Narrowing extends rewriting with logic capabilities by allowing logic variables in terms and replacing matching with unification. Narrowing has been widely used in different contexts, ranging from theorem proving (e.g., protocol verification) to language design (e.g., it forms the basis of functional logic languages). Surprisingly, the termination of narrowing has been mostly overlooked. In this paper, we present a new approach for analyzing the termination of narrowing in left-linear constructor systems—a widely accepted class of systems—that allows us to reuse existing methods in the literature on termination of rewriting.

Partial evaluation is a well-known technique for program specialization [4]. Essentially, given a program and part of its input data—the so-called static data—a partial evaluator returns a new, residual program which is specialized for the given data. The residual program is then used for performing the remaining

Partial evaluation [10] aims at specializing programs w.r.t. part of their input data (the static data). Partial evaluation may proceed either online or offline. Online techniques implement a single, monolithic procedure that specializes the program while dynamically checking that the termination of the process is kept.