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+import Data.Kind
+
+data HList (ts :: [Type]) where
+  HNil :: HList '[]
+  (:#) :: t -> HList ts -> HList (t ': ts)
+
+infixr 5 :#
+
+type family All (c :: Type -> Constraint) (ts :: [Type]) :: Constraint where
+  All c '[] = ()
+  All c (t ': ts) = (c t, All c ts)
+
+instance All Eq ts => Eq (HList ts) where
+  HNil == HNil = True
+  (a :# as) == (b :# bs) = a == b && as == bs
+
+-- Exercise 5.3-iii
+-- Rewrite the `Ord` and `Show` instances in terms of `All`:
+instance (All Eq ts, All Ord ts) => Ord (HList ts) where
+  compare HNil HNil = EQ
+  compare (a :# as) (b :# bs) = compare a b <> compare as bs
+
+instance All Show ts => Show (HList ts) where
+  show HNil = "HNil"
+  show (a :# as) = show a <> " :# " <> show as