(VAR y x xs f)
(RULES
  app(app(plus, 0), y) -> y
  app(app(plus, app(s, x)), y) -> app(s, app(app(plus, x), y))
  app(inc, xs) -> app(app(map, app(plus, app(s, 0))), xs)
  app(app(map, f), nil) -> nil
  app(app(map, f), app(app(cons, x), xs)) -> app(app(cons, app(f, x)), app(app(map, f), xs))
)