Why no RE match of A AND B?

[Andrew Koenig]

jcm> I believe you're incorrect about this.  Regular languages are closed
jcm> over intersection.

I guess you're right -- you can always make a DFA with states that
consist of the cartesian product of the states of the operand machines.
But implementing it efficiently may be another matter.

-- 
Andrew Koenig, ark at research.att.com, http://www.research.att.com/info/ark