a → (b → a) is inhabited

• b → a is not inhabited

• However a → (b → a) is inhabited:

      // three ways to write the same thing
      const a b =              a           :: a -> (b -> a)
      const a   =        \b -> a           :: a -> (b -> a)
      const     = \a -> (\b -> a)          :: a -> (b -> a)