Some Simple Programs
• eval : �A ® A
   eval (x) = let box u = x in u
• quote : �A ® ��A
   quote (x) = let box u = x in box (box u)
• app : �(A ® B) ® �A ® �B
   app (f) (x) =
         let box g = f in
              let box u = x in box (g u)