Re: Common Lisp Types

[Danny Bobrow <Bobrow.pa@Xerox.COM>]

    From the application programmer's viewpoint, classes for some
    of the types listed as not having any would make application
    development using CLOS more straightforward. Consider the STREAM
    type. If a STREAM class exists, and is subclass-able, then
    developing a window system application which can run on a variety
    of displays becomes easier, since WINDOW can be a subclass of
    STREAM. In this sense, I think Gabrial's proposal is a sound one,
    since it increases the integration between the CL type system and
    CLOS. 
 		Jim Kempf	kempf@hplabs.hp.com
I believe having abstract classes is great.  The problem becomes when
the user expects a method to be applicable, but it isn't because the
type (class) system doesn't preserve the appropriate subclass
relationships.  For example, will the type (class) system support

(subclassp (class-of #'(lambda(x) x)) (class-named 'function))

If so, then function is a good class;  if not, then I think there is
some confusion.  If all implementations of stream are such that 
(subclassp (class-of *stream-object*) (class-named 'stream))
then stream is a good class.

Thus, I believe in most of what RPG suggested.  But we should be careful
not to break the users model of the class system.  

  danny