import Data.List (span) main = mapM_ (putStrLn . draw) . take 20 . iterate step . initialize $ dat where draw = map (\n -> if n == 0 then ' ' else '■') dat = [1,2,3,7,8,12,13,18] initialize :: [Int] -> [Int] initialize = ini [] (-1) where ini acc _ [] = reverse acc ini acc prev (x:xs) = ini (make (x-prev)++acc) x xs make n = (1:) . take (n-1) . repeat $ 0 step ns = step' [] ns where step' acc [] =
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