[mercury-users] Present state of type classes - especially for parametrized types

[Mark Brown]

On 08-Oct-2006, Jrg Roman Rudnick <joerg.rudnick at t-online.de> wrote:
> Another idea is delegating the dependency to a second type class, e.g.,
> 
> :-typeclass dependingOn(D1, D2) <= (D1 -> D1) where [].
> :-instance dependingOn(string, string) where [].
> 
> :-instance fringe(list(T1), container(T2)) <= dependingOn(T1,T2) where [ 
> ... ]
> 
> leading to:
> functional dependency not satisfied: type variable T2 occurs in
> the range of the functional dependency, but is not in the
> domain.

I'm planning to add support for this soon (that is, in the next few weeks).

Cheers,
Mark.

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