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Revision: 6788
at June 14, 2008 11:08 by banzaiman
Updated Code 
^1?$|^(11+?)\1+$

Revision: 6787
at June 14, 2008 11:07 by banzaiman
Updated Code 
/^1?$|^(11+?)\1+$/

Revision: 6786
at June 14, 2008 11:02 by banzaiman
Initial Code 
print "Prime" if (1 x shift) !~ /^1?$|^(11+?)\1+$/
Initial URL 

                                

                                                            

                                    

                                        

                                        Initial Description
                                        

                                    

                                    
By the legendary abigail.  Fails to match if and only if it is matched against a prime number of 1's.  That is, '11' fails, but '1111' does not.

I once heard him talk why this works, but I forgot most of it.

                                

                                                            

                                    

                                        

                                        Initial Title
                                        

                                    

                                    
Prime number tester

                                

                                                            

                                    

                                        

                                        Initial Tags
                                        

                                    

                                    
regex

                                

                                                            

                                    

                                        

                                        Initial Language
                                        

                                    

                                    
Regular Expression