YES
O(n^4)
TRS:
 {
       rev(a()) -> a(),
       rev(b()) -> b(),
  rev(++(x, y)) -> ++(rev(y), rev(x)),
  rev(++(x, x)) -> rev(x)
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
         rev(a()) -> a(),
         rev(b()) -> b(),
    rev(++(x, y)) -> ++(rev(y), rev(x)),
    rev(++(x, x)) -> rev(x)
   }
  Matrix Interpretation:
   Interpretation class: triangular
        [X7]  [X3]    [1 0 0 0][X7]   [1 0 0 0][X3]   [0]
        [X6]  [X2]    [0 0 0 0][X6]   [0 0 0 0][X2]   [0]
   [++]([X5], [X1]) = [0 0 0 0][X5] + [0 0 0 0][X1] + [0]
        [X4]  [X0]    [0 0 0 1][X4]   [0 0 0 1][X0]   [1]
   
         [0]
         [1]
   [b] = [1]
         [1]
   
         [X3]    [1 0 0 1][X3]   [0]
         [X2]    [0 0 0 1][X2]   [0]
   [rev]([X1]) = [0 0 0 1][X1] + [0]
         [X0]    [0 0 0 1][X0]   [0]
   
         [0]
         [0]
   [a] = [0]
         [1]
   
   
   Qed