Foundations of Object-Oriented Languages: Types and Semantics

In recent years, object-oriented programming has emerged as the dominant computerprogramming style, and object-oriented languages such as C++ and Java enjoy wide use in academia andindustry. This text explores the formal underpinnings of object-oriented languages to help thereader understand the fundamental concepts of these languages and the design decisions behindthem.The text begins by analyzing existing object-oriented languages, paying special attention totheir type systems and impediments to expressiveness. It then examines two key features: subtypesand subclasses. After a brief introduction to the lambda calculus, it presents a prototypicalobject-oriented language, SOOL, with a simple type system similar to those of class-basedobject-oriented languages in common use. The text offers proof that the type system is sound byshowing that the semantics preserves typing information. It concludes with a discussion of desirablefeatures, such as parametric polymorphism and a MyType construct, that are not yet included in moststatically typed object-oriented languages.

Kim B. Bruce is Frederick Latimer Wells Professor of Computer Science at Williams College.