Why no RE match of A AND B?

[Anders J. Munch]

"Rene Pijlman" <reply.in at the.newsgroup> wrote:
> I take it this means:
>
>   match(r1&r2,s) <==> match(r1,s) and match(r2,s)
>
>
> I assume (without a formal prove at this point) that r1&r2 can
> always be reformulated as a simpler expression, BIMBW.

It can always be reformulated as an expression without an intersection
('&') operator.  But not necessarily a simpler one.

BIMBW?

I've never understood either why the intersection operator is usually
missing from regular expression implementations.  Tradition?

- Anders