def broadcastable_to_str(b):
    """Return string representation of broadcastable."""
    named_broadcastable = {
        (): "scalar",
        (False,): "vector",
        (False, True): "col",
        (True, False): "row",
        (False, False): "matrix",
    }
    if b in named_broadcastable:
        bcast = named_broadcastable[b]
    else:
        bcast = ""
    return bcast