Hello Einar, Tuesday, September 13, 2005, 7:03:00 PM, you wrote: EK> data Packet = Packet Word32 Word32 Word32 [FastString] well. you can see my own BinaryStream package at http://freearc.narod.ru class BinaryData a where read :: ... write :: ... instance BinaryData Word32 where read = ... write = ... instance BinaryData FastString where read = ... write = ... instance (BinaryData a, BinaryData b, BinaryData c, BinaryData d) => BinaryData (a,b,c,d) where read = ... write = ... instance (BinaryData a) => BinaryData [a] where read = ... write = ... EK> 1) Simple monadic interface EK> getPacket = do mid <- getWord32BE EK> sid <- getWord32BE EK> rid <- getWord32BE EK> nmsg<- getWord32BE EK> vars<- replicateM (fromIntegral nmsg) (getWord32BE >>= getBytes) EK> return $ Packet mid sid rid nmsg vars turns into: (a,b,c,d) <- read return $ Packet a b c d EK> Maybe even the tuple could be eliminated by using a little of TH. it may be eliminated even without TH! :+: and :*: should work, although i don't tried this -- Best regards, Bulat mailto:bulatz@HotPOP.com