[containers] Proposal: Change to the Data.Map Monoid

[Henning Thielemann]

Am 19.05.2014 02:05, schrieb Nick Partridge:

> instance Monoid v => Monoid (Map k v) where
>      mappend = unionWith mappend
>
> This lets us build up maps with values in a useful Monoid, and mappend
> them with gusto.

This was discussed two years ago:
   http://www.haskell.org/pipermail/libraries/2012-April/017743.html

That said, I'd also prefer your instance.