different flavours of Monad Template Library

[Henning Thielemann]

On Mon, 5 Jan 2009, Ross Paterson wrote:

> On Mon, Jan 05, 2009 at 01:07:00AM +0100, Henning Thielemann wrote:
>
>> At least 'transformers' seems to be distinct enough from current MTL
>> and simple enough to be uploaded to Hackage right now.
>
> OK, I've done that.
>
>> However, Control.Monad.Identity would conflict with MTL.
>
> Unfortunately that is necessary to make the split work.  If we have
> a monad-classes-fd package, clients would have to depend on both it
> and transformers.

How about Control.Monad.Trans.Identity which is re-exported by 
Control.Monad.Identity in mtl?

I also like to have a function 'state', which replaces the former 'State' 
constructor. I can also submit a patch if you want that.