fpuser2663366

  • Untitled 15 Sep 2015

    import Control.Concurrent.STM import Control.Concurrent import System.Random main = do elf_gp <- newGroup 3 sequence_ [ elf elf_gp n | n <- [1..10]] rein_gp <- newGroup 9 sequence_ [ reindeer rein_gp n | n <- [1..9]] forever (santa elf_gp rein_gp) where elf gp id = forkIO (forever (do elf1 gp id randomDelay)) reindeer gp id = forkIO (forever (do reindeer1 gp id randomDelay)) santa :: Group -> Group -> IO () santa elf_group rein_group = do putStr "----------\n" choose [(awaitGroup rein_group, run "deliver toys"), (awaitGroup elf_group, run "meet in my study")] where run :: String -> (Gate,Gate) -> IO () run task (in_gate,out_gate) = do putStr ("Ho! Ho! Ho! let's " ++ task ++ "\n") operateGate in_gate operateGate out_gate helper1 :: Group -> IO () -> IO () helper1 group do_task = do (in_gate, out_gate) <- joinGroup group passGate in_gate do_task passGate out_gate elf1, reindeer1 :: Group -> Int -> IO () elf1 group id = helper1 group (meetInStudy id) reindeer1 group id = helper1 group (deliverToys id) meetInStudy id = putStr ("Elf " ++ show id ++ " meeting in the study\n") deliverToys id = putStr ("Reindeer " ++ show id ++ " delivering toys\n") --------------- data Group = MkGroup Int (TVar (Int, Gate, Gate)) newGroup :: Int -> IO Group newGroup n = atomically (do g1 <- newGate n g2 <- newGate n tv <- newTVar (n, g1, g2) return (MkGroup n tv)) joinGroup :: Group -> IO (Gate,Gate) joinGroup (MkGroup n tv) = atomically (do (n_left, g1, g2) <- readTVar tv check (n_left > 0) writeTVar tv (n_left-1, g1, g2) return (g1,g2)) awaitGroup :: Group -> STM (Gate,Gate) awaitGroup (MkGroup n tv) = do (n_left, g1, g2) <- readTVar tv check (n_left == 0) new_g1 <- newGate n new_g2 <- newGate n writeTVar tv (n,new_g1,new_g2) return (g1,g2) --------------- data Gate = MkGate Int (TVar Int) newGate :: Int -> STM Gate newGate n = do tv <- newTVar 0 return (MkGate n tv) passGate :: Gate -> IO () passGate (MkGate n tv) = atomically (do n_left <- readTVar tv check (n_left > 0) writeTVar tv (n_left-1)) operateGate :: Gate -> IO () operateGate (MkGate n tv) = do atomically (writeTVar tv n) atomically (do n_left <- readTVar tv check (n_left == 0)) ---------------- forever :: IO () -> IO () -- Repeatedly perform the action forever act = forever' act 10 where -- cheating here to make it stop eventually forever' :: IO () -> Int -> IO () forever' act 0 = return () forever' act n = do act forever' act (n - 1) randomDelay :: IO () -- Delay for a random time between 1 and 1000,000 microseconds randomDelay = do waitTime <- getStdRandom (randomR (1, 1000000)) threadDelay waitTime choose :: [(STM a, a -> IO ())] -> IO () choose choices = do to_do <- atomically (foldr1 orElse stm_actions) to_do where stm_actions :: [STM (IO ())] stm_actions = [ do val <- guard return (rhs val) | (guard, rhs) <- choices ] وتكثير الحسنات وتكفير السيئات فاجتهدوا رحمكم الله في العمل الصالح.