Add meaningful instances to ZipList

[wren ng thornton]

On 12/17/11 1:37 PM, Daniel Peebles wrote:
> I noticed that the ZipList newtype in Control.Applicative has no derived
> instances at all. We can't show a ZipList, check it for equality, or do
> anything to it except unpack it or treat it like an Applicative or Functor.
>
> It seems fairly uncontroversial to suggest adding some instances for it,
> but there are some minor questions to address: the obvious instances to add
> might be Eq, Ord, Show, Read, and possibly Typeable and/or Data.

+1 btw.

-- 
Live well,
~wren