
A Brief Guide to CLOS - Tomte
http://www.aiai.ed.ac.uk/~jeff/clos-guide.html
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flavio81
Good point in this guide: A little known fact is that, in CL, it's also
"objects all the way down":

 _It turns out that all Common Lisp data objects are instances of classes.
Consequently, you can define methods for all kinds of existing object types
(such as numbers, hash-tables, and vectors); you don 't have to use defclass
at all before defining methods. Moreover, the objects created using defclass
and make-instance can be used with ordinary Lisp functions, not only with
methods.

To find the class of an object, use the function class-of. For example:_

    
    
        Expression	Value
        (class-of 'a)	#<Built-In-Class SYMBOL>
        (class-of "a")	#<Built-In-Class STRING>
        (class-of 12)	#<Built-In-Class INTEGER>
        (class-of '(a b))	#<Built-In-Class CONS>
        (class-of '#(a b c))	#<Built-In-Class VECTOR>

