The unsolvability of the equivalence problem for e-free NGSM's with unary input (output) alphabet and applications

Authors:
Oscar H. Ibarra
Affiliations:
-
Venue:
SFCS '77 Proceedings of the 18th Annual Symposium on Foundations of Computer Science
Year:
1977

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Cited 1

Sigma*: symbolic learning of input-output specifications

POPL '13 Proceedings of the 40th annual ACM SIGPLAN-SIGACT symposium on Principles of programming languages

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Abstract

It is shown that the equivalence problem is unsolvable for ε-free nondeterministic generalized sequential machines whose input/output are restricted to unary/binary (binary/unary) alphabets. This strengthens a known result of Griffiths. Applications to some decision problems concerning right-linear grammars and directed graphs are also given.