A Portable Prolog Predicate for Printing Rational Terms

ABSTRACT. Rational terms or rational trees are terms with one or more infinite sub-terms but with a finite representation. Rational terms appeared as a side effect of omitting the \emph{occurs check} in the unification of terms, but its support across Prolog systems varies and often fails to provide the expected functionality. A common problem is the lack of support for printing query bindings with rational terms. In this paper, we discuss the minimum requirements a Prolog system should have to support printing rational terms and propose the integration of an ISO Prolog predicate that works in several existing Prolog systems in order to overcome the technical problem of printing rational terms. This predicate could be easily adapted to work both for the top query printouts and for user printing.