On Tue, Dec 16, 2008 at 5:54 AM, Luke Palmer
Okay, that's a bit clearer. Control.Parallel is not what you want; that is for parallelizing pure code (and is very nice inside its little domain). But you want concurrent code: multiple threads that change state at the same time. That is in Control.Concurrent.
In particular, the "shared variable" is Data.IORef.
Simple example from which you should be able to extrapolate.
Apologies, this code doesn't compile. Here's the fixed version: import Control.Concurrent import Control.Concurrent.MVar import Data.IORef threadBody var = do x <- readIORef var writeIORef var (x+1) main = do var <- newIORef 0 -- spawn two threads forkIO (threadBody var) forkIO (threadBody var) -- look at the value of the variable x <- readIORef var print x