suggestion: A common type class for mutable variables

[Henning Thielemann]

On Thu, 30 May 2013, Petr Pudlák wrote:

> I've found that there is a package that provides such a type class:
> http://hackage.haskell.org/package/reference

> I'd suggest to add similar functionality to base, perhaps with some different 
> wording - I'd rather use Data.MRef (as "mutable reference").

There are more such packages:
    http://hackage.haskell.org/package/stateref
    http://hackage.haskell.org/package/monad-statevar
    http://hackage.haskell.org/package/ref-fd
    http://hackage.haskell.org/package/ref-tf
    http://hackage.haskell.org/package/ref-mtl