slot-missing class object slot-name operation &optional new-
value => result* slot-missing (class t) object slot-name
operation &optional new-value Arguments and Values: class---the
class of object. slot-name---a symbol (the name of a would-be
slot). operation---one of the symbols setf, slot-boundp, slot-
makunbound, or slot-value. The generic function slot-missing is
invoked when an attempt is made to access a slot in an object
whose metaclass is standard-class and the slot of the name slot-
name is not a name of a slot in that class. The default method
signals an error. The generic function slot-missing is not
intended to be called by programmers. Programmers may write
methods for it. The generic function slot-missing may be called
during evaluation of slot-value, (setf slot-value), slot-boundp,
and slot-makunbound. For each of these operations the
corresponding symbol for the operation argument is slot-value,
setf, slot-boundp, and slot-makunbound respectively. The
optional new-value argument to slot-missing