ANSI Common Lisp   4 Types and Classes   4.3 Classes   4.3.1 Introduction to Classes

4.3.1.1 Standard Metaclasses

• The class standard-class is the default class of classes defined by defclass.

• The class built-in-class is the class whose instances are classes that have special implementations with restricted capabilities. Any class that corresponds to a standard type might be an instance of built-in-class. The predefined type specifiers that are required to have corresponding classes are listed in Figure 4.3.7 Integrating Types and Classes. It is implementation-dependent whether each of these classes is implemented as a built-in class.

• All classes defined by means of defstruct are instances of the class structure-class.