From: "Mattias Engdegård" <mattiase@acm.org>
To: Paul Eggert <eggert@cs.ucla.edu>
Cc: 37659@debbugs.gnu.org
Subject: bug#37659: rx additions: anychar, unmatchable, unordered-or
Date: Tue, 22 Oct 2019 17:14:08 +0200 [thread overview]
Message-ID: <88571301-3F15-428F-82F9-60A23D817EF8@acm.org> (raw)
In-Reply-To: <b67ac191-9c7f-02bc-367c-206ac9584981@cs.ucla.edu>
'regexp-opt' always generates a regexp preferring long matches. This is undocumented, but useful enough that I would be surprised if this property wasn't exploited (perhaps unknowingly) by callers. It's quite natural: given a set of strings, surely the caller want them all to be candidates for a match, even if there is no following anchoring pattern.
Thus, instead of 'unordered-or', define the operator in terms of long matches: 'or-max' (working name) would work like 'or' but guarantee a longest match, and only permit strings and 'or-max' forms as arguments. Thus, the rx user gets all the benefits from 'regexp-opt' in a composable way, without a need to sort the strings or otherwise prepare them.
(The old 'or' behaviour always used 'regexp-opt' when possible, which was very fragile: (or "a" "ab") would match "ab", but (or "a" "ab" digit) would just match "a". 'or-max' is robust, without surprises.)
Of course, we should also guarantee the maximum-matching property of regexp-opt. This is just a matter of documentation (and test); it does not restrict optimisations as far as I can tell.
Again, I'm open to suggestions about a better name than 'or-max'.
The other patches (anychar, unmatchable, and [^z-a]) have been pushed to master.
next prev parent reply other threads:[~2019-10-22 15:14 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-08 9:36 bug#37659: rx additions: anychar, unmatchable, unordered-or Mattias Engdegård
2019-10-09 8:59 ` Mattias Engdegård
2019-10-11 23:07 ` bug#37659: Mattias Engdegård <mattiase <at> acm.org> Paul Eggert
2019-10-12 10:47 ` Mattias Engdegård
2019-10-13 16:52 ` Paul Eggert
2019-10-13 19:48 ` Mattias Engdegård
2019-10-22 15:14 ` Mattias Engdegård [this message]
2019-10-22 15:27 ` bug#37659: rx additions: anychar, unmatchable, unordered-or Robert Pluim
2019-10-22 17:33 ` Paul Eggert
2019-10-23 9:15 ` Mattias Engdegård
2019-10-23 23:14 ` Paul Eggert
2019-10-24 1:56 ` Drew Adams
2019-10-24 9:09 ` Mattias Engdegård
2019-10-24 14:24 ` Drew Adams
2019-10-24 9:17 ` Phil Sainty
2019-10-24 14:32 ` Drew Adams
2019-10-24 8:58 ` Mattias Engdegård
2019-10-27 11:53 ` Mattias Engdegård
2020-02-11 12:57 ` Mattias Engdegård
2020-02-11 15:43 ` Eli Zaretskii
2020-02-11 19:17 ` Mattias Engdegård
2020-02-12 0:52 ` Paul Eggert
2020-02-12 11:22 ` Mattias Engdegård
2020-02-13 18:38 ` Mattias Engdegård
2020-02-13 18:50 ` Paul Eggert
2020-02-13 19:16 ` Mattias Engdegård
2020-02-13 19:30 ` Eli Zaretskii
2020-02-13 22:23 ` Mattias Engdegård
2020-02-14 7:45 ` Eli Zaretskii
2020-02-14 16:15 ` Paul Eggert
2020-02-14 20:49 ` Mattias Engdegård
2020-03-01 10:09 ` Mattias Engdegård
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