[Haskell-beginners] Functor instance

[Sumit Raja]

> I'm trying to implement my own Result type (and yes, I'm aware you can
> abuse Either for this :-) ) but doing something as (seemingly?) simple
> as implementing a Functor instance was surprisingly difficult.
>
Without knowing your final use case are Bifunctors what you are after
(https://hackage.haskell.org/package/base-4.10.1.0/docs/Data-Bifunctor.html)?
I used them when I wanted to fmap Left to convert errors to other
errors.

-Sumit