I have looked at the recently released Control.Failure library but I admit, I couldn't understand it completely. So given the example below, how would Control.Failure help me here? Thanks, nt -- Theirs (other library code stubs) data TheirError = TheirErrorCase deriving Show data TheirData = TheirData deriving Show theirFunc :: [String] -> Either TheirError TheirData theirFunc = undefined -- Mine (my own code stubs) data MyError = MyErrorCase deriving Show data MyData = MyData deriving Show myFuncA :: TheirData -> Either MyError MyData myFuncA = undefined -- Ugly. How to apply Control.Failure here? myFuncB :: IO (Either MyError MyData) myFuncB = do let x = theirFunc [] case x of Right x' -> return $ myFuncA x' Left _ -> return . Left $ MyErrorCase