Re: [Haskell-cafe] Factoring into type classes

On Mon, Jan 19, 2009 at 3:58 AM, Patai Gergely wrote:

However, there are other type classes that are too general to assign such concrete uses to. For instance, if a data structure can have more than one meaningful (and useful) Functor or Monoid instance,

As a side curiosity, I would love to see an example of any data structure which has more than one Functor instance. Especially those which have more than one useful functor instance. Luke