From: Kornelius Kalnbach <murphy@...>
Date: 2009-02-06T03:28:16+09:00
Subject: [ruby-core:21868] Re: Regexp interpolation does not give equality

Shri Borde wrote:
> And equality of Regexps just looks at the regexp string, and does not
> try to do anything more fancy.
funny topic :) deciding whether two given regular expressions represent
the same language would be fancy indeed! Equivalence of NFAs is
co-NP-hard, and Ruby's regexps are much more complex...if they contain
CFL (do they? I think Oniguruma can count...), the problem is not even
decidable.

[murphy]