A class can inherit methods, slots,
and some defclass options from its superclasses.
Other sections describe the inheritance of methods,
the inheritance of slots and slot options,
and the inheritance of class options.
(defclass C1 ()
((S1 :initform 5.4 :type number)
(S2 :allocation :class)))
(defclass C2 (C1)
((S1 :initform 5 :type integer)
(S2 :allocation :instance)
(S3 :accessor C2-S3)))
Instances of the class C1 have a local slot named S1,
whose default initial value is 5.4 and
whose value should always be a number.
The class C1 also has a shared slot named S2.
There is a local slot named S1 in instances of C2.
The default initial value of S1 is 5.
The value of S1 should always be of type (and integer number).
There are also local slots named S2 and S3 in instances of C2.
The class C2 has a method for C2-S3 for reading the value of slot S3;
there is also a method for (setf C2-S3) that writes the value of S3.
The :default-initargs class option is inherited. The set of defaulted initialization arguments for a class is the union of the sets of initialization arguments supplied in the :default-initargs class options of the class and its superclasses. When more than one default initial value form is supplied for a given initialization argument, the default initial value form that is used is the one supplied by the class that is most specific according to the class precedence list.
If a given :default-initargs class option specifies an
initialization argument of the same name more than once, an
error of type program-error is signaled.