[mercury-users] constructor class syntax

[Michael Day]

> :- class mappable(F) where
> [
> 	pred map(pred(A, B), F(A), F(B)),
> 	mode map(in, in, out) is det
> ].
> 
> :- instance mappable(list) where
> [
> 	pred(map/3) is list__map
> ].

Yes that is what I mean, for some reason I thought there would be
confusion about the arity of the "list" mentioned in the instance
declaration. But of course the type class mappable requires a type
constructor of arity 1, which does not need to be restated explicitly.

Michael


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