YES(?,O(n^2))

Problem:
 rev(a()) -> a()
 rev(b()) -> b()
 rev(++(x,y)) -> ++(rev(y),rev(x))
 rev(++(x,x)) -> rev(x)

Proof:
 Matrix Interpretation Processor:
  dimension: 2
  interpretation:
                            [12]
   [++](x0, x1) = x0 + x1 + [2 ],
   
         [4]
   [b] = [2],
   
               [1 8]     [1]
   [rev](x0) = [0 1]x0 + [0],
   
         [0]
   [a] = [0]
  orientation:
              [1]    [0]      
   rev(a()) = [0] >= [0] = a()
   
              [21]    [4]      
   rev(b()) = [2 ] >= [2] = b()
   
                  [1 8]    [1 8]    [29]    [1 8]    [1 8]    [14]                    
   rev(++(x,y)) = [0 1]x + [0 1]y + [2 ] >= [0 1]x + [0 1]y + [2 ] = ++(rev(y),rev(x))
   
                  [2  16]    [29]    [1 8]    [1]         
   rev(++(x,x)) = [0  2 ]x + [2 ] >= [0 1]x + [0] = rev(x)
  problem:
   
  Qed