From: Daniel Colascione <dancol@dancol.org>
To: "Perry E. Metzger" <perry@piermont.com>
Cc: Stefan Monnier <monnier@iro.umontreal.ca>, emacs-devel@gnu.org
Subject: Re: [Emacs-diffs] master 938d252 4/4: Make regex matching reentrant; update syntax during match
Date: Tue, 19 Jun 2018 07:48:28 -0700 [thread overview]
Message-ID: <9a5f3904-8298-b5e3-cd97-b525f602cc63@dancol.org> (raw)
In-Reply-To: <20180619103325.7d79befb@jabberwock.cb.piermont.com>
On 06/19/2018 07:33 AM, Perry E. Metzger wrote:
> On Tue, 19 Jun 2018 10:30:02 -0400 "Perry E. Metzger"
> <perry@piermont.com> wrote:
>>>> Oh, and re2 isn't built for POSIX compliance. It has no
>>>> constructs that require backtracking etc.
>>>
>>> No DFA engine can do backtracking.
>>
>> Correct, but there are regexp libraries that will switch between DFA
>> and non-DFA implementations depending on whether the regexp has
>> constructs in it that require backtracking.
>
> Just to be explicit: TRE does this, IIRC. It certainly implements
> backreferences, which re2 does not. (And, it has provisions in its
> API for handling things like gap buffers. The main problem is it is
> unmaintained.)
If we did want to adopt TRE, we'd have to add supports for PCRE-like
callouts for implementing Emacs-specific assertions. (PCRE itself has
the opposite problem: explicit support for pluggable callouts, but no
support for an iterator API.)
I'd also like to better understand the specific remaining differences
between POSIX regular expression semantics and what TRE implements,
whether this difference is intentional or not. And I'd also like to
understand how we can give the engine Emacs-regex semantics instead of
POSIX ones. (Very few people use the POSIX mode of Emacs regex matching.)
I'm also not sure how copyright assignment would work for abandonware.
next prev parent reply other threads:[~2018-06-19 14:48 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20180616204650.8423.73499@vcs0.savannah.gnu.org>
[not found] ` <20180616204653.86AFC203CB@vcs0.savannah.gnu.org>
2018-06-17 18:42 ` [Emacs-diffs] master 938d252 4/4: Make regex matching reentrant; update syntax during match Stefan Monnier
2018-06-17 18:51 ` Daniel Colascione
2018-06-17 19:18 ` Daniel Colascione
2018-06-17 19:34 ` Stefan Monnier
2018-06-17 19:50 ` Daniel Colascione
2018-06-17 19:30 ` Stefan Monnier
2018-06-18 15:59 ` Perry E. Metzger
2018-06-18 17:49 ` Daniel Colascione
2018-06-19 13:40 ` Perry E. Metzger
2018-06-19 13:44 ` Perry E. Metzger
2018-06-19 13:49 ` Daniel Colascione
2018-06-19 14:30 ` Perry E. Metzger
2018-06-19 14:33 ` Perry E. Metzger
2018-06-19 14:48 ` Daniel Colascione [this message]
2018-06-19 15:37 ` Perry E. Metzger
2018-06-19 16:20 ` Paul Eggert
2018-06-19 16:27 ` Perry E. Metzger
2018-06-19 17:46 ` Stefan Monnier
2018-06-19 18:18 ` Daniel Colascione
2018-06-19 18:26 ` Perry E. Metzger
2018-06-19 16:54 ` John Wiegley
2018-06-19 17:04 ` Perry E. Metzger
2018-06-19 18:20 ` John Wiegley
2018-06-19 18:04 ` Paul Eggert
2018-06-19 18:16 ` Daniel Colascione
2018-06-19 18:26 ` Paul Eggert
2018-06-19 18:03 ` Andreas Schwab
2018-06-19 18:48 ` Paul Eggert
2018-06-19 14:46 ` Daniel Colascione
2018-06-19 14:58 ` Andreas Schwab
2018-06-19 15:32 ` Perry E. Metzger
2018-06-18 23:25 ` Richard Stallman
2018-06-19 1:30 ` Perry E. Metzger
2018-06-19 22:54 ` Richard Stallman
2018-06-20 1:17 ` Perry E. Metzger
2018-06-20 23:26 ` Richard Stallman
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