suggestion: A common type class for mutable variables

[Henning Thielemann]

On Sun, 9 Jun 2013, Dominique Devriese wrote:

> Perhaps it's worth pointing out that one can avoid the functional
> dependencies (not the MPTCs) with a common API based on an explicit
> state dictionary: see code below. I would also personally find such an
> API more elegant, but I'm not sure others would agree with this.

It's nice! And you need the multi-parameter type class only if you want to 
use the MonadState class.