Proposal: Add `restriction` to Data.Map and Data.IntMap

[Evan Laforge]

On Thu, Jul 14, 2016 at 8:01 AM, Iavor Diatchki
<iavor.diatchki at gmail.com> wrote:
> I've also needed this in the past, so +1.
>
> I think the bike-shed should be colored:  intersectKeys or restrictKeys

+1 for intersectKeys.  I already have to look up Data.Map haddock
constantly (e.g. alter vs. adjust), but intersectKeys is nicely self
descriptive.