Hello all, I found myself writing this piece of code: -- | Create and add a new 'Item' to the system sysAddItem :: ItmLabel -> ItmVolume -> ItmCapacity -> Position -> Instant -> State System ItmId sysAddItem lbl vol cap pos t = do sys <- get id <- sysNextId :: State System Id itms' <- return $ execState (itmAdd' (Itm id lbl vol cap pos t)) (sysItems sys) --** modify (\sys -> sys{sysItems=itms'}) return id In the lonely line ** in the middle I use itmAdd' :: Item -> State ItemDb (), where the ItemDb is part of the 'System' and can be extracted via sysItems. I believe this code is correct, but I don't like it. The expression to the right of <- must have the type State System ItemDb But ItemAdd' has the type Item -> State ItemDb () So I need to transform (Item -> State ItemDb ()) to (State System ItemDb). There is no question that I have to pass the Item, but the transformation of the States is quite noisy. Is there a better way to make this transformation, given a function System->ItemDb (i.e. sysItems)?