3aa6fb7a ​

input = fill 7v (fill 7h black) |> fold (λr. rect (r, teal)) #0
output = fill 7v (fill 7h black) |> fold (λr. rect ((r.1 + 1 - 1 | r.1, r.2 + 1 - 1 | r.2, r.1 + 1, r.2 + 1), teal)) #1 |> fold (λr. rect ((r, #2, r, #3), blue)) #4 |> rect ((2v, #5.1, 2v, #5.2), blue)
(UList (VInt, HInt, VInt, HInt), UList (VInt, HInt), HInt, HInt, UList VInt, (HInt, HInt))
({(4v, 6h, 5v, 6h), (4v, 5h, 4v, 6h), (3v, 2h, 3v, 3h), (2v, 2h, 3v, 2h)}, {(4v, 5h), (2v, 2h)}, 5h, 5h, {5v}, (3h, 3h))
({(7v, 4h, 7v, 5h), (6v, 5h, 7v, 5h), (1v, 6h, 2v, 6h), (1v, 5h, 1v, 6h), (4v, 3h, 4v, 4h), (3v, 3h, 4v, 3h)}, {(6v, 4h), (1v, 5h), (3v, 3h)}, 4h, 4h, {6v, 3v}, (5h, 5h))
({(7v, 1h, 7v, 2h), (6v, 2h, 7v, 2h), (2v, 1h, 2v, 2h), (2v, 1h, 3v, 1h), (1v, 7h, 2v, 7h), (1v, 6h, 1v, 7h), (5v, 4h, 5v, 5h), (4v, 4h, 5v, 4h)}, ?, ?, ?, ?, (?, ?))