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#### Complexity of Proper Prefix-Convex Regular Languages

(Springer, 2017-06-27)

A language L over an alphabet Σ is prefix-convex if, for any words x,y,z∈Σ∗, whenever x and xyz are in L, then so is xy. Prefix-convex languages include right-ideal, prefix-closed, and prefix-free languages, which were ...

#### Complexity of Left-Ideal, Suffix-Closed and Suffix-Free Regular Languages

(Springer, 2017-03-06)

A language L over an alphabet Σ is suffix-convex if, for any words x,y,z∈Σ∗, whenever z and xyz are in L, then so is yz. Suffix-convex languages include three special cases: left-ideal, suffix-closed, and suffix-free ...

#### Most Complex Non-returning Regular Languages

(Springer, 2017-07-03)

A regular language L is non-returning if in the minimal deterministic finite automaton accepting it there are no transitions into the initial state. Eom, Han and Jirásková derived upper bounds on the state complexity of ...

#### Unrestricted State Complexity Of Binary Operations On Regular And Ideal Languages

(Institut für Informatik, 2017-08-27)

We study the state complexity of binary operations on regular languages over diﬀerent alphabets. It is known that if L′m and Ln are languages of state complexities m and n, respectively, and restricted to the same alphabet, ...

#### Syntactic Complexities of Some Classes of Star-Free Languages

(Springer, 2012)

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 maximal syntactic complexity of languages in that subclass, ...

#### Large Aperiodic Semigroups

(World Scientific Publishing, 2015-11-01)

We search for the largest syntactic semigroups of star-free languages having n left quotients; equivalently, we look for the largest transition semigroups of aperiodic finite automata with n states. We first introduce ...

#### Most Complex Regular Right-Ideal Languages

(Springer, 2014)

A right ideal is a language L over an alphabet Sigma that satisfies the equation L = L Sigma*. We show that there exists a sequence (Rn vertical bar n >= 3) of regular right-ideal languages, where R-n has n left quotients ...