Custom Specializers in Object-Oriented Lisp

We describe in this paper the implementation and use of custom specializers in two current dialects of Lisp: Skill and Common Lisp. We motivate the need for such specializers by appealing to clarity of expression, referring to experience in existing industrial applications. We discuss the implementation details of such user-defined specializers in both dialects of Lisp, detailing open problems with those implementations, and we sketch ideas for solving them