Lazy List Comprehension in Logic Programming

The pure prolog evaluation of a goal yields a list of answers, but the tools provided for manipulating these structures are very poor. We discuss augmenting pure prolog with a list comprehension construct that offers the possibility of referring to the finite or infinite list of answers produced. Thus meta-predicates can be defined. A substructural calculus is used to give an axiomatic semantics to the extended language. Soundness and completeness of the intended evaluation with respect to this semantics is proved. 1. Introduction A well-known candidate for the use of a fragment of predicate logic as programming language is the logic of Horn clauses, usually regarded as the theoretical foundation of the programming language prolog. A set of Horn clauses can be viewed as a set of recursive definitions for predicates where the defining expressions are built using standard logical connectives. With respect to these predicates, goals are evaluated which may contain variables for which we ..