Modules for Prolog Revisited

Abstract

Abstract. Module systems are an essential feature of programming languages as they facilitate the re-use of existing code and the development of general purpose libraries. Unfortunately, there has been no consensual module system for Prolog, hence no strong development of libraries, in sharp contrast to what exists in Java for instance. One difficulty comes from the call predicate which interferes with the protection of the code, an essential task of a module system. By distinguishing the called module code protection from the calling module code protection, we review the existing syntactic module systems for Prolog. We show that no module system ensures both forms of code protection, with the noticeable exceptions of Ciao-Prolog and XSB. We then present a formal module system for logic programs with calls and closures, define its operational semantics and formally prove the code protection property. Interestingly, we also provide an equivalent logical semantics of modular logic programs without calls nor closures, which shows how they can be translated into constraint logic programs over a simple module constraint system.

Closures and Modules Within Linear Logic Concurrent Constraint Programming

“…These results have been illustrated with an instantiation of the MLCC scheme to constraint logic programs, leading to a simple yet powerful module system similar to the one proposed in [10], supporting code hiding, closures and module parameterization, and provided here with a simple logical semantics in linear logic. Another interesting use is the boostrapping of a complete implementation of LCC that is currently under development [9].…”

“…This module system is an extension including dynamic modules of the module system proposed for CLP in [10]. It is provided here with a logical semantics in linear logic, and with an implementation with closures in the line of its semantics in LCC.…”

“…This module system is then illustrated in Sect. 4, by its instantiation to constraint logic programming (CLP) languages, and by its relationship to the module system proposed in [10]. Its implementation is discussed there along the lines of its semantics in LCC, and is illustrated with examples of code hiding, closure programming and module parameterization in CLP.…”

From Rules to Constraint Programs with the Rules2CP Modelling Language

“…In order to avoid name clashes in declaration and rule heads, the language includes a simple module system that prefixes names with module and package names, similarly to [8]. A head is formed with an ident with distinct variables as arguments.…”

“…Lists are formed without a binary list constructor, by enumerating all their elements, or intervals of values in the case of integers. For instance [1,3..6,8] represents the list [1,3,4,5,6,8]. Such lists are used to represent the domains of variables in (var in list) formula, and in the answers returned to Rules2CP goals.…”