`b nil)))
==> t
If your request is really like bug#19670, further discussion should
probably go there.
All the best,
Bruno
next prev parent reply other threads:[~2024-04-28 10:01 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-26 18:00 bug#70597: Problem in pcase-let? Marco Antoniotti
2024-04-27 16:11 ` Bruno Barbier
2024-04-27 22:28 ` Marco Antoniotti
2024-04-28 10:01 ` Bruno Barbier [this message]
2024-04-28 10:07 ` Ihor Radchenko
2024-04-28 10:18 ` Eli Zaretskii
2024-04-28 15:22 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-04-28 15:38 ` Marco Antoniotti
2024-04-28 17:05 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-04-28 18:22 ` Marco Antoniotti
2024-04-28 21:08 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-05-02 9:23 ` Eli Zaretskii
2024-05-02 11:06 ` Marco Antoniotti
2024-05-04 11:35 ` Eli Zaretskii
2024-05-04 12:06 ` Marco Antoniotti
2024-05-04 15:05 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-05-05 8:49 ` Marco Antoniotti
2024-05-04 15:23 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
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