Adding a newtype EndoCategory to Control.Category (ticket #3362)

roconnor at roconnor at
Thu Jul 9 09:13:22 EDT 2009

On Thu, 9 Jul 2009, Ross Paterson wrote:

> On Wed, Jul 08, 2009 at 10:05:31PM -0400, roconnor at wrote:
>>> The only packages on hackage containing instances for Endo are:
>>>  base
>>>  HStringTemplate
>>>  monoids
>>>  special-functors
>>>  TypeCompose
>> Is this few enough that we can make our change?
> The following additional packages use the current structure of Endo,
> which would change:
> ...

Would they really need to change if we did

newtype Endomorph a x = Endo { getEndo :: a x x }

type Endo = Endomorph (->)

I guess it would be kinda confusing if we did that. ... but only a little. 

Russell O'Connor                                      <>
``All talk about `theft,''' the general counsel of the American Graphophone
Company wrote, ``is the merest claptrap, for there exists no property in
ideas musical, literary or artistic, except as defined by statute.''

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