From Monomorphic to Polymorphic Well-Typings and Beyond

Abstract. Type information has many applications; it can e.g. be used in optimized compilation, termination analysis and error detection. How-ever, logic programs are typically untyped. A well-typed program has the property that it behaves identically on well-typed goals with or without type checking. Hence the automatic inference of a well-typing is worth-while. Existing inferences are either cheap and inaccurate, or accurate and expensive. By giving up the requirement that all calls to a predicate have types that are instances of a unique polymorphic type but instead allowing multiple polymorphic typings for the same predicate, we ob-tain a novel strongly-connected-component-based analysis that provides a good compromise between accuracy and computational cost.