GNU bug report logs - #72328
[PATCH] Nested backquote in pcase

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Message #35 received at 72328 <at> debbugs.gnu.org (full text, mbox):

From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: Thuna <thuna.cing <at> gmail.com>
Cc: 72328 <at> debbugs.gnu.org
Subject: Re: bug#72328: [PATCH] Nested backquote in pcase
Date: Mon, 29 Jul 2024 22:45:08 +0200

Thuna <thuna.cing <at> gmail.com> writes:

> I feel like there is a possible misunderstanding.  I am not preventing a
> backquote pattern from going deeper into a list.  Your example would
> remain perfectly consistent under the new behavior.  What *wouldn't*,
> however, is something like
>
> (let ((a 1) (b 2))
>  (pcase `(69 foo `(,bar ,,a ((,,b))))
>    (`(69 foo `(,bar ,,a ((,,b))))
>     (list a b))))

Ok - so backquote the macro handles nested invocations of backquote
specially (the nested calls are not expanded individually, only the
outermost backquote expression gets expanded), while the pcase' backquote
implementation is backquote agnostic, it currently treats it like any
random symbol.  Your patch tries to adapt pcase backquote to the
backquote macro semantics.  Correct?

If there aren't any downsides then this makes a lot of sense and would
be a good thing to do indeed.

Let's wait for Stefan then.


Michael.

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