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+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE TypeFamilies #-}
+
+-- Exercise 10.2-i
+-- Defunctionalize `listToMaybe` at the type-level.
+
+import Data.Kind (Type)
+
+type Exp a = a -> Type
+
+type family Eval (e :: Exp a) :: a
+
+data ListToMaybe :: [a] -> Exp (Maybe a)
+
+type instance Eval (ListToMaybe '[]) = 'Nothing
+
+type instance Eval (ListToMaybe (x ': _)) = 'Just x