|Version 2 (modified by simonpj, 3 years ago) (diff)|
Kinds are represented as types:
type Kind = Type
Basic kinds are now represented using type constructors, e.g. the kind * is represented as
liftedTypeKind :: Kind liftedTypeKind = TyConApp liftedTypeKindTyCon 
where liftedTypeKindTyCon is a built-in PrimTyCon. The arrow type constructor is used as the arrow kind constructor, e.g. the kind * -> * is represented internally as
FunTy liftedTypeKind liftedTypeKind
It's easy to extract the kind of a type, or the sort of a kind:
typeKind :: Type -> Kind
The "sort" of a kind is always one of the sorts: TY (for kinds that classify normal types) or CO (for kinds that classify coercion evidence). The coercion kind, T1 :=: T2, is represented by PredTy (EqPred T1 T2).
(You can edit this picture here.)
- "*" is the kind of boxed values. Things like Int and Maybe Float have kind *.
- "#" is the kind of unboxed values. Things like Int# have kind #.
- "(#)" is the kind of unboxed tuples. Things like (# Int, Int #) have kind (#).
- "ArgKind" is the kind of things that can appear as arguments to functions.
- "OpenKind" is the kind of things that can appear as results of functions.