Why no RE match of A AND B?

[Rene Pijlman]

Erik Max Francis:
>"Anders J. Munch" wrote:
>> I've never understood either why the intersection operator is usually
>> missing from regular expression implementations.  Tradition?
>
>Probably for the reason you mention:  It can easily be reexpressed as
>another regular expression, whether simpler or more complicated.  That
>isn't true in general, for, say, the | regular expression operator

But OTOH there are notational shortcuts in the usual RE
languages. For example:

   a+ == aa*
   r{3,5} == rrrr?r?

So what makes the intersection different?

-- 
René Pijlman