OOPSLA'05 tutorial on generic functions and the CLOS Metaobject Protocol ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Town and Country Resort & Convention Center, San Diego, California Sunday, October 16, 2005, 13:30 - 17:00 See http://p-cos.net/oopsla05-tutorial.html

Abstract.

The Common Lisp Object System (CLOS) is unique in two ways.

+ In most OOP languages, methods belong to classes and are invoked by sending messages. In CLOS, methods belong to generic functions instead of classes, and those generic functions select and execute the correct method according to the types of the arguments they receive.

+ The CLOS Metaobject Protocol (MOP) specifies how its essential building blocks are to be implemented in CLOS itself. This allows extending its object model with metaclasses that change important aspects of CLOS for a well-defined scope.

This tutorial introduces these two notions. I will develop - live during the tutorial - the code for an interpreter for generic functions that performs selection and execution of methods. I will then discuss how that code can be extended to introduce, for example, multimethods and AOP-style advices, and sketch how generic functions are implemented efficiently in the "real" world. In the second part, I will illustrate the extensibility of the CLOS MOP by implementing - live - the (hashtable-based) Python object model as a metaclass. Other practical extensions based on the CLOS MOP are also sketched, like object-relational mappings, interfaces to foreign-language objects, and domain-specific annotations in classes.

The audience will learn about the basic concepts of generic functions and metaobject protocols. They will get the necessary insights and pointers to existing literature and online material to deepen their knowledge. The focus of the tutorial is not on technical details but on the general ideas. A good understanding of class-based OOP is required. Experience with Lisp may be helpful, but the tutorial is specifically targeted at non-Lispers.

Feel free to contact me if you have any questions and/or suggestions.

Pascal