af902bf9 ​

input = fill 10v (fill 10h black) |> fold (λr. rect ((r.1, r.2, r.1, r.2), yellow)) #0
output = fill 10v (fill 10h black) |> fold rect #1
(UList (VInt, HInt), UList ((VInt, HInt, VInt, HInt), Color))
({(6v, 6h), (6v, 4h), (4v, 6h), (4v, 4h)}, {((6v, 6h, 6v, 6h), yellow), ((6v, 4h, 6v, 4h), yellow), ((5v, 5h, 5v, 5h), red), ((4v, 6h, 4v, 6h), yellow), ((4v, 4h, 4v, 4h), yellow)})
({(7v, 7h), (7v, 2h), (2v, 7h), (2v, 2h)}, {((7v, 7h, 7v, 7h), yellow), ((7v, 2h, 7v, 2h), yellow), ((3v, 3h, 6v, 6h), red), ((2v, 7h, 2v, 7h), yellow), ((2v, 2h, 2v, 2h), yellow)})
({(10v, 10h), (10v, 5h), (7v, 10h), (7v, 5h), (4v, 4h), (4v, 2h), (2v, 4h), (2v, 2h)}, {((10v, 10h, 10v, 10h), yellow), ((10v, 6h, 10v, 9h), black), ((10v, 5h, 10v, 5h), yellow), ((8v, 10h, 9v, 10h), black), ((7v, 10h, 7v, 10h), yellow), ((8v, 6h, 9v, 9h), red), ((7v, 5h, 7v, 5h), yellow), ((4v, 4h, 4v, 4h), yellow), ((4v, 2h, 4v, 2h), yellow), ((3v, 3h, 3v, 3h), red), ((2v, 4h, 2v, 4h), yellow), ((2v, 2h, 2v, 2h), yellow)})
({(9v, 1h), (6v, 1h), (5v, 10h), (1v, 10h), (1v, 6h), (9v, 4h), (6v, 4h), (5v, 6h)}, ?)