MAYBE
Trs:
 {                  app(app(takeWhile(), p), nil()) -> nil(),
  app(app(takeWhile(), p), app(app(cons(), x), xs)) -> app(app(app(if(), app(p, x)), app(app(cons(), x), app(app(takeWhile(), p), xs))), nil()),
                    app(app(dropWhile(), p), nil()) -> nil(),
  app(app(dropWhile(), p), app(app(cons(), x), xs)) -> app(app(app(if(), app(p, x)), app(app(dropWhile(), p), xs)), app(app(cons(), x), xs)),
                  app(app(app(if(), true()), x), y) -> y,
                  app(app(app(if(), true()), x), y) -> x}
 Comment:
  We consider a duplicating trs.
  FAIL:
   Open