QUALIFIED TYPES: THEORY AND PRACTICE

Abstract

This thesis describes a type system that combines ML-style polymorphism with a general approach to overloading. The central idea is to use qualified types that include predicates and restrict the set of types at which an object can be used to particular instances of a polymorphic type. Different applications of qualified types can be obtained by changing the underlying system of predicates. We illustrate this with examples including type classes, explicit subtyping and extensible records.