A simple technique for handling multiple polymorphism

Abstract

Certain situations arise in programming that lead to multiply polymorphic expressions, that is, expressions in which several terms may each be of variable type. In such situations, conventional object-oriented programming practice breaks down, leading to code which is not properly modular. This paper describes a simple approach to such problems which preserves all the benefits of good object-oriented programming style in the face of any degree of polymorphism. An example is given in Smalltalk-80 syntax, but the technique is relevant to all object-oriented languages.