remove_vertical_border_strip

edit

One way to do that is using the conjugate partition.

For any partition, the conjugate partition is the one whose lines are the columns of p; analogue to the transpose for matrices.

Here is how to use it to remove vertical border strip.

sage: p = Partition([5,3,1])
sage: p
[5, 3, 1]
sage: unicode_art(p)
┌┬┬┬┬┐
├┼┼┼┴┘
├┼┴┘
└┘
sage: h = p.remove_horizontal_border_strip(1).list()
sage: h
[[5, 3], [5, 2, 1], [4, 3, 1]]
sage: unicode_art(q)
⎡         ┌┬┬┬┬┐  ┌┬┬┬┐ ⎤
⎢ ┌┬┬┬┬┐  ├┼┼┴┴┘  ├┼┼┼┘ ⎥
⎢ ├┼┼┼┴┘  ├┼┘     ├┼┴┘  ⎥
⎣ └┴┴┘  , └┘    , └┘    ⎦
sage: pc = p.conjugate()
sage: pc
[3, 2, 2, 1, 1]
sage: unicode_art(pc)
┌┬┬┐
├┼┼┘
├┼┤
├┼┘
├┤
└┘
sage: qq = [q.conjugate() for q in pc.remove_horizontal_border_strip(1)]
sage: qq
[[4, 3, 1], [5, 2, 1], [5, 3]]
sage: unicode_art(qq)
⎡ ┌┬┬┬┐  ┌┬┬┬┬┐         ⎤
⎢ ├┼┼┼┘  ├┼┼┴┴┘  ┌┬┬┬┬┐ ⎥
⎢ ├┼┴┘   ├┼┘     ├┼┼┼┴┘ ⎥
⎣ └┘   , └┘    , └┴┴┘   ⎦

One can define a corresponding function:

def remove_vertical_border_strip(p, k):
    r"""
    Return the partitions obtained from ``p`` by removing
    a vertical border strip of length ``k``.

    EXAMPLE::

        sage: p = Partition([5, 3, 1])
        sage: remove_vertical_border_strip(p, 1)
        [[4, 3, 1], [5, 2, 1], [5, 3]]
    """
    pc = p.conjugate()
    return [q.conjugate() for q in pc.remove_horizontal_border_strip(k)]

and then just use that function:

sage: p = Partition([5, 3, 1])
sage: qq = remove_vertical_border_strip(p, 1)
sage: qq
[[4, 3, 1], [5, 2, 1], [5, 3]]
sage: unicode_art(qq)
⎡ ┌┬┬┬┐  ┌┬┬┬┬┐         ⎤
⎢ ├┼┼┼┘  ├┼┼┴┴┘  ┌┬┬┬┬┐ ⎥
⎢ ├┼┴┘   ├┼┘     ├┼┼┼┴┘ ⎥
⎣ └┘   , └┘    , └┴┴┘   ⎦