[Haskell-cafe] Monad.Reader with updates

Hi, Is there some abstraction in current ghc library that implements something like Reader, but where the value of the environment is updated at every "step"? I imagine something that instead of running like this: runReader ( do ... ) environment I would run like: runReader ( do ... ) environment update_function So, when I write a monad like: do a <- asks f b <- asks f2 c <- asks f3 f, f2 and f3 would be called with parameters environment, (update_function environment), (update_function . updatefunction $ environment) etc. Does that make sense? Is it easy to adapt something already existing to do that? Thanks, Maurício