def _eval_diff(operator, diff):
    """Return the boolean result for operator given diff.

    :param diff: An int with negative values meaning the right most parameter
        to the _eval function was greater than the left most parameter.
    :return: True if the operator was satisfied.
    """
    if operator == '==':
        return diff == 0
    if operator == '!=':
        return diff != 0
    if operator == '<':
        return diff < 0
    if operator == '<=':
        return diff <= 0
    if operator == '>':
        return diff > 0
    if operator == '>=':
        return diff >= 0
