import System
import Maybe
import Data.HashTable

update ht1 ht2 key = do
    (Just x) <- Data.HashTable.lookup ht1 key
    maybey   <- Data.HashTable.lookup ht2 key
    case maybey of
       Just y  -> do delete ht2 key; insert ht2 key (x+y)
       Nothing -> do insert ht2 key x

applyEach [] = return ()
applyEach (x:xs) = x >> applyEach xs

main = do
    [n] <- getArgs

    let elements = [0..9999]
	keys = map (\x -> "foo_"++(show x)) elements

    ht1 <- fromList hashString $ zip keys elements
    ht2 <- new (==) hashString :: IO (HashTable String Int)

    -- foldr (<<) $ concat $ replicate (read n) [ update ht1 ht2 key | key <- keys ]
    -- applyEach [ applyEach $ replicate (read n) $ update ht1 ht2 key | key <- keys ]
    -- sequence_ $ concat $ replicate (read n) [ update ht1 ht2 key | key <- keys ]

    sequence_ [ sequence_ $ replicate (read n) $ update ht1 ht2 key | key <- keys ]

    vals <- sequence [Data.HashTable.lookup ht1 "foo_1"     
                     ,Data.HashTable.lookup ht1 "foo_9999"  
                     ,Data.HashTable.lookup ht2 "foo_1"     
                     ,Data.HashTable.lookup ht2 "foo_9999"  
	             ]
    putStrLn $ unwords $ map (show . fromJust) vals