CLASS-CHANGED and UPDATE-OBSOLETE-INSTANCE

[David A. Moon <Moon@STONY-BROOK.SCRC.Symbolics.COM>]

    Date: Thu, 01 Oct 87 10:02:35 MST
    From: kempf%hplabsz@hplabs.HP.COM

    Aren't these generic functions essentially doing the same thing?

No, because CLASS-CHANGED inherently involves two classes, but
UPDATE-OBSOLETE-INSTANCE inherently involves one class.  They used
to do, and be, the same thing, before we simplified class redefinition
a couple of weeks ago.

Recall that CLASS-CHANGED methods can take advantage of abstractions,
rather than knowing about slots.  Abstraction seems particularly
important when more than one class is involved.