regex - Regular expression for finding a regular expression?

Question

Does anyone have code for finding a file that contains a regular expression? I would assume you could have two different flavors, one for BREs and one for EREs.

You would think some kind of test suites would have something like an isRegex() test. Can anyone have any code? Looking for something comprehensive of course.

I see this was discussed here but didn't see any practical responses. If I want to grep for any file that contains a regular expression, perhaps bounded by the typical //, how would I do it?

Answer 1

Regular expressions are themselves not a regular language. The clue is that they contain parentheses and square brackets and such that must be balanced.

A regular expression itself can be described by a context-free grammar, and parsed with a recursive-descent parser.