Regular languages are closed under intersection (as well as difference,

complement, and of course union).

I find myself needing to know whether two regexps intersect. That is,

whether the intersection of the two regexps is not empty.

I could code it up using the algorithm which can be found just about

anywhere regular language theory is sold, e.g.

http://www.cs.may.ie/~jpower/Courses/parsing/node13.html

But I wonder if there’s a better way to do this using ruby regular

expression tricks, or at least a way that is already coded up for me?