Abstract

Genericity allows the substitution of types in a class. This is usually obtained through parameterized classes, although they are inflexible since any class can be inherited but is not in itself parameterized. We suggest a new genericity mechanism, type substitution, which is a subclassing concept that complements inheritance: any class is generic, can be "instantiated" gradually without planning, and has all of its generic instances as subclasses. 1 Introduction This paper proposes type substitution as a new genericity mechanism for statically typed object-oriented languages. With this concept we avoid type variables and second-order entities and obtain the natural complement of inheritance; both are subclassing mechanisms and they differ as follows. ffl Inheritance. Construction of subclasses by adding variables and procedures, and by replacing procedure bodies. ffl Type substitution. Construction of subclasses by substituting types. Type substitution is supportive of the real-li...

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