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+import Data.Kind
+
+data HList (ts :: [Type]) where
+  HNil :: HList '[]
+  (:#) :: t -> HList ts -> HList (t ': ts)
+
+infixr 5 :#
+
+instance Eq (HList '[]) where
+  HNil == HNil = True
+
+instance (Eq t, Eq (HList ts)) => Eq (HList (t ': ts)) where
+  (a :# as) == (b :# bs) = a == b && as == bs
+
+-- Exercise 5.3-i
+-- Implement `Ord` for `HList`:
+instance Ord (HList '[]) where
+  compare HNil HNil = EQ
+
+-- I always forget `Ord` is a monoid. This version is less elegant, but works
+-- just as well as Sandy's:
+instance (Ord t, Ord (HList ts)) => Ord (HList (t ': ts)) where
+  compare (a :# as) (b :# bs) =
+    case compare a b of
+      EQ -> compare as bs
+      other -> other
+
+-- Exercise 5.3-ii
+-- Implement `Show` for `HList`:
+instance Show (HList '[]) where
+  show HNil = "HNil"
+
+instance (Show t, Show (HList ts)) => Show (HList (t ': ts)) where
+  show (a :# as) = show a <> " :# " <> show as