Hi, I wrote some code and I want to refactor it to use the Error monad combined with IO operations. I found some examples of monad transformers but I didn't really get them. So I have a function in IO monad which does several operations which might fail. These operations work with files so they have to be in IO monad but on the other hand I would like to use Error monad such that I can throw errors. So far I came up with something like this. data Config = Config { root :: String } data ParsedData = ParsedData {...} data MyError = ConfigError | ParseError | OtherError String instance Error MyError where strMsg = OtherError loadConfig :: String -> Either MyError (IO Config) loadConfig fn -> ...might throwError ConfigError parseFile :: String -> Either MyError (IO ParsedData) parseFile fn -> .. might throwError ParseError main -> do config <- loadConfig "mycfg.cfg" parsedData <- parseFile (root config) ... Can somebody please enlighten me about how to apply monad transformers in this situation? Thanks, Ovidiu