On Mon, Jun 29, 2015 at 2:56 AM, Fumiaki Kinoshita <fumiexcel@gmail.com> wrote:

I found some missing instances in the base package. The instances below are almost unique by parametricity.

Data.Complex:
instance Functor Complex
instance Applicative Complex
instance Foldable Complex -- real first
instance Traversable Complex

I've had to have orphans for these in order to make linear work for years now. No objection to adding them. They were blocked before by the RealFloat a => data type context.

Data.Functor.Identity:
instance Monoid a => Monoid (Identity a)

Control.Applicative:
instance Foldable ZipList
instance Traversable ZipList

I'm going to write a patch if there is no issue with them.

Also, I wonder if () could be Storable:

instance Storable () where
sizeOf _ = 0
alignment _ = 1
peek _ = return ()
poke _ _ = return ()

No objection from me to any of them; a very strong +1.