There's no regex that detects balanced parentheses, or is there? That is, search('and so ((x+y)+z) = (x+(y+z))') should return '((x+y)+z)'.
Not just a theoretical question, I'm cleaning up a large body of TeX code and a regex that did that would be very convenient. (Yes, I know it's not hard to detect balanced parentheses by hand...) I don't know that stuff, but I seen to recall reading that there's a theoretical notion of "regular expression" in CS, and a regular expression in that sense cannot do this. But in the same place I read that the actual regexes in programming languages include things which are not regular expressions in that theoretical sense. David C. Ullrich -- http://mail.python.org/mailman/listinfo/python-list