MAYBE
MAYBE
TRS:
 {
             plus(0(), y) -> y,
            plus(s(x), y) -> s(plus(x, y)),
               lt(x, 0()) -> false(),
            lt(0(), s(y)) -> true(),
           lt(s(x), s(y)) -> lt(x, y),
      fibiter(b, c, x, y) -> if(lt(c, b), b, c, x, y),
                   fib(x) -> fibiter(x, 0(), 0(), s(0())),
   if(true(), b, c, x, y) -> fibiter(b, s(c), y, plus(x, y)),
  if(false(), b, c, x, y) -> x
 }
 DUP: We consider a duplicating system.
  Trs:
   {
               plus(0(), y) -> y,
              plus(s(x), y) -> s(plus(x, y)),
                 lt(x, 0()) -> false(),
              lt(0(), s(y)) -> true(),
             lt(s(x), s(y)) -> lt(x, y),
        fibiter(b, c, x, y) -> if(lt(c, b), b, c, x, y),
                     fib(x) -> fibiter(x, 0(), 0(), s(0())),
     if(true(), b, c, x, y) -> fibiter(b, s(c), y, plus(x, y)),
    if(false(), b, c, x, y) -> x
   }
  Fail