Beat by a few minutes again, as piokuc says, it's in the standard. But even so, it may still be implemented as "just a library" in some CL implementations. That's the beauty of the language, it's so versatile you can extend it within itself, and it really feels like a language extension and not like you're accessing yet another API. If someone wanted a different object system, they could produce it within CL giving totally different OO semantics.
