[m-dev.] Re: proposal: user-defined equality predicates

[Thomas Charles CONWAY]

Fergus Henderson, you write:
> Andrew Bromage, you wrote:
> > > My rationale for wanting this is that non-canonical types don't work in
> > > Mercury (or any other logic programming language I know of).  Fergus'
> > > set-as-unordered-list example illustrates it quite well.
> > 
> > I understand why implementing sets as unordered lists and defining
> > equality on them in a nice way is a good idea.  However I think that
> > it is incorrect to overload =/2 in this way.  What I think would be
> > better is to handle this in type classes...
> 
> (Terminology nit: we're not really overloading =/2.  We're just defining
> its semantics when applied to different types.)
> 

Terminology nit nit: we're not just defining its semantics applied to
different types. We're defining its semantics when applied to some modes
of unification for different types.

-- 
ZZ:wq!
^X^C
Thomas Conway               				      conway at cs.mu.oz.au
AD DEUM ET VINUM	  			      Every sword has two edges.