Hi, I've defined a class and some instances, which I'm hoping would help me "show" values of types that may include transactional elements. class TShow a where tshow :: a -> IO String instance Show (TVar a) where show = "%" instance (Show a) => TShow a where tshow a = return $ show a instance (Show a) => TShow (TVar a) where tshow ta = do a <- readTVar ta return $ show a Having created a new class is it possible to do some magic so that it can be put it into a deriving clause? data Type = Type { field1 :: Int , field2 :: Int } deriving Show data AnotherType = AnotherType { field3 :: Int , field4 :: TVar Type } deriving *TShow* Thanks -John