I guess so, For example, one can't do something like below in `CSymPy`.

    RCP<const Basic> im1 = rcp(new Integer(-1));
    RCP<const Basic> i2 = rcp(new Integer(2));
    RCP<const Basic> i3 = rcp(new Integer(3));
    div(i2, div(i3, mul(i2, im1)));

This generates the error I mentioned above.