suggestion: A common type class for mutable variables

[Bertram Felgenhauer]

Henning Thielemann wrote:
> On Mon, 3 Jun 2013, Edward Kmett wrote:
> 
> >The first option is
> >
> >class Monad m => MonadRef r m | m -> r where
> >  newRef :: a -> m (r a)
> >  ...
> 
> I thought the functional dependency should be the other way round:
> From the reference type to the monad where it lives in.

You can have it both ways.

class Monad m => RefM m r | m -> r, r -> m where
    -- | Create a new reference.
    newRef :: a -> m (r a)
    [...]

Cheers,

Bertram