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From: Sebastian Gniazdowski <sgniazdowski@gmail.com>
To: Zsh hackers list <zsh-workers@zsh.org>
Subject: Extending regexes
Date: Mon, 4 Jul 2022 14:03:24 +0200	[thread overview]
Message-ID: <CAKc7PVAa718cFk2n1W=oxgxxRh-DEs8Cjvc5sKpqe8C3D+M-ig@mail.gmail.com> (raw)

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Zsh has extensions to regular regexes - the ~ and ^ negations. They, as it
can be expected from negations that are required by Turing universal
machines, introduce a whole new universe of computations over standard
regular expressions. For example matching in an AND fashion:

If [[ ABC == *A*~^*B*~^*C* ]]; then
  print A,  B and C found

I think that regexes look pretty limited from this point of view and that
pcre extensions went wrong path with the look forward and behind semantics.
The typical, common attempts of using regex [^] negation like [^(string)]
are simply there in zsh patterns as ^string.

I've recently used ~ negation in a project to reject a set of known tokens
from matching at given position with a great success to match a loose `for`
syntax in an zinit-annex-pull extension to zinit that greps and extracts
zinit commands from any web page. I cannot see it possible without the
extra negation.

Therefore I thought that it's weird that such an useful feature is missing
from the commonly used regex syntax. So maybe an attempt of updating it has
sense? Could someone experienced with them like Oliver prepare some white
papers to accomplish this? It would be a great event to extend the old
regexes with such a great feature like not one, but TWO new negations.

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             reply	other threads:[~2022-07-04 12:03 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-04 12:03 Sebastian Gniazdowski [this message]
2022-07-04 13:47 ` Peter Stephenson
2022-07-04 19:15   ` Bart Schaefer
2022-07-04 19:41     ` Peter Stephenson
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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