Matrix.set

{
      // Creating matrix
      auto m = Matrix3i
      (
           3, -1, 6,
           2,  1, 5,
          -3,  1, 0
      );

      // Testing some value to be the same as added
      assert (m[2][0] == -3);

      // Setting all values to zero.
      m.set
      (
          0, 0, 0,
          0, 0, 0,
          0, 0, 0
      );

      // Testing some values to be zero. 
      assert (m[0][0] == 0);