Formal languages
Results concerning palindromicity
Journal of Information Processing and Cybernetics
New Decidability Results Concerning Two-Way Counter Machines
SIAM Journal on Computing
Handbook of formal languages, vol. 1
Undecidability in integer weighted finite automata
Fundamenta Informaticae - Special issue dedicated to A. Salomaa
Journal of the ACM (JACM)
Reversal-Bounded Multicounter Machines and Their Decision Problems
Journal of the ACM (JACM)
L(A) = L(B)? decidability results from complete formal systems
Theoretical Computer Science
Decidability of DPDA equivalence
Theoretical Computer Science
Introduction to Formal Language Theory
Introduction to Formal Language Theory
The Commutation of Finite Sets: a Challenging Problem
The Commutation of Finite Sets: a Challenging Problem
Debugging and verification of infinite state real-time systems
Debugging and verification of infinite state real-time systems
The Mathematical Theory of Context-Free Languages
The Mathematical Theory of Context-Free Languages
FCT '01 Proceedings of the 13th International Symposium on Fundamentals of Computation Theory
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Let e be a class of automata (in a precise sense to be defined) and ec the class obtained by augmenting each automaton in e with finitely many reversal-bounded counters. We first show that if the languages defined by e are effectively semilinear, then so are the languages defined by ec, and, hence, their emptiness problem is decidable. This result is then used to show the decidability of various problems concerning morphisms and commutation of languages. We also prove a surprising undecidability result: given a fixed two element code K, it is undecidable whether a given context-free language L commutes with K, i.e., LK = KL.