-1, I'm against breaking the current Monoid also.

I like Gabriel's solutions, and particularly I'd like to have:

instance (Ord k, Semigroup v) => Monoid (WrappedMap k v) where
    mempty            = empty
    mappend map0 map1 = unionWith <> map0 map1
    mconcat maps      = foldr (unionWith <>) empty maps

but even a Monoid constraint would be useful.

John L.


On Wed, Mar 13, 2013 at 12:59 AM, Gabriel Gonzalez <gabriel439@gmail.com> wrote:
-1 on breaking the existing Monoid instance.  I'd prefer either:

a) A newtype for the additional Monoid instance, or
b) providing an associative operator equivalent to the new Monoid instance

I'm not convinced that the replacement instance is more useful, let alone useful enough to break everything depending on containers.  A lot of packages both on and off Hackage depend on Edward's code, almost all of which would break as a result of this change.


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