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From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Adam Porter <adam@alphapapa.net>
Cc: emacs-devel <emacs-devel@gnu.org>
Subject: Re: Make peg.el a built-in library?
Date: Sat, 02 Oct 2021 10:45:32 -0400	[thread overview]
Message-ID: <jwvtuhzmqty.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <CAO_b3FXRX-7h7yAE84z9rq-CCXYKmr8hk67on50F8wHcDd-zgg@mail.gmail.com> (Adam Porter's message of "Sat, 2 Oct 2021 02:32:22 -0500")

>> E.g. we could have a PEX of the form (re FORM) where FORM can be any
>> ELisp expression that returns a regular expression.  Then `org-ql.el`
>> could do
>>
>>     (let ((predicate-re (regexp-opt predicate-names)))
>>       (peg-parse
>>           ((query (+ term
>>                      (opt (+ (syntax-class whitespace) (any)))))
>>            [...]
>>            (predicate (re predicate-re))
>>            [...])))
>
> That would be helpful, yes.

Thanks, I'll think about what can be done here.

>> PS: BTW, regarding your comment:
>>
>>         ;; Sort the keywords longest-first to work around what seems to be an
>>         ;; obscure bug in `peg': when one keyword is a substring of another,
>>         ;; and the shorter one is listed first, the shorter one fails to match.
>>
>> The behavior you describe indeed seems like a bug, but maybe what you
>> see is slightly different (and not a bug): if you have a PEX like
>> (and (or "foo" "foobar") "X")
>> the "foo" will match when faced with "foobarX" and the parser won't
>> backtrack to try and match the "foobar" when the "X" fails to match.
>
> Hmm, thanks.  I think an example of the problem is that a predicate in
> org-ql might have a shorter alias, e.g. "heading" is has the alias
> "h", and predicates are followed by arguments, like "heading:foo", so
> IIRC, without sorting them there, "heading:foo" would work, while
> "h:foo" wouldn't.

Odd.  If you have (or "h" "header") in the grammar then I'd expect
"h:foo" to be recognized but "heading:foo" to be rejected (IOW, that
would be a bug in the grammar rather than in `peg.el`).

But you describe the exact opposite for which I don't have
an explanation.  So maybe it's a bug in `peg.el`.  Could you try and
distill it into a bug report?


        Stefan




  reply	other threads:[~2021-10-02 14:45 UTC|newest]

