module Main (main) where

import Control.Concurrent
import Control.Concurrent.STM


fib :: Integer -> Integer
fib 0 = 1
fib 1 = 1
fib x = (fib $ x - 1) + (fib $ x - 2)

intensive tv n = atomically $ putTMVar tv $! (fib n)


main = do t1 <- newEmptyTMVarIO
          t2 <- newEmptyTMVarIO
          forkIO $ intensive t1 37
          putStrLn "Launched first"
          forkIO $ intensive t2 38
          putStrLn "Launched second"
          r1 <- atomically $ readTMVar t1
          r2 <- atomically $ readTMVar t2
          print r1
          print r2