def binary_distance(label1, label2):
    """Simple equality test.

    0.0 if the labels are identical, 1.0 if they are different.

    >>> from nltk.metrics import binary_distance
    >>> binary_distance(1,1)
    0.0

    >>> binary_distance(1,3)
    1.0
    """

    return 0.0 if label1 == label2 else 1.0