SPUG: minimal unmatching regex

[Ingy dot Net]

On Tue, Aug 18, 2009 at 10:33 PM, Steve Sandvik <ssandv at gmail.com> wrote:

> well, /$^/ seems like a plausible starting point.  Or ending point.
> Or something. :-)


Nope.

    $^ = "";
    $anything =~ /$^/;



>
>
> Steve Sandvik
>
> On Tue, Aug 18, 2009 at 12:04 PM, Michael R. Wolf<MichaelRWolf at att.net>
> wrote:
> > Question:
> > What's the smallest (comprehensible) regex that's guaranteed to fail
> against
> > all input?
> >
> > Motivation:
> > I'm creating a lab for perl classes.  I want to provide the stub of a
> script
> > that compiles, but always fails to match.  Unfortunately, the obvious
> > minimal RE of // matches *everything*.
> >
> > Here's a stub of the lab...
> >
> > # TODO... replace the following line with your regular expression to
> match
> > zip codes.
> > my $zip_re = qr//;
> >
> > like('98107', $zip_re, 'Simple 5-digit zip'),
> > like('07748', $zip_re, 'Simple 5-digit zip with leading zero'),
> >
> > unlike('1234',          $zip_re, 'Four digits');
> > unlike('123456',        $zip_re, 'Six digits');
> >
> > --
> > Michael R. Wolf
> >    All mammals learn by playing!
> >        MichaelRWolf at att.net
> >
> >
> >
> >
> > _____________________________________________________________
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> >
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>
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