MAYBE
MAYBE
TRS:
 {
          app(app(app(consif(), true()), x), ys) -> app(app(cons(), x), ys),
         app(app(app(consif(), false()), x), ys) -> ys,
  app(app(filter(), f), app(app(cons(), x), xs)) ->
  app(app(app(consif(), app(f, x)), x), app(app(filter(), f), xs)),
                    app(app(filter(), f), nil()) -> nil()
 }
 DUP: We consider a duplicating system.
  Trs:
   {
            app(app(app(consif(), true()), x), ys) -> app(app(cons(), x), ys),
           app(app(app(consif(), false()), x), ys) -> ys,
    app(app(filter(), f), app(app(cons(), x), xs)) ->
    app(app(app(consif(), app(f, x)), x), app(app(filter(), f), xs)),
                      app(app(filter(), f), nil()) -> nil()
   }
  Fail