Implementation of a Deterministic Partial E-Unification Algorithm for Macro Tree Transducers

Abstract

During the execution of functional logic programs particular E uni cation pro blems have to be solved quite frequently In this paper we contribute to the e cient solution of such problems in the case where E is induced by particular term rewriting systems called macro tree transducers We formalize the implementation of a deter ministic partial E uni cation algorithm on a deterministic abstract machine called twin uni cation machine The uni cation algorithm is based on a particular narrow ing strategy which combines leftmost outermost narrowing with a local constructor consistency check and a particular occur check The twin uni cation machine uses two runtime stacks it is an extension of an e cient leftmost outermost reduction machine for macro tree transducers The feasibility of the presented implementation technique is proved by an implementation which has been developed on a SPARCstation SLC The work of the authors are supported by the Deutsche Forschungsgemeinschaft DFG