MAYBE
Time: 0.000685
TRS:
 {              is_empty nil() -> true(),
           is_empty cons(x, l) -> false(),
                 hd cons(x, l) -> x,
                 tl cons(x, l) -> l,
       ifappend(l1, l2, nil()) -> l2,
  ifappend(l1, l2, cons(x, l)) -> cons(x, append(l, l2)),
                append(l1, l2) -> ifappend(l1, l2, l1)}
 DP:
  DP:
   {ifappend#(l1, l2, cons(x, l)) -> append#(l, l2),
                  append#(l1, l2) -> ifappend#(l1, l2, l1)}
  TRS:
  {              is_empty nil() -> true(),
            is_empty cons(x, l) -> false(),
                  hd cons(x, l) -> x,
                  tl cons(x, l) -> l,
        ifappend(l1, l2, nil()) -> l2,
   ifappend(l1, l2, cons(x, l)) -> cons(x, append(l, l2)),
                 append(l1, l2) -> ifappend(l1, l2, l1)}
  UR:
   {a(y, z) -> y,
    a(y, z) -> z}
   EDG:
    {(append#(l1, l2) -> ifappend#(l1, l2, l1), ifappend#(l1, l2, cons(x, l)) -> append#(l, l2))
     (ifappend#(l1, l2, cons(x, l)) -> append#(l, l2), append#(l1, l2) -> ifappend#(l1, l2, l1))}
    STATUS:
     arrows: 0.500000
     SCCS (1):
      Scc:
       {ifappend#(l1, l2, cons(x, l)) -> append#(l, l2),
                      append#(l1, l2) -> ifappend#(l1, l2, l1)}
      
      SCC (2):
       Strict:
        {ifappend#(l1, l2, cons(x, l)) -> append#(l, l2),
                       append#(l1, l2) -> ifappend#(l1, l2, l1)}
       Weak:
       {              is_empty nil() -> true(),
                 is_empty cons(x, l) -> false(),
                       hd cons(x, l) -> x,
                       tl cons(x, l) -> l,
             ifappend(l1, l2, nil()) -> l2,
        ifappend(l1, l2, cons(x, l)) -> cons(x, append(l, l2)),
                      append(l1, l2) -> ifappend(l1, l2, l1)}
       Open