Metaclasses are first class: The ObjVlisp Model

Abstract

This paper shows how an attempt at a uniform and reflective definition resulted in an open-ended system supporting ObjVlisp, which we use to simulate object-oriented language extensions.We propose to unify Smalltalk classes and their terminal instances. This unification allows us to treat a class as a "first class citizen", to give a circular definition of the first metaclass, to access to the metaclass level and finally to control the instantiation link. Because each object is an instance of another one and because a metaclass is a real class inheriting from another one, the metaclass links can be created indefinitely.This uniformity allows us to define the class variables at the metalevel thus suppressing the Smalltalkambiguity between class variables and instance variables: in our model the instance variables of a class are the class variables of its instances.

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