[Haskell-cafe] converting IOException to Either in ErrorT

I wrote this to make it a little nicer to catch IO exceptions and convert them to ErrorT failure: onExceptionThrowError :: (Error ce) => IO a -> (String -> ce) -> ErrorT ce IO a onExceptionThrowError a ce = liftIO (try a) >>= either (\(e :: IOException) -> throwError (ce (show e))) return So now I can do, e.g., writeFile fp s `onExceptionThrowError` SpecificErrorConstructor ... It works, but seems bad. Please let me know if you see ways to improve it. Thanks.