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ANSI Common Lisp  7 Objects 7.7 Dictionary of Objects
| 7.7.12 slot-missing |
Standard Generic Function |
- Syntax:
-
slot-missing
class object slot-name operation &optional new-value
 {result}*
- Method Signatures:
-
slot-missing
(class t)
object slot-name
operation &optional new-value
- Arguments and Values:
-
class - the class of object.
object - an 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.
new-value - an object.
result - an object.
- Description:
-
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 is used
when the operation is attempting to set the value of the slot.
If slot-missing returns, its values will be treated as follows:
- Exceptional Situations:
-
The default method on slot-missing
signals an error of type error.
- See Also:
-
defclass,
slot-exists-p,
slot-value
- Notes:
-
The set of arguments (including the class of the instance) facilitates
defining methods on the metaclass for slot-missing.
- Allegro CL Implementation Details:
-
None.
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