From: Stefan Monnier via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>
To: help-gnu-emacs@gnu.org
Subject: Re: How are regexen implemented in Emacs?
Date: Mon, 12 Dec 2022 16:24:54 -0500 [thread overview]
Message-ID: <jwvcz8ofhbf.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: 874ju0e52e.fsf@mbork.pl
> Very interesting. Re: back references, are even "regexen" with back
> references still real regular expressions?
No, back references aren't part of the "regular language" family.
They can't easily be accommodated by the usual DFA/NFA
non-backtracking matchers (and IIRC they are fundamentally
exponential-complexity in the worst case), tho some do handle them
(by falling back to a backtracking algorithm, AFAIK).
Stefan
next prev parent reply other threads:[~2022-12-12 21:24 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-12 17:15 How are regexen implemented in Emacs? Marcin Borkowski
2022-12-12 18:16 ` Stefan Monnier via Users list for the GNU Emacs text editor
2022-12-12 19:09 ` Marcin Borkowski
2022-12-12 19:17 ` Stefan Monnier via Users list for the GNU Emacs text editor
2022-12-12 20:31 ` Marcin Borkowski
2022-12-12 21:19 ` Stefan Monnier
2022-12-13 5:01 ` tomas
2022-12-13 16:16 ` Stefan Monnier via Users list for the GNU Emacs text editor
2022-12-15 5:22 ` Emanuel Berg
2022-12-16 17:39 ` Akib Azmain Turja
2022-12-17 0:31 ` Emanuel Berg
2022-12-18 0:54 ` Jean Louis
2022-12-19 20:31 ` Emanuel Berg
2022-12-12 20:01 ` tomas
2022-12-12 20:32 ` Marcin Borkowski
2022-12-12 21:24 ` Stefan Monnier via Users list for the GNU Emacs text editor [this message]
2022-12-15 5:18 ` Emanuel Berg
2022-12-15 13:38 ` tomas
2022-12-15 16:46 ` Stefan Monnier via Users list for the GNU Emacs text editor
2022-12-15 17:56 ` tomas
2022-12-17 0:13 ` Emanuel Berg
2022-12-15 3:45 ` Emanuel Berg
2022-12-15 13:22 ` tomas
2022-12-15 3:41 ` Emanuel Berg
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