two questions about standard-class

[Sonya E. Keene <skeene@STONY-BROOK.SCRC.Symbolics.COM>]

    Date: Tue, 12 Apr 88 11:58 EDT
    From: Sonya E. Keene <skeene@STONY-BROOK.SCRC.Symbolics.COM>


    A class is considered initialized if its direct superclasses are known.
    I don't understand this; how can a class be defined without stating what
    its direct superclasses are?   

    I was also confused about class-default-direct-superclasses.    I
    understand what it is supposed to do (the method for standard-class
    ensures that standard-object is included in the CPL).   The
    documentation (page 3-14 on my draft) says if there are any supplied
    superclasses, this method returns the list of supplied superclasses and
    doesn't add standard-object to that list.    If there are no supplied
    superclasses, this method returns a list containing standard object.

    The goal of this approach seems to be not to require standard-object to
    be a direct superclass of each class (otherwise the method would always
    add standard-object to the list).   The assumption seems to be that if
    there is a supplied superclass, it already has standard-object in its
    CPL.  Does this really work?   What if you define a class and specify
    T to be the only direct superclass?  

Well, you can't do that with defclass, anyway, since Chapter 1 states
that you can't use defclass to define subclasses of a built-in class,
and t is a built-in class.    However, I don't know whether you can do
the same thing some other way, using the MOP.  (later... the 3rd
paragraph below makes me think there is a way)

I'm having trouble understanding some of the ramifications of T being a
built-in class.   It seems strange that you can't specify T as a 
superclass in the defclass form, yet you get T automatically as a
superclass (by virtue of it being a superclass of standard-object).

The MOP states that standard-object is a standard-class.   This implies
that there must be some way to define a standard-class (eg
standard-object) and include a built-in class (eg t) as a superclass.
This mechanism must be different than the normal make-instance of
standard-class, because that calls valid-superclass-p, which signals an
error if the metaclass of the superclass is not EQ with the class being
defined.   Or else the method for valid-superclass-p should make an
exception for the class T.   

    [Whatever the answer to the question, if I stated the goal of the
    approach correctly, it should probably be written down in the
    documentation.]