Calculate the difference and intersection of any two regexes(phylactery.org)
325 points by posco | 108 comments
An interactive web tool that computes complement, intersection, difference, equivalence and DFAs for two entered regular expressions.
#regular-expressions on Hacker News
2 stories tagged regular-expressions, newest first.
A regular expression to check for prime numbers (2007)(noulakaz.net)
331 points by tambourine_man | 86 comments
A 2007 blog post explaining how the Perl regular expression /^1?$|^(11+?)\1+$/ checks whether a number is prime using unary representation.