gistfile1.hs

import Data.List

intToRoman :: Int -> String
intToRoman = concat . reverse . (zipWith (\f d -> f d) fs) . split
  where
    split = unfoldr (\n -> if n > 0 then Just ((mod n 10), (div n 10)) else Nothing)
    fs = map roman [('i', 'v', 'x'), ('x', 'l', 'c'), ('c', 'd', 'm'), ('m', '$', '#')]
    roman (one, five, ten) n
      | n >= 0 && n <= 3 = replicate n one
      | n == 4           = [one, five]
      | n >= 5 && n <= 8 = five:(replicate (n - 5) one)
      | n == 9           = [one, ten]