From: Artur Malabarba <bruce.connor.am@gmail.com>
To: David Kastrup <dak@gnu.org>
Cc: 20307@debbugs.gnu.org
Subject: bug#20307: 25.0.50; (regexp-opt nil ...) returns ""
Date: Mon, 13 Apr 2015 16:59:36 +0100 [thread overview]
Message-ID: <CAAdUY-Lx0uoaoA8kWaaq-MQmy6A4h17_eh8=hikvMyZD5qmknQ@mail.gmail.com> (raw)
In-Reply-To: <87iod0xcs5.fsf@fencepost.gnu.org>
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I believe you. Please ignore this babbling baboon.
That's what I get for typing on the bus.
On Apr 13, 2015 4:34 PM, "David Kastrup" <dak@gnu.org> wrote:
> Artur Malabarba <bruce.connor.am@gmail.com> writes:
>
> > 2015-04-12 10:50 GMT+01:00 David Kastrup
> >> Both
> >>
> >> M-: (regexp-opt nil) RET
> >>
> >> and
> >>
> >> M-: (regexp-opt nil t) RET
> >>
> >> return "". However, they should return a regexp matching nothing
> >> rather than everything, and the second invocation should also count as
> >> one () pairing.
> >
> > I agree there should be () on the second one, but I strongly disagree
> > they should match nothing.
> >
> > regexp-opt is NOT meant to match only the given strings. It is meant
> > to match anything containing the given strings.
>
> Well, and no string to match has been given. This is not
> (regexp-opt '(""))
> but rather
> (regexp-opt '())
>
> > There is a very fundamental difference in that. The less strings you
> > pass to regexp-opt, the MORE things the regexp will match.
>
> Come again?
>
> > Why would we suddently flip that on its head when going from 1 to 0
> > strings?
>
> (regexp-opt '("a" "b" "c")) -> "[abc]"
> (regexp-opt '("a" "b")) -> "[ab]"
>
> Quite literally (execute C-x C-e after the expressions above if you
> don't believe me). So how does "[ab]" match more than "[abc]" ?
>
> --
> David Kastrup
>
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next prev parent reply other threads:[~2015-04-13 15:59 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-12 9:50 bug#20307: 25.0.50; (regexp-opt nil ...) returns "" David Kastrup
2015-04-12 12:09 ` Stefan Monnier
2015-04-13 14:08 ` Artur Malabarba
2015-04-13 15:19 ` Stefan Monnier
2015-04-13 15:34 ` David Kastrup
2015-04-13 15:59 ` Artur Malabarba [this message]
2019-02-25 14:57 ` bug#20307: [PATCH] make regexp-opt return a no-match return value with empty input Mattias Engdegård
2019-03-02 12:37 ` Eli Zaretskii
2019-03-02 14:21 ` Mattias Engdegård
2019-03-02 14:41 ` Eli Zaretskii
2019-03-02 14:49 ` Mattias Engdegård
2019-03-02 14:57 ` Eli Zaretskii
2019-03-02 15:24 ` Mattias Engdegård
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