different flavours of Monad Template Library

Henning Thielemann lemming at henning-thielemann.de
Mon Jan 5 06:54:20 EST 2009

On Mon, 5 Jan 2009, Ross Paterson wrote:

> On Mon, Jan 05, 2009 at 09:32:21AM +0100, Henning Thielemann wrote:
>> How about Control.Monad.Trans.Identity which is re-exported by
>> Control.Monad.Identity in mtl?
> Hmm, it's a conflict between co-existing with mtl and using the
> Right Name for the transformers package, which is intended to be
> usable by itself.  I prefer the latter, myself.

You mean that Control.Monad.Trans.Identity is not a good name, because 
Identity is not a transformer? Then, how about 
Control.Monad.Base.Identity, Control.Monad.Primitive.Identity or so?

Since mtl-split is not a drop-in replacement for mtl, we cannot expect a 
quick change from mtl to mtl-split in all the packages that currently 
import mtl. Thus we have to think about a route of transition and a 
package which can be installed in parallel to mtl is a first step, I 

>> I also like to have a function 'state', which replaces the former 
>> 'State' constructor. I can also submit a patch if you want that.
> You mean
> 	state :: (s -> (a, s)) -> State s a
> 	state f = StateT (Identity . f)
> and similarly for all the others?  Sounds reasonable.

That's what I mean.

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