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Re: Regexp notation

To: scsh@martigny.ai.mit.edu
Subject: Re: Regexp notation
From: shivers@ai.mit.edu (Olin Shivers)
Date: 10 Jan 1997 09:48:30 -0500
Organization: Artificial Intelligence Lab, MIT
Reply-to: shivers@ai.mit.edu
Thank you for your input, Mike. I was hoping an implementor like you would
comment on the issues.

I came to Kelvin's conclusions on my own last night, namely

    - Complement means just complementing accept/non-accept states
      in the NDFA. No blowup in NDFA space at all. How this affects
      state count in the result DFA compared to the original DFA, 
      I don't know.

    - Intersection means taking the cross-product of the NDFA's state
      space. This is blowup. Is it significant in practice?

This doesn't seem too horrible. So what's the problem?

One thing seems clear -- to do intersection and complement, we'd have
to extend the interface to the underlying matching engine.
    -Olin

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