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arXiv · 1010.3263

Syntactic Complexity of Ideal and Closed Languages

Janusz Brzozowski·Yuli Ye
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Abstract

The state complexity of a regular language is the number of states in the minimal deterministic automaton accepting the language. The syntactic complexity of a regular language is the cardinality of its syntactic semigroup. The syntactic complexity of a subclass of regular languages is the worst-case syntactic complexity taken as a function of the state complexity $n$ of languages in that class. We study the syntactic complexity of the class of regular ideal languages and their complements, the closed languages. We prove that $n^{n-1}$ is a tight upper bound on the complexity of right ideals and prefix-closed languages, and that there exist left ideals and suffix-closed languages of syntactic complexity $n^{n-1}+n-1$, and two-sided ideals and factor-closed languages of syntactic complexity $n^{n-2}+(n-2)2^{n-2}+1$.

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Janusz Brzozowski, Yuli Ye. 2010-10-15. Syntactic Complexity of Ideal and Closed Languages. https://arxiv.org/abs/1010.3263

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