import System.Random
import qualified Data.Map as Map
import Data.Map (Map)
import Data.List
import Control.Monad.State

simulate count m n = do
 mapM (dice m) (replicate count n)

histogram :: Ord a => [a] -> [(a,Int)]
histogram = Map.assocs . foldl f Map.empty
 where
   f m k = Map.insertWith (+) k 1 m

simulation = simulate 1000000 3 6 >>= return . histogram 

main = run

{-
dice :: Int -> Int -> IO Int
dice 0 n = return 0
dice m n = do
 total <- dice (m - 1) n
 roll <- randomRIO (1, n)
 return (total + roll)

run = simulation >>= putStrLn . show
-}

die :: RandomGen g => Int -> State g Int
die n = State $ randomR (1,n)

dice :: RandomGen g => Int -> Int -> State g Int
dice m n = liftM sum $ replicateM m (die n)

run = getStdGen >>= return . evalState simulation >>= putStrLn . show