Thread overview: 100+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-25 18:52 Make peg.el a built-in library? Eric Abrahamsen
2021-08-26  6:17 ` Eli Zaretskii
2021-08-26 15:34   ` Eric Abrahamsen
2021-09-09  4:36     ` Eric Abrahamsen
2021-09-19 15:25       ` Eric Abrahamsen
2021-09-30 19:44       ` Stefan Monnier
2021-09-30 20:34         ` Adam Porter
2021-10-01  8:14           ` Augusto Stoffel
2021-10-01 18:05           ` Stefan Monnier
2021-10-01 18:40             ` Eric Abrahamsen
2021-10-02  3:57               ` Stefan Monnier
2021-10-02  7:32             ` Adam Porter
2021-10-02 14:45               ` Stefan Monnier [this message]
2021-10-02 15:13                 ` Adam Porter
2021-08-26 17:02 ` Adam Porter
2021-08-26 17:25   ` Eric Abrahamsen
2021-08-27  3:17   ` Eric Abrahamsen
2021-08-27  6:41     ` Helmut Eller
2021-08-27 16:57       ` Eric Abrahamsen
2021-09-26 10:59       ` Augusto Stoffel
2021-09-26 15:06         ` Eric Abrahamsen
2021-09-26 18:36           ` Augusto Stoffel
2021-09-27 16:18             ` Eric Abrahamsen
2021-09-27 22:34         ` Richard Stallman
2021-09-28  3:52           ` Eric Abrahamsen
2021-09-28  8:09             ` tomas
2021-09-28  9:32               ` Helmut Eller
2021-09-28 10:45                 ` tomas
2021-09-28 15:24               ` Augusto Stoffel
2021-09-30  6:04             ` Richard Stallman
2021-10-01  3:27               ` Eric Abrahamsen
2021-10-09  1:31 ` Michael Heerdegen
2021-10-09  5:28   ` Michael Heerdegen
2021-10-09  8:12     ` Helmut Eller
2021-10-09 12:52       ` Stefan Monnier
2021-10-10  5:49         ` Helmut Eller
2021-10-14 10:25       ` Michael Heerdegen
2021-10-09 12:54   ` Stefan Monnier
2021-10-09 16:47     ` Eric Abrahamsen
2021-10-10  4:20       ` Michael Heerdegen
2021-10-10 21:40         ` Eric Abrahamsen
2021-10-13  2:58           ` Michael Heerdegen
2021-10-09 16:49   ` Eric Abrahamsen
2021-10-10  3:43     ` Stefan Monnier
2021-10-10  4:46       ` Michael Heerdegen
2021-10-10  5:58         ` Helmut Eller
2021-10-10 13:56           ` Stefan Monnier
2021-10-22 16:33           ` Michael Heerdegen
2021-10-31 23:43           ` Michael Heerdegen
2021-11-15 23:16             ` Michael Heerdegen
2022-11-07  3:33 ` Ihor Radchenko
2022-11-07 19:46   ` Eric Abrahamsen
2022-11-08  6:57     ` Helmut Eller
2022-11-08  8:51       ` Ihor Radchenko
2022-11-10  4:04       ` Richard Stallman
2022-11-10  5:25         ` tomas
2022-11-10  8:15           ` Eli Zaretskii
2022-11-10  8:29             ` tomas
2022-11-11  4:36           ` Richard Stallman
2022-11-08  8:47     ` Ihor Radchenko
2022-11-08 16:18       ` Eric Abrahamsen
2022-11-08 19:08         ` tomas
2022-11-08 19:42           ` Eric Abrahamsen
2022-11-16  4:27             ` [PATCH] " Eric Abrahamsen
2022-11-16  5:07               ` tomas
2022-11-16  5:39                 ` Eric Abrahamsen
2022-11-16 15:53                   ` tomas
2022-11-16  6:24               ` Ihor Radchenko
2022-11-16 18:15                 ` Eric Abrahamsen
2022-11-17 12:21                   ` Ihor Radchenko
2022-11-27  1:46                     ` Eric Abrahamsen
2022-11-27  8:57                       ` Eli Zaretskii
2022-11-28  1:09                         ` Eric Abrahamsen
2022-11-28 12:16                           ` Eli Zaretskii
2023-09-25  1:30                             ` Eric Abrahamsen
2023-09-25  2:27                               ` Adam Porter
2023-09-25 13:00                                 ` Alexander Adolf
2024-03-24 14:19                               ` Ihor Radchenko
2024-03-24 15:32                                 ` Eli Zaretskii
2024-03-25  1:45                                   ` Eric Abrahamsen
2023-01-11  7:39               ` Michael Heerdegen
2023-01-11  8:04                 ` Ihor Radchenko
2023-01-11 11:01                   ` Michael Heerdegen
2023-01-11 11:32                     ` tomas
2023-02-05 12:10                     ` Ihor Radchenko
2023-02-05 15:41                       ` Eduardo Ochs
2023-02-05 15:45                         ` Ihor Radchenko
2023-02-05 16:19                           ` Eduardo Ochs
2023-02-05 16:50                             ` Ihor Radchenko
2023-02-09  5:44                         ` Jean Louis
2023-02-06  0:33                       ` Michael Heerdegen
2022-11-08 14:01     ` Stefan Monnier
2022-11-08 14:42       ` tomas
2022-11-08 15:08       ` Visuwesh
2022-11-08 16:29         ` Juanma Barranquero
2022-12-02 20:20           ` Augusto Stoffel
2022-11-08 16:10       ` Eric Abrahamsen
2022-11-08 18:59         ` tomas
2022-11-08 19:42           ` Eric Abrahamsen
2022-11-08 22:03             ` Tim Cross

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