Random metaclasses for CL types

[Jon L White <jonl@lucid.com>]

re: Date: Wed, 24 May 89  17:35:33 CDT
    From: David N Gray <Gray@DSG.csc.ti.com>
    . . . 
    [... jonl's  inheritance diagram for FUNCTION, STANDARD-FUNCTION, etc]
    . . . 
    OK; the real issue is that if users are to be permitted to define
    subclasses of GENERIC-FUNCTION or STANDARD-FUNCTION, then they just need
    to know what to use for the :METACLASS option for their class in order
    for the inheritance to be permitted.

Right.  And I don't see any particular reason to require it to be
STANDARD-CLASS.  But even if it were to be STANDARD-CLASS, that's not 
nearly so important as the recognition that subclass relations in the 
base classes -- such as FUNCTION, STANDARD-FUNCTION, and 
STANDARD-GENERIC-FUNCTION -- don't imply any particular subclass relations 
in their metaclasses.  I think you seem to be agreeing with me on that.



re: Date: Wed, 24 May 89  18:34:43 CDT
    From: David N Gray <Gray@DSG.csc.ti.com>
    . . . 
    [suggestion that specification for the "holy" types must explicitly
     allow for STANDARD-CLASS and STRUCTURE-CLASS because of the
     openness of CLOS]
    . . . 
    I don't see why flavor classes are any different from standard classes
    in this regard.  Our implementation provides for writing CLOS methods
    that specialize on flavors and use SLOT-VALUE to access their instance
    variables.  True, flavors does have another way of writing methods that
    can be used instead, but that wouldn't necessarily be true of all
    implementation-defined metaclasses.

With respect to STANDARD-CLASS, that's precisely the point -- that there
are _no_ ways other than SLOT-VALUE, etc.  [I presume you meant "all
implementation-defined metaclasses" for built-in classes?]  But you're 
clever trick for pathnames -- letting it be implemented by a kind 
of standard class ("hidden-class") but represented by a kind of built-in
class (the "visible-class") -- shows that we could even forgo the 
special dispensation for STANDARD-CLASS and STRUCTURE-CLASS.

However, if the Gabriel plan of flushing BUILT-IN-CLASS succeeds, it
will all be moot.



-- JonL --