YES(?,O(n^2))
TRS:
 {  f +(x, 0()) -> f x,
  +(x, +(y, z)) -> +(+(x, y), z)}
 DUP: We consider a non-duplicating system.
  Trs:
   {  f +(x, 0()) -> f x,
    +(x, +(y, z)) -> +(+(x, y), z)}
  Matrix Interpretation:
   Interpretation class: triangular
         [1]
   [0] = [2]
   
       [X3]  [X1]    [1 0][X3]   [1 1][X1]   [2]
   [+]([X2], [X0]) = [0 1][X2] + [0 1][X0] + [2]
   
       [X1]    [1 0][X1]   [0]
   [f]([X0]) = [0 0][X0] + [0]
   
   
   Qed