[GUI] get and set

[Sven Panne]

Krasimir Angelov wrote:
 > [...] Well! I expect future discussion in the libraries@haskell.org.
 > I propose to extract the type classes in the new module (maybe
 > Control.Monad.Attributes) and after that to add attribute types
 > along with their instances to modules which defines corresponding
 > monads. [...]

Just some last remarks before we *really* move this thread to the
libraries list:

* Is there a way to fit your proposal into the existing Control.Monad.*
   hierarchy by splitting MonadState into a read and a write part?

* Can we merge this somehow with Hughes' RefMonad?
   (http://www.math.chalmers.se/~rjmh/Globals.ps)

* The need for the functional dependencies is not 100% clear to me.

* Do we really need MPTC or can we get by with constructor classes
   somehow? This is a question I'm asking me from time to time in
   different contexts, too.

Due to a lack of time, I haven't spent much time thinking about these
issues for myself, but I think they should be clarified.

Cheers,
    S.