On Tue, May 12, 2009 at 13:27, Thomas Friedrich <info@suud.de> wrote:

Hi everyone,

I have a problem with the following example in the Real World Haskell book, which aims to develop a module for controlling different threads. See,

http://book.realworldhaskell.org/read/concurrent-and-multicore-programming.html

in the chapter "The main thread and waiting for other threads".

-- file: ch24/NiceFork.hs
import Control.Concurrent
import Control.Exception (Exception, try)
import qualified Data.Map as M

data ThreadStatus = Running
| Finished -- terminated normally
| Threw Exception -- killed by uncaught exception
deriving (Eq, Show)

-- | Create a new thread manager.
newManager :: IO ThreadManager

-- | Create a new managed thread.
forkManaged :: ThreadManager -> IO () -> IO ThreadId

-- | Immediately return the status of a managed thread.
getStatus :: ThreadManager -> ThreadId -> IO (Maybe ThreadStatus)

-- | Block until a specific managed thread terminates.
waitFor :: ThreadManager -> ThreadId -> IO (Maybe ThreadStatus)

-- | Block until all managed threads terminate.
waitAll :: ThreadManager -> IO ()

When I run this through ghci I get the following failure:

[1 of 1] Compiling NiceFork ( NiceFork.hs, interpreted )

NiceFork.hs:17:26:
Class `Exception' used as a type
In the type `Exception'
In the data type declaration for `ThreadStatus'
Failed, modules loaded: none.

Any idea on how to solve this? Exception is a class not a type, so what to put there instead?

Cheers,
Thomas

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