def elo_expected(d :float ,f :float =400 )->float:
    """ Expected points scored in a match by White player
    :param d:   Difference in rating (Black minus White)
    :param f:   "F"-Factor
    :return:
    """
    if d/ f > 8:
        return 0.0
    elif d / f < -8:
        return 1.0
    else:
        return 1. / (1 + 10 ** (d / f))