{-# OPTIONS_GHC -fglasgow-exts -Wall #-}

import Data.Char (toUpper)
import Data.List (concat, intersperse)

rtoa :: Char -> Int
rtoa 'M' = 1000
rtoa 'D' =  500
rtoa 'C' =  100
rtoa 'L' =   50
rtoa 'X' =   10
rtoa 'V' =    5
rtoa 'I' =    1
rtoa r   = error $ "Invalid rtoa char:" ++ show r

urtoa :: Char -> Int
urtoa = rtoa . toUpper

roman_to_dec :: String -> Int
roman_to_dec = foldl1 (\t n -> t+n-t`mod`n*2) . map urtoa

myshow :: (String -> Int) -> String -> String
myshow fn val = val ++ ": " ++ (show (fn val))

testdata :: [String]
testdata = [ "XLII", "LXIX", "mi" ]

main :: IO ()
main = do
  putStrLn $ (concat $ intersperse "\n" (map (\c -> (myshow roman_to_dec c)) testdata))