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

Iavor Diatchki iavor.diatchki at gmail.com
Fri Jul 16 03:58:39 EDT 2010

I am against adding the instances for Monad Either to the base package
for the same reasons as the ones in the thread "proposal #4095: add
Applicative instance for Either".

On Wed, Jul 7, 2010 at 6:06 PM, Edward Z. Yang <ezyang at mit.edu> wrote:
> Excerpts from Isaac Dupree's message of Fri Jul 02 12:25:33 -0400 2010:
>> It's not quite as simple as that -- as soon as we start making Either an
>> instance of kind (* -> *) classes, such as Functor and Monad, there
>> inevitably becomes some kind of semantic difference between Left and Right.
> Right, so what we end up with is short-circuiting computation with different
> results.
> Cheers,
> Edward
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