Common Lisp Object System

https://en.wikipedia.org/wiki/Common_Lisp_Object_System

Besides Google, I find Wikipedia is often helpful when finding acronym definitions as well. In this particular case, probably adding "Lisp" to your Google search would have helped, but if you didn't know it was limited to that domain, it's understandable that you didn't include it.

CLOS is--IMHO--the most advanced object system ever invented. The freedom that comes from CLOS is mind-blowing. Learning what CLOS can do will make you hate every other object-oriented programming system.

I think BETA comes close, but it never made it into mainstream.

Very true. And the most mind blowing thing? CLOS is implemented in Lisp itself using macros. So as a Lisp user, you are able to extend the language to include the best implementation of any particular paradigm that exists.

> CLOS is implemented in Lisp itself using macros.

This is a persistent myth. CLOS is built in to the language.

Somehow.

The original first CLOS implementation called PCL (Portable CommonLoops) was written in 100% Common Lisp with very little implementation specific CL code. PCL was a library which ran on at least 15 different Common Lisp implementations.

What really is a myth that it's (only) macros. That CLOS implementation is a complex library written as data types, functions, macros, ... and which was bootstrapped to be partly written in itself using classes, method, generic functions, ...

See for example: https://github.com/binghe/PCL

> Google is failing me here.

Really? Indeed, if you search for just "CLOS" Google doesn't find it. Duckduckgo on the other hand, gives it in the 3rd link.

I wish there was a way to compare Google searches of today with Google searches of years ago, I feel like they've been declining in quality and relevance even as I'm sure they've improved their algorithms and even with me letting them know more about me via remaining signed in when I search. Using the "date range" tool to set a maximum date on search results (in this case I just randomly picked "2006", which Google interprets as the end of that year) I get two CLOS results as the first two items and a third one a bit further down, so that method helps me sometimes, but it's not the exact comparison I want...