LISP and Symbolic Computation, 3(4)381-409
Conjunction-Type Standard ML PolymorphismR. Ghosh-Roy, Room Number 4B.526, Department of Computer Science, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, Essex, England, UK
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Abstract: It has been long argued that the well known Milner
type inference system implemented in the programming language Standard
ML is inadequate [4]. The arguments were presented on the basis of
intersection-type inference systems [3]. However no algorithm has been
developed. The intersection-type inference systems are closed under
r'-equality [1] and has been proved undecidable [7]. The paper
presents a new type inference system using conjunction-types which
extends the notion of intersection-types. The algorithm presented in
the author's previous paper [9] is easily adoptable into the Standard
ML. In this paper we shall discuss the features of the system and its
semantic soundness. Unlike the intersection-type inference systems,
the conjunction-type inference system is:
1. decidable 2. semantically sound for all types 3. semantically sound and complete for basic types. |
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