k-p-Infix codes and semaphore codes

In this paper we introduce the concepts of k-p-infix codes, n-k-ps-infix la nguages, n-k-infix-outfix codes, and n-k-prefix-suffix languages, which are natural generalizations of our previous work on k-prefix codes, k-infix co des and so on. We obtain several properties of k-p-intix codes and semaphor e codes. The relations and hierarchies of k-p-infix codes, n-k-ps-languages , and n-k-prefix-suffix languages, and their operations of these classes of languages are also investigated. (C) 2001 Elsevier Science B.V. All rights reserved.