def binary_search_contains(ordered, target):
    """Use binary array search to determine if target is in collection """

    low  = 0
    high = len(ordered) - 1
    while low <= high:
        mid = (low + high) / 2
        if target == ordered[mid]:
            return True # found it!
        elif target < ordered[mid]:
            high = mid - 1
        else:
            low = mid + 1
    # not found
    return False