Formal languages
Numeration systems, linear recurrences, and regular sets
Information and Computation
On a conjecture about slender context-free languages
Theoretical Computer Science
Discrete Applied Mathematics
Handbook of formal languages, vol. 1
Introduction To Automata Theory, Languages, And Computation
Introduction To Automata Theory, Languages, And Computation
On Subwords of Formal Languages
FCT '81 Proceedings of the 1981 International FCT-Conference on Fundamentals of Computation Theory
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Counting the number of distinct factors in the words of a language gives a measure of complexity for that language similar to the factor-complexity of infinite words. Similarly as for infinite words, we prove that this complexity function f(n) is either bounded or f(n)=n+1. We call languages with bounded complexity periodic and languages with complexity f(n)=n+1Sturmian. We describe the structure of periodic languages and characterize the Sturmian languages as the sets of factors of (one- or two-way) infinite Sturmian words.