Generalizations of Code Languages with Marginal Errors

We study k-prefix-free, k-suffix-free and k-infix-free languages that generalize prefix-free, suffix-free and infix-free languages by allowing marginal errors. For example, a string x in a k-prefix-free language L can be a prefix of up to k different strings in L. Namely, a code (language) can allow some marginal errors. We also define finitely prefix-free languages in which a string x can be a prefix of finitely many strings. We present efficient algorithms that determine whether or not a given regular language is k-prefix-free, k-suffix-free or k-infix-free, and analyze their runtime. Lastly, we establish the undecidability results for (linear) context-free languages.