def get_polarimeter_index(pol_name):
    """Return the progressive number of the polarimeter within the board (0…7)

    Args:
        pol_name (str): Name of the polarimeter, like ``R0`` or ``W3``.

    Returns:
        An integer from 0 to 7.
    """

    if pol_name[0] == "W":
        return 7
    else:
        return int(pol_name[1])