Print Page - Funny regexp: /^1?$|^(11+?)\1+$/

Title: Funny regexp: /^1?$|^(11+?)\1+$/
Post by: Cyril on October 06, 2010, 06:08:31 PM

I have found this funny regexp here (//http), guess what it matches? Or check it with newLISP:

Code Select Expand
(for (i 1 100)
  (unless (regex {^1?$|^(11+?)1+$} (dup "1" i))
    (print i " ")))

Astonishing! ;-)

Title: Re: Funny regexp: /^1?$|^(11+?)\1+$/
Post by: cormullion on October 07, 2010, 10:19:26 AM

Cool. Someone explain it to me ... :/

Title: Re: Funny regexp: /^1?$|^(11+?)\1+$/
Post by: Lutz on October 07, 2010, 02:17:49 PM

There is a nice explanation here:

http://zmievski.org/2010/08/the-prime-that-wasnt

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