An Imperative Object Calculus
Martı́n Abadi, Luca Cardelli · Theory and Practice of Object Systems · 1995
We develop an imperative calculus of objects. Its main type constructor is the one for object types, which incorporate variance annotations and Self types. A subtyping relation between object types supports object subsumption. The type system for objects relies on unusual but beneficial assumptions about the possible subtypes of an object type. With the addition of polymorphism, the calculus can express classes and inheritance.