I'm a very strong +1 on this.

We've already sat down to add some of these, and there was a general resolution by the core libraries committee in response to a similar raised issue for the types in GHC.Generics that missing instances like this that have obvious canonical implementations should be added wherever possible.

-Edward

On Fri, Dec 12, 2014 at 2:30 AM, Sean Leather <sean.leather@gmail.com> wrote:
As of base 4.7.0.1, none of the newtype wrappers in Data.Monoid have instances for:
  • Typeable
  • Data
  • Functor

It looks like the base library repository has AutoDeriveTypeable, so I presume that takes care of the Typeable instances. It also looks like First and Last now have Functor instances, amongst others.

In particular, I would like to add Functor instances for all parameterized types, where applicable (i.e. Dual, Sum, Product).

In general, I think we should add whatever other instances make sense. Data came to mind. Others?

Discussion period: 2 weeks (or perhaps until after the beginning of the new year)

Regards,
Sean

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