slot-makunbound (ANSI and GNU Common Lisp Document)

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#### 7.7.11 slot-makunbound [Function]

`slot-makunbound` instance slot-name ⇒ instance

#### Arguments and Values::

instance – instance.

Slot-name—a symbol.

#### Description::

The function slot-makunbound restores a slot of the name slot-name in an instance to the unbound state.

#### Exceptional Situations::

If no slot of the name slot-name exists in the instance, slot-missing is called as follows:

    (slot-missing (class-of instance)
                  instance
                  slot-name
                  'slot-makunbound)

(Any values returned by slot-missing in this case are ignored by slot-makunbound.)

The specific behavior depends on instance’s metaclass. An error is never signaled if instance has metaclass standard-class. An error is always signaled if instance has metaclass built-in-class. The consequences are undefined if instance has any other metaclass–an error might or might not be signaled in this situation. Note in particular that the behavior for conditions and structures is not specified.

#### See Also::

slot-boundp , slot-missing

#### Notes::

Although no implementation is required to do so, implementors are strongly encouraged to implement the function slot-makunbound using the function `slot-makunbound-using-class` described in the Metaobject Protocol.