The generic function reinitialize-instance may be used to change
the values of slots according to initialization arguments.
The process of reinitialization changes the values of some slots and performs any user-defined actions. It does not modify the structure of an instance to add or delete slots, and it does not use any :initform forms to initialize slots.
The generic function reinitialize-instance may be called
directly. It takes one required argument, the instance. It also
takes any number of initialization arguments to be used by methods for
reinitialize-instance or for shared-initialize. The
arguments after the required instance must form an
initialization argument list.
There is a system-supplied primary method for
reinitialize-instance whose parameter specializer is
the class standard-object. First this method checks the validity of
initialization arguments and signals an error if an initialization
argument is supplied that is not declared as valid.
(For more information, see Section 7.1.2 (Declaring the Validity of Initialization Arguments).)
Then it calls the generic function
shared-initialize with the following arguments: the instance,
nil, and the initialization arguments it received.