Bulat Ziganshin wrote:
btw, if you want beter efficiency, you may use unboxed references (http://haskell.org/haskellwiki/Library/ArrayRef)
Thanks for the pointer to your ArrayRef library. I've downloaded it and it will be very useful - its extremely neat that the fact that something is stored as unboxed can be hidden from the rest of the program. One thing I wondered was if the functional dependency in Data.Ref.Universal from the result type to the monad is actually necessary, since this FD prevents me adding an instance for MonadIO ie the following instance is not valid: instance MonadIO m => URef m IOURef where -- m -> r is fine -- r -> m restricts m too much Of course this isn't a big problem because I can simply define lifted versions separately ie: import Data.Ref hiding(newURef, readURef, writeURef) import GHC.Unboxed import Control.Monad.Trans -- instance MonadIO m => URef m IOURef where newURef :: (Unboxed a, MonadIO m) => a -> m (IOURef a) newURef v = liftIO $ newIOURef v readURef :: (Unboxed a, MonadIO m) => IOURef a -> m a readURef ref = liftIO $ readIOURef ref writeURef :: (Unboxed a, MonadIO m) => IOURef a -> a -> m () writeURef ref v = liftIO $ writeIOURef ref v -- test monad newtype SomeIO a = SomeIO {runSomeIO :: (IO a)} deriving (Monad, MonadIO) foo :: SomeIO Int foo = do xRef <- newURef (57::Int) readURef xRef main = do x <- runSomeIO foo print x _ <- getChar return () Anyway thanks for sharing your library. I'm going to put the URef functions above into a module so I can use the same names for URef functions (ie URef.T, new, read, write) as I'm already using for boxed refs. Best regards, Brian. -- Logic empowers us and Love gives us purpose. Yet still phantoms restless for eras long past, congealed in the present in unthought forms, strive mightily unseen to destroy us. http://www.metamilk.com