-- | /O(n*min(n,W))/. The set of all keys of the map.
--
-- > keysSet (fromList [(5,"a"), (3,"b")]) == Data.IntSet.fromList [3,5]
-- > keysSet empty == Data.IntSet.empty
keysSet :: IntMap a -> Data.IntSet.IntSet
keysSet = Data.IntSet.fromDistinctAscList . keys
keysSet :: IntMap a -> Data.IntSet.IntSet
keysSet = Data.IntSet.fromDistinctAscList . keys
keysSet = Data.IntSet.fromDistinctAscList . keys