I suppose having a good description of what I'd like to do might help: I'd like to be able to make an N-Tuple an instance of a type class. class Foo a where .... instance Foo (,) where .... instance Foo (,,) where .... The different kindedness of (,) and (,,) prevent this from working. /jve On Mon, Mar 30, 2009 at 2:00 PM, Martijn van Steenbergen < martijn@van.steenbergen.nl> wrote:
John Van Enk wrote:
Haskell not having 'polymorphic kinds'. Is there a good description of why Haskell doesn't have polymorphic kinds?
IANA expert but polymorphic kinds belong to a set of reasonably new influences (e.g. from dependently typed programming languages and generic programming) and they haven't been 1) polished enough to be a widely accepted standard or 2) simply haven't been implemented yet (low priority, etc).
Besides that, I sometimes see polymorphic kinds in GHC error messages, so I suspect that at least parts of GHC already support them.
Martijn.
-- /jve