:set -XTypeFamilyDependencies
:set -XDataKinds
:set -XUndecidableInstances
:set -XPolyKinds

type family F a b c = (result :: k) | result -> a b c
type instance F Int  Char Bool = Bool
type instance F Char Bool Int  = Int
type instance F Bool Int  Char = Char
type instance F Bool Int  Char = Char

type family I (a :: k) b (c :: k) = r | r -> a b
type instance I Int  Char Bool = Bool
type instance I Int  Char Int  = Bool
type instance I Bool Int  Int  = Int

type family J a (b :: k) = r | r -> a
type instance J Int b = Char

type MaybeSyn a = Maybe a
type family K a = r | r -> a
type instance K a = MaybeSyn a