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

@article{Ibarra1977TheUO,
  title={The unsolvability of the equivalence problem for e-free NGSM's with unary input (output) alphabet and applications},
  author={Oscar H. Ibarra},
  journal={18th Annual Symposium on Foundations of Computer Science (sfcs 1977)},
  year={1977},
  pages={74-81}
}
  • Oscar H. Ibarra
  • Published 1977 in
    18th Annual Symposium on Foundations of Computer…
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.