QUOTIENT COMPLEXITY OF STAR-FREE LANGUAGES.

The quotient complexity, also known as state complexity, of a regular language is the number of distinct left quotients of the language. The quotient complexity of an operation is the maximal quotient complexity of the language resulting from the operation, as a function of the quotient complexities of the operands. The class of star-free languages is the smallest class containing the finite languages and closed under boolean operations and concatenation. We prove that the tight bounds on the quotient complexities of union, intersection, difference, symmetric difference, concatenation and star for starfree languages are the same as those for regular languages, with some small exceptions, whereas Zⁿ -- 1 is a lower bound for reversal. [ABSTRACT FROM AUTHOR]