An implementation of narrowing

Abstract

In this paper we discuss implementation issues of rite, a system that performs lazy narrowing and eager rewriting with respect to a set of directed equations. We describe a novel technique for representing the multiple solutions that arise from the enumerative nondeterminism of narrowing steps. A technique for efficiently identifying redexes, based on the preprocessing of equations for partial matches/unifiers, is presented. Rewriting and narrowing are effected through demons which annotate subterms with continuations obtained from preprocessing. We show how these methods can be extended to deal with conditional equations viewed as logic programs. An experimental implementation is discussed.