Ryan: I'm proposing not moving Data.Functor.Constant at all and leaving that module alone, unmoved.

I'm proposing rather adding Data.Functor.Const and having Control.Applicative re-export Const from it rather than supply its own.

This allows us to follow the general pattern of having all the data types available on display in the Data.Functor.* hierarchy, while still allowing for the fact that Const won the convenience war a long time ago.

This avoids breaking any of the handful of users of the current Constant data type, which could then be gracefully deprecated -- or not as Ross sees fit, within his purview as the maintainer of the transformers package.

-Edward

On Thu, Jul 23, 2015 at 11:13 PM, Ryan Scott <ryan.gl.scott@gmail.com> wrote:

I really like this proposal, especially since having convenient Eq1,
Ord1, Read1, Show1, etc. instances is something I've wanted for a
while.

I have some questions about some specifics:

1. Just to verify, you're proposing a breaking change in which
Data.Functor.Constant no longer exports Constant, but rather Const?
2. You mentioned that the additions to base could use
DefaultSignatures. Could you give an example of how this would work?
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