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.h... 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