IntMap.differenceKeysSet for removing an IntSet of keys

[liyang]

Currently, IntMap.difference ma mb removes all the keys in mb from ma, where the elements of the two IntMaps can be of different types; the elements of mb are not used.

There is no efficient way to remove an IntSet of keys, however. These patches adds the IntMap.differenceKeysSet function—essentially a copy/paste of difference—that satisfies the following property:

prop_DiffKeysSet :: Map Int -> Map () -> Bool
prop_DiffKeysSet t1 t2
  = difference t1 t2 == differenceKeysSet t1 (keysSet t2)

[liyang]

forgot to export differenceKeysSet

[milan]

Hi,

I am closing the proposal. The representation of IntSet? has changed in the development version of containers and no longer corresponds 1:1 to IntMap?. The patch could be modified to reflect this, but I do not believe the differenceKeysSet method is worth fiddling with IntSet? internals in IntMap? module.

FYI, Data.IntMap?.fromSet will be provided in the new version of containers. So it will be possible to do IntMap?.difference map (fromSet (const ()) set).

Cheers, Milan