From: Xavier Noria <fxn@...>
Date: 2008-04-01T17:17:15+09:00
Subject: Re: Primes in P?

On Apr 1, 2008, at 4:23 , Charles Zheng wrote:

>>     ((("1" * self) =~ /^1$|^(11+?)\1+$/) == nil)
>>   end
>> end
> ...
>> The turnaround time on solving is almost instantaneous for this
>> algorithm until the numbers start gets really big (i.e. like the  
>> 123457
>> above).  I don't know if this matches the criteria for "polynomial
>> running time" but thought you might find this interesting if you  
>> didn't
>> know about it.
>> Michael
>
> That is pretty cool. It is not of polynomial running time since it  
> tries
> to factor the number brute-force, but that is a very nifty reg EXP
> trick.

The author is Perl hacker Abigail, it first appeared in  
comp.lang.perl.misc:

-- fxn