From: Hans Aberg (haberg@math.su.se)
Date: Tue Oct 09 2007 - 20:04:59 CDT
On 10 Oct 2007, at 01:11, Philippe Verdy wrote:
> Anyway, you're still not replying to the question: which is the
> expected
> ordering for the returned matches?
If you know what language the grammar produces, then you know the
language complement. And the DFA construct shows that if the grammar
is RE (Chomsky hierarchy type 3), there exists an RE grammar that
produces the complement language.
> I absolutely don't care if you use a DFA or not.
So once you have decided what the abstract symbols you use in your RE-
like algebra should mean grammar-wise (hopefully producing an RE
grammar), or what DFA they should produce, you can use your favorite
method to compute an RE grammar that produces the language complement.
I do not know why this complement operation is important, though.
Hans Åberg
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