Title

New Theoretical and Computational Results for Regular Languages

Abstract

We show how to turn a regular expression into an O(s) space representation of McNaughton and Yamada's NFA, where s is the number of NFA states. The standard adjacency list representation of McNaughton and Yamada's NFA takes up s+s 2 space in the worst case. The adjacency list representation of the NFA produced by Thompson takes up between 2r and 5r space, where r s in general, and can be arbitrarily larger than s. Given any set T of NFA states, our representation can be used to compute the set N of states one transition away from the states in T in optimal time O(jT j + jN j). McNaughton and Yamada's NFA requires \Theta(jT j \Theta jN j) in the worst case. Using Thompson's NFA, the equivalent calculation requires \Theta(r) time in the worst case. An implementation of our NFA representation confirms that it takes up an order of magnitude less space than McNaughton and Yamada's machine. An implementation to produce a DFA from our NFA representation by subset construction sho...

Department(s)

Mathematics and Statistics

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1991 New York University, All rights reserved.

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