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in reply to The craziest RegExes you ever created

Mine was implementing negative lookaround assertions with plain grep -E. I did it for detecting cross-posts between certain newsgroups. The precise regex I used was anchored to the beginning of the line:

^([^e]|e([^s]|s([^\.]|\.([^c]|c([^o]|o([^m]|m([^p]|p([^\.]|\.([^o]|o([^s]|s([^\.]|\.([^l]|l([^i]|i([^n]|n([^u]|u[^x])))))))))))))))

I even made some pseudo-algorithm for building more:

^ ([^e]|e ([^s]|s ([^\.]|\. ([^c]|c <blah> ([^n]|n ([^u]|u [^x] )))))))))))))))

But didn't bother to automate it. In fact, I've never used this again.

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David Serrano