From: <tomas@tuxteam.de>
To: help-gnu-emacs@gnu.org
Subject: Re: How are regexen implemented in Emacs?
Date: Thu, 15 Dec 2022 14:38:45 +0100 [thread overview]
Message-ID: <Y5sjZR+RSZDwxQaV@tuxteam.de> (raw)
In-Reply-To: <87r0x1utw3.fsf@dataswamp.org>
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On Thu, Dec 15, 2022 at 06:18:36AM +0100, Emanuel Berg wrote:
[...]
> A set of rules crunches the input and determines transitions
> from one state to another, I can imagine deterministic such
> rules - but nondeterministic, what does that mean?
>
> Maybe that from one state S and input I there are not one but
> several ways to go, one can go to S' but also S'' and both
> "moves" are legal?
Exactly. The naive implementation of which involves keeping
a queue of possible states (breadth-first search).
Thompson's trick is converting the NFA into a DFA by considering
"sets of (possible) states" as your new states. But now you've
got 2^n states; the clever part is how to reduce that to some
manageable state space.
I think the Wikipedia has good articles on that.
Cheers
--
t
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next prev parent reply other threads:[~2022-12-15 13:38 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
2022-12-15 5:18 ` Emanuel Berg
2022-12-15 13:38 ` tomas [this message]
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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