Affiliations: System Technology Division, Korea Institute of Science
and Technology, P.O. BOX 131, Cheongryang, Seoul, Korea. E-mail:
emmous@kist.re.kr | School of Computing, Queen's University, Kingston,
Ontario K7L 3N6, Canada. E-mail: ksalomaa@cs.queensu.ca | Department of Computer Science, The Hong Kong
University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR.
E-mail: dwood@cs.ust.hk
Abstract: Intercodes are a generalization of comma-free codes. Using the
structural properties of finite-state automata recognizing an intercode we
develop a polynomial-time algorithm for determining whether or not a given
regular language L is an intercode. If the answer is yes, our algorithm yields
also the smallest index k such that L is a k-intercode. Furthermore, we examine the prime intercode decomposition of
intercode regular languages and design an algorithm for the intercode primality
test of an intercode recognized by a finite-state automaton. We also propose an
algorithm that computes the prime intercode decomposition of an intercode
regular language in polynomial time. Finally, we demonstrate that the prime
intercode decomposition need not be unique.
Keywords: regular languages, finite-state automata, intercodes, state-pair graphs, prime decompositions
