Finish list affectation containing R^d by 0

Now it is possible to write
``
R^3 x=(1,2,3);
R^2 y=(1,3);

R z = 2;
(x, z, y) = (0, 3, 0);
``
This will lead to the final values: `x==(0,0,0)`, `y==(0,0)` and `z==3`
Remember that the only valid **N** value in such instruction is `0`.