From: Bart Schaefer <schaefer@brasslantern.com>
To: Johan Grande <nahoj@crans.org>
Cc: zsh-workers@zsh.org
Subject: Re: Pattern bug on (a*|)~^(*b)
Date: Thu, 27 Jul 2023 18:02:30 -0700 [thread overview]
Message-ID: <CAH+w=7YodjiiFGGWn34p5+ajBeBrwzr6=NOHVs4hCa+k_uw=fA@mail.gmail.com> (raw)
In-Reply-To: <8c33aa3a-fde5-45ce-8f22-c817c6fa4a9a@crans.org>
On Tue, Jul 25, 2023 at 11:47 AM Johan Grande <nahoj@crans.org> wrote:
>
> I don't get it. What are the different patterns tried during this
> left-to-right evaluation of (|a*)~^(*b) ?
I'm going to invoke my "PWS may be able to explain some more" remark,
but basically once you cross the "~" it's no longer possible to
backtrack again; so it tries to match the empty alternative, gets an
empty result set, excludes ^(*b) from that result set leaving a
still-empty set, can't go back, and fails because the final result is
empty. I don't recall all the details but this has something to do
with X~Y implemented as "exclude Y from the result of X".
next prev parent reply other threads:[~2023-07-28 1:03 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-25 13:19 Johan Grande
2023-07-25 18:35 ` Bart Schaefer
2023-07-25 18:47 ` Johan Grande
2023-07-28 1:02 ` Bart Schaefer [this message]
2023-07-28 6:41 ` Stephane Chazelas
2023-07-29 1:35 ` Bart Schaefer
2023-08-01 13:19 ` Johan Grande
2023-08-01 13:30 ` Peter Stephenson
2023-08-01 13:46 ` Johan Grande
2023-08-02 8:31 ` Johan Grande
2023-08-02 9:37 ` Peter Stephenson
2023-07-31 11:36 ` Peter Stephenson
2023-07-31 15:21 ` Peter Stephenson
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