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From: Peter Stephenson <p.w.stephenson@ntlworld.com>
To: Zsh hackers list <zsh-workers@zsh.org>
Subject: Re: Extending regexes
Date: Mon, 4 Jul 2022 20:41:28 +0100 (BST)	[thread overview]
Message-ID: <1754611311.1326396.1656963688860@mail2.virginmedia.com> (raw)
In-Reply-To: <CAH+w=7bey3h8XzyxXcYiOXx3yzYk50cjm5t4yt5kGNWB-6XJdw@mail.gmail.com>

> On 04 July 2022 at 20:15 Bart Schaefer <schaefer@brasslantern.com> wrote:
> On Mon, Jul 4, 2022 at 6:53 AM Peter Stephenson
> <p.w.stephenson@ntlworld.com> wrote:>
> > > On 04 July 2022 at 13:03 Sebastian Gniazdowski <sgniazdowski@gmail.com> wrote:
> > > Zsh has extensions to regular regexes - the ~ and ^ negations.
> PWS correct me if I go too far astray, but (^Y) is internally (*~Y)
> and (X~Y) is implemented by first matching (X) and then removing
> anything that matches (Y) ... which is where the regular-ness goes
> astray.  My formal training on this is more than a little rusty, but I
> believe this means chaining together two finite-state machines rather
> than building a single one.

That is basically how they're implemented. We have a sort of internal
scratchpad that allows us to backtrack over the exclusions as a nested
state of the main pattern match. You're entitled to say 'ick' at this


  reply	other threads:[~2022-07-04 19:41 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-04 12:03 Sebastian Gniazdowski
2022-07-04 13:47 ` Peter Stephenson
2022-07-04 19:15   ` Bart Schaefer
2022-07-04 19:41     ` Peter Stephenson [this message]
2022-07-06 10:03       ` Daniel Shahaf
2022-07-06 18:40   ` stephane
2022-07-06 23:07 ` Phil Pennock
2022-07-07  0:22   ` Bart Schaefer

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