import Data.List (unfoldr, transpose)
import Control.Arrow (second)

dat =
  "Given$a$text$file$of$many$lines,$where$fields$within$a$line$\n" ++
  "are$delineated$by$a$single$'dollar'$character,$write$a$program\n" ++
  "that$aligns$each$column$of$fields$by$ensuring$that$words$in$each$\n" ++
  "column$are$separated$by$at$least$one$space.\n" ++
  "Further,$allow$for$each$word$in$a$column$to$be$either$left$\n" ++
  "justified,$right$justified,$or$center$justified$within$its$column.\n"

brkdwn =
  takeWhile (not . null) . unfoldr (Just . second (drop 1) . span ('$' /=))

format j ls = map (unwords . zipWith align colw) rows
  where
    rows = map brkdwn $ lines ls
    colw = map (maximum . map length) . transpose $ rows
    align cw w =
      case j of
        'c' -> replicate l ' ' ++ w ++ replicate r ' '
        'r' -> replicate dl ' ' ++ w
        'l' -> w ++ replicate dl ' '
      where
        dl = cw - length w
        (l, r) = (dl `div` 2, dl - l)