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From: "Mattias Engdegård" <mattiase@acm.org>
To: phs@lsv.fr
Cc: Michael Heerdegen <michael_heerdegen@web.de>,
	Stefan Monnier <monnier@iro.umontreal.ca>,
	emacs-devel@gnu.org
Subject: Re: More re odditie [Was: regular expressions that match nothing]
Date: Thu, 16 May 2019 11:29:24 +0200	[thread overview]
Message-ID: <ABAFE6B8-9CAE-4CEA-A516-6A636CAA1132@acm.org> (raw)
In-Reply-To: <84fcfdce-39d7-1ebb-c0c7-98aa05854646@lsv.fr>

16 maj 2019 kl. 08.57 skrev phs <phs@lsv.fr>:
> 
> The regular expression "*", instead of matching zero-or-more occurrences
> of the empty string, behaves as "\*" or "[*]" and only matches the *
> character.
> 
> I believe this is a bug, not a feature, and in any case the Emacs manual
> does not document this behavior.

Actually this one is documented:

  For historical compatibility, special characters are treated as ordinary
  ones if they are in contexts where their special meanings make no sense.
  For example, `*foo' treats `*' as ordinary since there is no preceding
  expression on which the `*' can act.

and in any case the 'correct' behaviour would be to signal a syntax error, not repeat the empty string.

> If this behavior is the expected one, then (rx (0+ "")) should not
> return "*".

Thanks for reporting it, and you are right, that's a (known) bug in rx.




  reply	other threads:[~2019-05-16  9:29 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-14  7:25 regular expressions that match nothing philippe schnoebelen
2019-05-14 10:14 ` Mattias Engdegård
2019-05-14 19:41   ` Stefan Monnier
2019-05-15 16:21     ` Mattias Engdegård
2019-05-15 19:41       ` Alan Mackenzie
2019-05-16 10:54         ` Mattias Engdegård
2019-05-16 23:18           ` Phil Sainty
2019-05-17  9:43             ` Alan Mackenzie
2019-05-17 10:17               ` Mattias Engdegård
2019-05-17 12:53               ` Stefan Monnier
2019-05-15 20:17       ` Michael Heerdegen
2019-05-15 21:06         ` Stefan Monnier
2019-05-15 21:07         ` Mattias Engdegård
2019-05-15 21:38           ` Michael Heerdegen
2019-05-16  6:57           ` More re odditie [Was: regular expressions that match nothing] phs
2019-05-16  9:29             ` Mattias Engdegård [this message]
2019-05-16 10:59               ` phs
2019-05-16 12:31                 ` Stefan Monnier
2019-05-16 18:35             ` Michael Heerdegen
2019-05-16 20:31               ` Mattias Engdegård
2019-05-16 21:01                 ` Global and local definitions of non-functions/variable (was: More re odditie [Was: regular expressions that match nothing]) Stefan Monnier
2019-05-20 16:26           ` Bootstrap/autoload policy (was Re: regular expressions that match nothing) Mattias Engdegård
2019-05-22 14:02             ` Stefan Monnier
2019-05-22 14:07               ` Mattias Engdegård
2019-05-22 14:24                 ` Stefan Monnier
2019-05-22 15:06                   ` Mattias Engdegård
2019-05-22 15:53                     ` Stefan Monnier
2019-05-22 16:40                       ` Mattias Engdegård
2019-05-22 19:08                         ` Stefan Monnier
2019-05-26 12:05                         ` Basil L. Contovounesios
2019-05-16 18:12       ` regular expressions that match nothing Eric Abrahamsen
2019-05-19  4:30         ` 回复: " net june
2019-05-19  5:00           ` HaiJun Zhang
2019-05-19  7:32             ` Mattias Engdegård
2019-05-20  7:56               ` philippe schnoebelen
2019-05-20 23:19                 ` Richard Stallman
2019-05-19 14:12           ` 回复: " Drew Adams

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