Kindness of strangers (or strangeness of Kinds)

AntC anthony_clayden at
Tue Jun 12 08:26:46 CEST 2012

Edward Kmett <ekmett <at>> writes:

> On Mon, Jun 11, 2012 at 9:58 PM, AntC <anthony_clayden <at>> 
>> [snip ...]
>> Could we have :k (->) :: OpenKind -> * -> *  -- why not?
> I don't quite understand why you would want arbitrary kinded arguments, but 
only in negative position. 

Thanks Edward, oops I've used the wrong terminology, sorry for the confusion. 
I didn't mean OpenKind but AnyKind. I put that only in a negative position 
more to sharpen the question, but also because I assumed the result from (->) 
would have to be grounded in Kind *; and then at least one of its arguments 
would also have to be grounded in Kind *.

I think perhaps(?) more PolyKindness is on the horizon:  (section on GADKs, and sub-
pages on KindPolymorphism and ExplicitTypeApplication). I guess GHC is getting 
there by small steps, and doesn't yet have powerful enough Kind refinement nor 
Kind equality constraints, nor interleaving of Type and Kind inference.

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