Abstract

Lisp has a long history as a functional language, where action is invoked by calling a procedure, and where procedural abstraction and encapsulation provide convenient modularity boundaries. A number of attempts have been made to graft object-oriented programming into this framework without losing the essential character of Lisp—to include the benefits of data abstraction, extensible type classification, incremental operator definition, and code reuse through an inheritance hierarchy. CLOS—the Common Lisp Object System[2], which is an outcome of the ANSI standardization process for Common Lisp—represents a marriage of these two traditions. We explore the landscape in which the major object-oriented facilities exist, showing how the CLOS solution is effective within the two contexts. 1 Incremental Definition of Operations A generic function, or polymorphic function as it is sometimes called, is one whose implementation depends on the types of its arguments. That is, the code that is executed for a particular set of arguments is mechanically determined

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