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

[Fergus Henderson]

Thomas Charles CONWAY, you wrote:
> 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.

Well, the declarative semantics is the same for all modes.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>   |  "I have always known that the pursuit
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