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#### Quotient Complexity of Bifix-, Factor-, and Subword-Free Regular Language

(Institute of Informatics: University of Szeged, 2014)

A language $L$ is prefix-free if whenever words $u$ and $v$ are in $L$ and $u$ is a prefix of $v$, then $u=v$. Suffix-, factor-, and subword-free languages are defined similarly, where by ``subword" we mean ``subsequence", ...

#### Quotient Complexities of Atoms in Regular Ideal Languages

(Institute of Informatics: University of Szeged, 2015)

A (left) quotient of a language L by a word w is the language w(-1) L = {x vertical bar wx is an element of L}. The quotient complexity of a regular language L is the number of quotients of L; it is equal to the state ...

#### Complexity of Right-Ideal, Prefix-Closed, and Prefix-Free Regular Languages

(Institute of Informatics: University of Szeged, 2017)

A language L over an alphabet E is prefix-convex if, for any words x, y, z is an element of Sigma*, whenever x and xyz are in L, then so is xy. Prefix-convex languages include right-ideal, prefix-closed, and prefix-free ...

#### Quotient Complexity of Ideal Languages

(Elsevier, 2013-01-28)

A language L over an alphabet Σ is a right (left) ideal if it satisfies L=LΣ∗ (L=Σ∗L). It is a two-sided ideal if L=Σ∗LΣ∗, and an all-sided ideal if L=Σ∗L, the shuffle of Σ∗ with L. Ideal languages are not only of interest ...

#### Most Complex Regular Ideal Languages

(Discrete Mathematics and Theoretical Computer Science, 2016-10-17)

A right ideal (left ideal, two-sided ideal) is a non-empty language $L$ over an alphabet $\Sigma$ such that $L=L\Sigma^*$ ($L=\Sigma^*L$, $L=\Sigma^*L\Sigma^*$). Let $k=3$ for right ideals, 4 for left ideals and 5 for ...

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

(Otto-von-Guericke-Universit¨at Magdeburg, 2012)

The syntactic complexity of a regular language is the cardinality of its syntactic semi-group. The syntactic complexity of a subclass of regular languages is the maximal syntactic complexity of languages in that subclass, ...

#### 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 ...

#### 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 ...

#### 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 ...

#### Syntactic Complexity of Suffix-Free Languages

(Elsevier, 2017-09-05)

We solve an open problem concerning syntactic complexity: We prove that the cardinality of the syntactic semigroup of a suffix-free language with n left quotients (that is, with state complexity n) is at most (n−1)n−2+n−2 ...