  It is known that an ordinal is the order type of the lexicographic ordering
of a regular language if and only if it is less than omega^omega. We design a
polynomial time algorithm that constructs, for each well-ordered regular
language L with respect to the lexicographic ordering, given by a deterministic
finite automaton, the Cantor Normal Form of its order type. It follows that
there is a polynomial time algorithm to decide whether two deterministic finite
automata accepting well-ordered regular languages accept isomorphic languages.
We also give estimates on the size of the smallest automaton representing an
ordinal less than omega^omega, together with an algorithm that translates each
such ordinal to an automaton.
