Notes on typed object-oriented programming

Abstract

This paper, which is partly tutorial in nature, summarizes some basic research goals in the study and development of typed object-oriented programming languages. These include both immediate repairs to problems with existing languages and the long-term development of more flexible and expressive, yet type-safe, approaches to program organization and design. We summarize and compare three object models used in the theoretical literature. We also consider approaches to a few technical problems, including changes in the type of a method (member function) from super (base) class to sub (derived) class and the use of types that give information about the implementations as well as the interfaces of objects. Such implementation types seem essential for adequate typing of binary operations on objects, for example.