Skip to content

Instantly share code, notes, and snippets.

@scan scan/chan.hs
Created Jan 26, 2013

Embed
What would you like to do?
import Control.Concurrent.Chan (Chan, newChan)
import qualified Data.Map as M
import Control.Concurrent.STM (TVar, readTVar, writeTVar)
type Id = Integer
getOrCreateChannel :: (MonadIO m) => Id -> TVar (M.Map Id (Chan a)) -> m (Chan a)
getOrCreateChannel cid t = liftIO $ do
nchan <- newChan
atomically $ do
chans <- readTVar t
case M.lookup cid chans of
(Just c) -> return c
Nothing -> do
writeTVar t $ M.insert cid nchan chans
return nchan
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.