Abstract

During the execution of functional logic programs, E-unification problems have to be solved quite frequently, where the underlying equational theory is induced by recursive functions. But, what about the decidability of those E-unification problems? Up to now, there does not exist a concrete answer to this question for classes of equational theories which are induced by particular recursive functions. In this paper, we try to give an answer to this question by drawing and verifying a strict border between undecidability and decidability of E-unification problems for particular classes of recursive functions. Since this result shows that the E-unification problem is undecidable even for a very restricted class of recursive functions, the nondeterministic implementations of those problems in functional logic programming languages are justified.

Citations