MAYBE
MAYBE
TRS:
 {
   app(app(app(if(), true()), x), y) -> x,
  app(app(app(if(), false()), x), y) -> y,
     app(app(app(until(), p), f), x) ->
  app(app(app(if(), app(p, x)), x), app(app(app(until(), p), f), app(f, x)))
 }
 DUP: We consider a duplicating system.
  Trs:
   {
     app(app(app(if(), true()), x), y) -> x,
    app(app(app(if(), false()), x), y) -> y,
       app(app(app(until(), p), f), x) ->
    app(app(app(if(), app(p, x)), x), app(app(app(until(), p), f), app(f, x))
    )
   }
  Fail