[Haskell-cafe] Factoring into type classes

[Daniel Fischer]

Am Montag, 19. Januar 2009 14:31 schrieb Antoine Latter:
> 2009/1/19 Luke Palmer <lrpalmer at gmail.com>:
> > 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.
>
> (,)  ?
>
> -Antoine

Wrong kind. And 
(,) a
has only one useful instance.