Metaphoric polymorphism: Taking code reuse one step further

Abstract

We propose two new constructs for object oriented programming that significantly increase polymorphism. Consequently, code may be reused in ways unaccounted for by existing machinery. These constructs of type correspondence and partial inheritance are motivated from metaphors of natural language and thought. They establish correspondences between types non of which is (necessarily) a subtype of the other. As a result, methods may operate on objects — and may receive arguments — of types different than the ones originally intended for. The semantics of the proposed constructs generalizes that of ordinary inheritance, thereby establishing the latter as a special case. We show that the incorporation of these constructs in programming supports the process of natural software evolution and contributes to a better conceptual organization of the type system.