On 17 августа 2012 11:48:54 Magicloud Magiclouds wrote:

> But how if here maybe[ABC] are like 'IO (Maybe Int)', or foo is type

> of 'Int -> IO Int'?

Maybe you can help monad transformers and MaybeT? They help you write code like 'MaybeT f1 >> MaybeT f2 >> MaybeT f3 where { f1, f2, f3 :: IO (Maybe Int) }'.