On 11-02-02 04:42 PM, Warren Harris wrote:
It still seems to me that haskell is lacking when it comes to operations that
can wait for multiple conditions.
STM opens the avenue to waiting for multiple conditions.
import Control.Concurrent
import Control.Concurrent.STM
import Control.Exception(finally)
data DoOrDie = Do | Die
main = do
die <- atomically newEmptyTMVar
finale <- atomically newEmptyTMVar
forkIO (timeloop die `finally` atomically (putTMVar finale ()))
putStrLn "press enter to quit"
getLine
atomically (putTMVar die Die)
atomically (takeTMVar finale)
timeloop die = run where
run = do
w <- atomically newEmptyTMVar
i <- forkIO (threadDelay 15000000 >> atomically (putTMVar w Do))
r <- atomically (takeTMVar w `orElse` takeTMVar die)
case r of
Do -> putStrLn "checkpoint" >> run
Die -> killThread i >> putStrLn "checkmate"
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