On 2017-07-07 12:48 AM, Clinton Mead wrote:

Consider the illustrative code below:
...
    class MyFunctor f where
       myFmap :: (forall a. t a -> u a) -> f t -> f u
...


Basically this is a sort of "higher order" functor, but I can't seem to fit it into an ordinary functor.

But it seems like I'm reinventing the wheel, as my code is suspiciously like `Functor` but only slightly different.

Has this sort of class already been created and if so what package is it in?

Yes, I have recently created rank2classes package:

   http://hackage.haskell.org/package/rank2classes

        Apart from the mirror-universe Functor class, the package exports the Applicative, Foldable, Traversable, Applicative, and Distributive classes, as well as some Template Hashell to derive some of their instances automatically.

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