[m-dev.] Module qualification of typeclass methods

[Fergus Henderson]

On 07-Nov-2001, Peter Ross <peter.ross at miscrit.be> wrote:
> On Wed, Nov 07, 2001 at 11:05:52AM +1100, Tyson Dowd wrote:
> > I also found it difficult to explain what the requirements are of the
> > extensions that are being proposed.
> > 
> > Can you gather together a few of the example interfaces that you are
> > generating and finding difficult to use? 
> > 
> > And can you then list the problems that are happening with them?
> 
> Here is an example of one way to map the System.Object class to Mercury
> (the current way we do it).
> 
> :- module 'System'.
> 
> :- interface.
> 
> :- type 'Object'.
> :- pragma foreign_type('Object', il("[mscorlib]System.Object")).
> 
> :- implementation.
> 
>     :- module 'System__Object'
>     :- interface.
>         :- typeclass 'Object'(T) where [
>                 % Instance method
>             impure func 'GetHashCode'(T) = int
>         ].
>         :- instance 'Object'('System__Object').
>             
>             % Static method.
>         :- impure func 'Equals'('System__Object', 'System__Object') = bool
> 
>     :- implementation.
> 
>         % ...
> 
>     :- end_module.
> 
> :- end_module.
> 
> The only real problem with this approach is that to use the
> System.Object class in Mercury you need to import both the System and
> System__Object modules.  I would like a mechanism which would allow one
> to import just the System module and get all the required sub-modules at
> the same time.

Hmm... IMHO this is not a compelling example.
Why not just import both the System and System__Object modules?
That doesn't seem like such a terrible burden here.

Do you have any more compelling examples?

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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