+1, seems reasonable. Edward Excerpts from wren ng thornton's message of Mon Apr 30 01:33:39 -0400 2012:
Hello all,
I recently (re)noticed the following duplication:
base:Control.Applicative newtype Const a b = Const { getConst :: a } instance Functor (Const m) where... instance Monoid m => Applicative (Const m) where...
transformers:Data.Functor.Constant newtype Constant a b = Constant { getConstant :: a } instance Functor (Constant a) where... instance Foldable (Constant a) where... instance Traversable (Constant a) where... instance (Monoid a) => Applicative (Constant a) where...
I don't see any reason for this redundancy. I propose we:
(1) add the Foldable and Traversable instances to base, and (2) deprecate transformers:Data.Functor.Constant
This will cause breakage to any orphan instances of Foldable/Traversable for Const, but that seems fine by me. Eventually we'll want to remove transformers:Data.Functor.Constant (or have it re-export the Const stuff from base:Control.Applicative); but that can be handled later.
Deadline: 14 May 2012.