Re: Intersection of regular expression languages

haberg@math.su.se (Hans Aberg) writes:


> Can the intersection of two regular expression languages be
> constructed as a regular expression language?


I'm going to say something which I hope isn't stupid in response to
this. The class of regular languages forms a Boolean algebra with
respect to the union and intersection operators, which I believe means
that they also form a field with those operators, which means they are
closed with respect to both of them. I believe one can even use the
class of regular languages as a topology.


So, in case, this is a homework problem (since it is a commonly asked
hw problem in automata theory). Identify what the identity languages
are for the two operators. Show that idempotence holds. Find the
union and intersection inverses of a given language. Is there
something interesting about the two inverses? Does DeMorgan's theorem
hold?


Hope this helps,
-Chris


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Chris Clark Internet : compres@world.std.com
Compiler Resources, Inc. Web Site : http://world.std.com/~compres
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