[Proposal] Add instance Monoid a => Monoid (Const a b)

[Herbert Valerio Riedel]

On 2013-09-29 at 18:01:23 +0200, haskell at nand.wakku.to wrote:

[...]

>> instance Monoid a => Monoid (Const a b) where
>>   mempty = Const mempty
>>   mappend (Const a) (Const b) = Const (mappend a b)

+1 from me


PS: As this proposal seems to be non-controversial so far, I've already
    added the instance in the soon-to-be `base-4.7.0.0`. Therefore,
    unless objections to this proposal should be voiced, this instance
    will be part of GHC 7.8.1's `base-4.7.0.0`.

Cheers,
  hvr