> module Register (startup, rLookup, rNew, rDelete,rDump, stop, Register)
>  where

> import DHSCore (PidInt)
 
#ifdef CONCDEBUG

> import ConcurrentDebug as Concurrent

#else

> import ConcurrentDebugLess as Concurrent

#endif

> import IO

XXX Won´t check for duplicate entries

> type Answer = MVar (Maybe PidInt)
> data Msgs = Lookup String Answer | New String PidInt | Delete String | Dump | Stop

> data Register = RegRR {
>   chan :: Chan Msgs
>  }

> class RegisterC a where
>   rLookup :: a -> String -> IO (Maybe PidInt)
>   rNew    :: a -> String -> PidInt -> IO Bool
>   rDelete :: a -> String -> IO ()
>   rDump   :: a -> IO ()
>   stop    :: a -> IO ()

> instance RegisterC Register where
>   rLookup reg str = do
>     m <- newEmptyMVar
>     writeChan (chan reg) (Lookup str m)
>     res <- takeMVar m
>     return res

XXX

>   rNew reg str ch = do
>     writeChan (chan reg) (New str ch)
>     return True

>   rDelete reg str =
>     writeChan (chan reg) (Delete str)

>   rDump reg =
>     writeChan (chan reg) Dump

>   stop reg =
>     writeChan (chan reg) Stop

> startup = do
>   ch <- newChan
>   labelChan ch "Register.In"
>   forkIOLabel "Register" (registered ch [])
>   let reg = RegRR {
>     chan = ch
>    }
>   return reg

> registered ::	Chan Msgs -> [(String,PidInt)] -> IO ()
> registered inch list = do
>   v <- readChan inch
>   case v of
>     Lookup str out -> do
>       putMVar out (lookup str list)
> 	registered inch list
>     New str pid -> do
>       registered inch (insert list str pid)
>     Delete str -> do
> 	registered inch (delete list str)
>     Dump -> do
>       print (map fst list)
> 	registered inch list
>     Stop -> return ()
>  where
>    insert l key value = ((key,value) : l)
>    delete l key = filter (\(name,_) -> name /= key) l -- XXX suboptimal