Re: [FWP] japhy had a silly idea...

[Jeff Pinyan <jeffp@crusoe.net>]

On May 25, Ilmari Karonen said:

>On Fri, 25 May 2001, Jeff Pinyan wrote:
>> I tried for an hour and a half or so to craft a regex that matches itself,
>> and ONLY itself.
>> 
>> I came up with nothing -- well, several dead ends at least.
>
>What are the constraints?  If embedding Perl code is allowed, I'd say
>the problem essentially reduces to constructing a quine.
>
>(No, I don't have the time to attempt a solution just now..)

Indeed, I did solve it, using (??{ ... }).  Once I realized I could use
that, it was trivial.

  123456789_123456789_123456789_123456789_1234567 = 47
  ^.*(??{$&ne'^.*(??{'.substr($&,7,-4).'})\z'})\z

-- 
Jeff "japhy" Pinyan      japhy@pobox.com      http://www.pobox.com/~japhy/
Are you a Monk?  http://www.perlmonks.com/     http://forums.perlguru.com/
Perl Programmer at RiskMetrics Group, Inc.     http://www.riskmetrics.com/
Acacia Fraternity, Rensselaer Chapter.         Brother #734
** I need a publisher for my book "Learning Perl's Regular Expressions" **


==== Want to unsubscribe from Fun With Perl?  Well, if you insist...
==== Send email to <fwp-request@technofile.org> with message _body_
====   unsubscribe