Abstract

We introduce an extension of the intersection type discipline in which types may contain variables with upper and lower bounds, present an algorithm for deciding the subtype relation in the extended system, and prove that the algorithm is correct. This work was supported in part by the Office of Naval Research and the Defense Advanced Research Projects Agency (DOD) under contract number N00014-84-K-0415. The views and conclusions contained in this document are those of the author and should not be interpreted as representing the official policies, either expressed or implied, of DARPA or the U.S. Government. 1 INTRODUCTION 1 1 Introduction The intersection type discipline [?] is a simple, yet powerful language for describing the behavior of programs. Beyond its intrinsic theoretical interest [?, ?], it appears to be an attractive foundation for the type systems of practical programming languages [?, ?]. Although the usual formulations do not allow quantification over types---there ...

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