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.