Re: Are isomorphic structures EQUAL?

[Bobrow.pa@Xerox.COM (Danny Bobrow)]

 "I would mildly object to having [EQUAL] recursively compare components
  because that seems to be a violation of the data abstraction
capability
  that structures are supposed to provide."

One of the proposed uses for a multi-methods in CommonLoop was to allow
methods that declared themselves as -inside- both structures, and have
the system ensure that it was called in just such a case.  It would seem
that EQUAL and others are good candidates for such methods.

  "I would like to change the language so that the the type of
structures
  (whose DEFSTRUCT doesn't use :TYPE) is disjoint from other types." 

I agree on the utility of providing easy mechanisms to suport
disjointness.  Are there implementations out there that do not support
opaque types?
----- dgb: