[m-dev.] Constructor classes / Functional dependencies

[Michael Day]

> It's high on my list of things-to-do when I start working on Mercury
> full time in October (unless someone is already on the case.)

Ah, good news!

> I *think* functional dependencies at least should be fairly easy to
> add.

>From my somewhat vague thoughts on the issue, it seems that the trickiest
part would be lifting the restrictions on instance declarations and
constraints to make type classes with multiple parameters more practical.

:- typeclass foo(A, B) given A >> B.

:- instance foo(list(T), T). % an error in the second parameter

:- pred bar(C) <= foo(C, int).	% an error in the constraint

...

Michael

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