摘要:Let A X* be a regular language. In the paper, we will provide an algorithm to decide whether there exist a nontrivial language B (n, X) and a nontrivial regular language C X* such that A = B C 1.) C. S. Calude, K. Salomaa, S. Yu (eds.). Advances and Trends in Automata and Formal Languages. A Collection of Papers in Honour of the 60th Birthday of Helmut Jürgensen.