On Sun, Aug 23, 2009 at 1:33 AM, Michael Speer
data HashTable a b = HashTable (a -> Int) (STM (Array Int (TVar (Maybe b))))
So wait... a HashTable is a hash function together with an *action returning an array of TVars?* I don't think that's right. It looks like that action is recreating an empty table each time it is accessed. You probably want: data HashTable a b = HashTable (a -> Int) (TVar (Array Int (TVar (Maybe b)))) instead. The rest of the implementation will follow the type.
mkHashTable :: ( a -> Int ) -> Int -> HashTable a b mkHashTable hashfn numBuckets | numBuckets > 0 = do HashTable hashfn $ do vs <- mapM (\v -> newTVar Nothing >>= \tv -> return (v,tv) ) [1..numBuckets] return $ array (1,numBuckets) vs
readHashTable :: HashTable a b -> a -> STM (Maybe b) readHashTable hashtable key = let (HashTable hashfn table) = hashtable in table >>= \tb -> readTVar (tb ! hashfn key)
writeHashTable :: HashTable a b -> a -> (Maybe b) -> STM () writeHashTable hashtable key value = let (HashTable hashfn table) = hashtable in table >>= \tb -> writeTVar (tb ! hashfn key) value >> return ()
main = let ht = mkHashTable id 10 :: HashTable Int String in do v <- atomically $ do mapM_ (\n -> writeHashTable ht n (Just $ "hello " ++ show n)) [1..10] mapM (\n -> readHashTable ht n) [1..10] print v _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe