#4159: move Monad and MonadFix instances for Either from mtl to base

Edward Kmett ekmett at gmail.com
Tue Jun 29 07:49:01 EDT 2010


+1, and I'd vote again if I could!

On Tue, Jun 29, 2010 at 5:26 AM, Ross Paterson <ross at soi.city.ac.uk> wrote:

> The proposal is to move the Monad and MonadFix instances for Either
> (currently in the mtl package) to Control.Monad.Instances and
> Control.Monad.Fix respectively (both in the base package).  The Monad
> instance is still an orphan, to retain Haskell 98 compatibility, but the
> MonadFix instance is together with its class.  The Error constraint is
> removed from both instances, and the default definition of fail is used.
>
> Discussion deadline: 20th July 2010
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