December 30, 2010

A non-hierarchical approach to object-oriented programming

The Lisp historical archive web site just got reorganized. I have made a quick check of the contents, and found out that Howard I. Cannon's original technical report about Flavors - A non-hierarchical approach to object-oriented programming was finally made available as part of that archive. The report was originally written in 1979, was circulated around Lispers, but was never ever published as an actual technical report, although it is cited as such in several later papers by other authors. It describes the original object-oriented extension to the MIT Lisp Machine, heavily influenced by Smalltalk, but with multiple inheritance and method combinations added (but no multiple dispatch yet, which got only introduced in CommonLoops, a direct predecessor of CLOS). Although unpublished and clearly in an unfinished state, this report itself influenced a lot of other subsequent experiments with object-oriented extensions to Lisp dialects. Among other things, it already mentions the idea of exploring "meta-protocols" for making parts of the implementation of the object-oriented extension itself customizable, which was later investigated in much more detail as part of the work on the CLOS MOP (see also The Art of the Metaobject Protocol). And, of course, method combinations were already a very early predecessor of aspect-oriented programming.

It's good that this very important historical document is finally available!

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