Technical Reports (CIS)

Document Type

Technical Report

Date of this Version

August 1990


University of Pennsylvania Department of Computer and Information Science Technical Report No. MS-CIS-90-54.


It has been argued elsewhere that a logic programming language with function variables and λ-abstractions within terms makes a good meta-programming language, especially when an object-language contains notions of bound variables and scope. The λProlog logic programming language and the related Elf and Isabelle systems provide meta-programs with both function .variables and λ-abstractions by containing implementations of higher-order unification. This paper presents a logic programming language, called , that also contains both function variables and λ-abstractions, although certain restrictions are placed on occurrences of function variables. As a result of these restrictions, an implementation of does not need to implement full higher order unification. Instead, an extension to first-order unification that respects bound variable names and scopes is all that is required. Such unification problems are shown to be decidable and to possess most general unifiers when unifiers exist. A unification algorithm and logic programming interpreter are described and proved correct. Several examples of using as a meta-programming language are presented.



Date Posted: 24 August 2007