Hello another Hugs error. seem that this `instance BlockStream IO h` forces Higs to think that all BlockStream instances will belong to an IO monad. as in the previous case, all works fine with GHC {-# OPTIONS_GHC -fglasgow-exts -fallow-undecidable-instances #-} class (Monad m) => Stream m h | h -> m where class (Stream m h) => CharStream m h where class (Stream m h) => BlockStream m h where vPutBuf :: h -> m () instance (CharStream IO h) => BlockStream IO h where vPutBuf h = return () test :: (BlockStream m h) => h -> m () test file = vPutBuf file ERROR file:.\a.hs:11 - Inferred type is not general enough *** Expression : test *** Expected type : BlockStream a b => b -> a () *** Inferred type : BlockStream IO a => a -> IO () -- Best regards, Bulat mailto:bulatz@HotPOP.com