Logic Meta-Programming Facilities in 'LOG

A meta-level extension of a logic programming language is presented. The resulting language, called 'LOG (read quote-log), provides meta-programming facilities similar to those of Prolog while preserving a declarative logical semantics. It also offers new meta-programming opportunities as compared with Prolog due to its ability to treat whole programs, i.e. sequences of clauses, as data objects. The extension basically consists in defining a suitable naming scheme. It associates two different but related meta-representations with every syntactic object of the language, from characters to programs. The choice of the double meta-representation is motivated by both the user and the implementation viewpoints. All Prolog built-in meta-predicates can be redefined as 'LOG programs by exploiting the new naming scheme. Then some syntactic sugar is added to make the language more concrete. Some examples are given, in particular to show the ability of the language to deal with programs as data.