From: "Mattias Engdegård" <mattiase@acm.org>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: "Basil L. Contovounesios" <contovob@tcd.ie>,
Ag Ibragimov <agzam.ibragimov@gmail.com>,
emacs-devel@gnu.org
Subject: Re: Pattern matching on match-string groups #elisp #question
Date: Thu, 25 Feb 2021 19:28:16 +0100 [thread overview]
Message-ID: <80CE2366-76F4-4548-B956-F16DFCE23E4C@acm.org> (raw)
In-Reply-To: <jwvv9aggooq.fsf-monnier+emacs@gnu.org>
25 feb. 2021 kl. 16.32 skrev Stefan Monnier <monnier@iro.umontreal.ca>:
>> The same won't work with pcase-let, so it's either unsupported or a bug.
>
> I'd say it's a bug. The patch below would fix it. Mattias, WDYT?
Thank you, it looks like multiple bugs. The lack of (pred stringp) was of course an oversight but unrelated to pcase-let, right?
> (let* ((rx--pcase-vars nil)
> (regexp (rx--to-expr (rx--pcase-transform (cons 'seq regexps)))))
> - `(and (pred (string-match ,regexp))
> + `(and (pred stringp)
> + (app (lambda (s) (string-match ,regexp s)) (pred identity))
It does seem to work, but why exactly do we need this monstrosity instead of (pred (string-match ,regexp))? Is it because pcase-let throws away all `pred` clauses somewhere? It makes sense to do so but I haven't found exactly where this takes place in pcase.el yet...
Perhaps the assumption that non-binding clauses like `pred` (and what else, `guard`?) are all side-effect free and can be thrown away in pcase-let[*] should be documented? Not that I would have read it, of course...
I'll push a fix as soon as I understand the machinery a bit better, but right now I'm wary of getting my fingers snapped off by the gears and knives.
next prev parent reply other threads:[~2021-02-25 18:28 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-25 5:11 Pattern matching on match-string groups #elisp #question Ag Ibragimov
2021-02-25 14:55 ` Basil L. Contovounesios
2021-02-25 15:32 ` Stefan Monnier
2021-02-25 18:28 ` Mattias Engdegård [this message]
2021-02-26 4:31 ` Stefan Monnier
2021-02-26 10:24 ` Mattias Engdegård
2021-02-26 19:38 ` Stefan Monnier
2021-02-27 10:17 ` Mattias Engdegård
2021-02-27 14:39 ` Stefan Monnier
2021-02-27 18:10 ` Mattias Engdegård
2021-02-27 20:32 ` Stefan Monnier
2021-02-28 13:46 ` Mattias Engdegård
2021-02-28 15:37 ` Stefan Monnier
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