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

[David Feuer]

If you name it, it will come!

On Jul 14, 2016 11:55 AM, "Ross Paterson" <R.Paterson at city.ac.uk> wrote:

> On Thu, Jul 14, 2016 at 12:45:27AM -0400, David Feuer wrote:
> > Cale Gibbard proposes the following:
> >
> > Data.IntMap.restriction :: IntSet -> IntMap a -> IntMap a
> > Data.Map.restriction :: Ord k => Set k -> Map k a -> Map k a
> >
> > In each case, the map is filtered to contain only the keys that are
> > also found in the set. This can be implemented efficiently using a
> > slightly stripped-down version of Data.Map.intersection.
>
> One might also want the counterpart of Data.Map.difference for similar
> reasons.
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