Re: [Haskell-cafe] Possible bug in Control.Concurrent

On 09/02/11 15:34, Krzysztof Skrzętnicki wrote:

Hello Cafe,

Here is a simple program that yields strange results:

module Main where

import Control.Concurrent import Control.Concurrent.Chan import Control.Monad

main = do c <- newChan writeChan c 1 forkIO $ forever $ do i <- readChan c print ("forkio",i) isEmptyChan c >>= print

Now, this is strange thing: we put single element into the channel. We take it out.

What your program does is put a single element into the channel, and then *repeatedly* try to take one out (notice the forever you have in there!). Judging by the results, the program deadlocks, which seems like a reasonable outcome to me. Thanks, Neil.