I was wondering if it was possible to implement synchronous channels
within STM. In particular, I'd like to have CSP-like send and recv primitives
on a channel that each block until the other side arrives to complete
the transaction.
Assuming that retry blocks until something changes, you could associate
a channel with a thread that encapsulates the transaction. Somewhat like this?
import Control.Concurrent.STM
import Control.Concurrent
sender write confirm = do
atomically $ putTMVar write "hi"
atomically $ takeTMVar confirm
putStrLn "sender done"
receiver read = do
r <- atomically $ takeTMVar read
putStrLn $ "receiver done: "++r
channel read write confirm = atomically $ do
w <- takeTMVar write
putTMVar read w
putTMVar confirm ()
main = do
(read,write,confirm) <- atomically $ do
read <- newEmptyTMVar
write <- newEmptyTMVar
confirm <- newEmptyTMVar
return (read,write,confirm)
forkIO (channel read write confirm)
forkIO (threadDelay 3000000 >> receiver read)
threadDelay 5000000 >> sender write confirm
You might also be interested in
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/chp
Claus
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