equality

[Ken Sailor]

Of course, as soon as I mailed my response I understand there is a deeper 
question: If you want to define a class equality that is symmetric, 
reflexive, and transitive, how do you do so?  Certainly would be nice, 
and would make reasoning about the class easier with such guarantees.

I think the answer is that you can't provide such guarantees in a class 
definition.  

The programmer when defining an instance of equality "should" provide a
definition in the spirit of equality, but the compiler can not ensure that
the definition satisfies such restrictions as x==x for all x of the 
instance type.  

Ken

------------------------------------------------------------------
Ken Sailor				sailor@cs.usask.ca
                                        sailor@sask.trlabs.ca

HyperCore Technology Inc.		University of Saskatchewan	
Senior Software Analyst			Adjunct Professor
phone 1-306-668-8218			fax 1-306-668-1944