That doesn't bother me. The OP seemed to be discussing the validity and practicality of single-entry character classes. And I believe he was discussing them in the context of the [....] operator in a regexp. The backslash CC's and property CC's are already 'single entry', so probably not really so relevant to the discussion, particularly where they can stand-alone outside of a user-defined character class.

Certainly the POSIX classes constitute "single entries". And that's definitely another good argument for why single-entry character classes are practical, and should be legal (which, of course, they are).

The negated character class of a single entry just happened to be the first example that jumped to my mind. Your POSIX thought is great too.

Thanks for your response, as I was trying to clarify, to self, just what makes a "single entry class". I was thinking strictly of a character class without any meta characters.

davido and pary, thanks. davido you're correct...I was checking not so much on the validity of a single entry class (I know it's legal). I was just curious about why a programmer might want to have a single character class. pary made me think and realize, much like you're note of the negated class, that there are meta-character situations where a single entry could be usefule, too.

Thanks to you both. I appreciate your insights.

ack Albuquerque, NM