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Re: How are regexen implemented in Emacs?
From: |
tomas |
Subject: |
Re: How are regexen implemented in Emacs? |
Date: |
Mon, 12 Dec 2022 21:01:17 +0100 |
On Mon, Dec 12, 2022 at 08:09:42PM +0100, Marcin Borkowski wrote:
>
> On 2022-12-12, at 19:16, Stefan Monnier via Users list for the GNU Emacs text
> editor <help-gnu-emacs@gnu.org> wrote:
>
> >> https://www.gnu.org/software/emacs/manual/html_node/elisp/Regexp-Problems.html
> >> and started to wonder if the hints there mean that Emacs has a "naive",
> >> backtracking regex engine or a FA-based one?
> >
> > Naive!
>
> And what are the reasons? Out of curiosity: would implementing
> a FA-based one be a very big undertaking? (And no, I won't do it, if
> only because I don't know C.)
Nitpick: The Emacs regexp engine is a FA based one, but a DFA,
not a NFA (the famous Thompson NFA).
NFAs seem to be quite the beast, judging by how few implementations
are out there. I don't even know how easy it is to implement, e.g.
capture or (gasp!) back references,
Cheers
--
t
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- Re: How are regexen implemented in Emacs?, (continued)
- Re: How are regexen implemented in Emacs?, Stefan Monnier, 2022/12/12
- Re: How are regexen implemented in Emacs?, Marcin Borkowski, 2022/12/12
- Re: How are regexen implemented in Emacs?, Stefan Monnier, 2022/12/12
- Re: How are regexen implemented in Emacs?, tomas, 2022/12/13
- Re: How are regexen implemented in Emacs?, Stefan Monnier, 2022/12/13
- Re: How are regexen implemented in Emacs?, Emanuel Berg, 2022/12/15
- Re: How are regexen implemented in Emacs?, Akib Azmain Turja, 2022/12/16
- Re: How are regexen implemented in Emacs?, Emanuel Berg, 2022/12/17
- Re: How are regexen implemented in Emacs?, Jean Louis, 2022/12/18
- Re: How are regexen implemented in Emacs?, Emanuel Berg, 2022/12/20
- Re: How are regexen implemented in Emacs?,
tomas <=
- Re: How are regexen implemented in Emacs?, Marcin Borkowski, 2022/12/12
- Re: How are regexen implemented in Emacs?, Stefan Monnier, 2022/12/12
- Re: How are regexen implemented in Emacs?, Emanuel Berg, 2022/12/15
- Re: How are regexen implemented in Emacs?, tomas, 2022/12/15
- Re: How are regexen implemented in Emacs?, Stefan Monnier, 2022/12/15
- Re: How are regexen implemented in Emacs?, tomas, 2022/12/15
- Re: How are regexen implemented in Emacs?, Emanuel Berg, 2022/12/17
- Re: How are regexen implemented in Emacs?, Emanuel Berg, 2022/12/15
- Re: How are regexen implemented in Emacs?, tomas, 2022/12/15
Re: How are regexen implemented in Emacs?, Emanuel Berg, 2022/12/15