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1. mapKeysWith :: Ord k2 => (a -> a -> a) -> (k1 -> k2) -> NEMap k1 a -> NEMap k2 a

   nonempty-containers	Data.Map.NonEmpty

   O(n*log n). mapKeysWith c f s is the map obtained by applying f to each key of s. The size of the result may be smaller if f maps two or more distinct keys to the same new key. In this case the associated values will be combined using c. The value at the greater of the two original keys is used as the first argument to c. While the size of the result map may be smaller than the input map, the output map is still guaranteed to be non-empty if the input map is non-empty.

   mapKeysWith (++) (\ _ -> 1) (fromList ((1,"b") :| [(2,"a"), (3,"d"), (4,"c")])) == singleton 1 "cdab"
   mapKeysWith (++) (\ _ -> 3) (fromList ((1,"b") :| [(2,"a"), (3,"d"), (4,"c")])) == singleton 3 "cdab"
   

2. mapMaybe :: (a -> Maybe b) -> NEMap k a -> Map k b

   nonempty-containers	Data.Map.NonEmpty

   O(n). Map values and collect the Just results. Returns a potentially empty map (Map), because the function could potentially return Nothing on all items in the NEMap.

   let f x = if x == "a" then Just "new a" else Nothing
   mapMaybe f (fromList ((5,"a") :| [(3,"b")])) == Data.Map.singleton 5 "new a"
   

3. mapMaybeWithKey :: (k -> a -> Maybe b) -> NEMap k a -> Map k b

   nonempty-containers	Data.Map.NonEmpty

   O(n). Map keys/values and collect the Just results. Returns a potentially empty map (Map), because the function could potentially return Nothing on all items in the NEMap.

   let f k _ = if k < 5 then Just ("key : " ++ (show k)) else Nothing
   mapMaybeWithKey f (fromList ((5,"a") :| [(3,"b")])) == Data.Map.singleton 3 "key : 3"
   

4. mapWithKey :: (k -> a -> b) -> NEMap k a -> NEMap k b

   nonempty-containers	Data.Map.NonEmpty

   O(n). Map a function over all values in the map.

   let f key x = (show key) ++ ":" ++ x
   mapWithKey f (fromList ((5,"a") :| [(3,"b")])) == fromList ((3, "3:b") :| [(5, "5:a")])
   

5. mapWithIndex :: (Int -> a -> b) -> NESeq a -> NESeq b

   nonempty-containers	Data.Sequence.NonEmpty

   A generalization of fmap, mapWithIndex takes a mapping function that also depends on the element's index, and applies it to every element in the sequence.

6. mapMonotonic :: (a -> b) -> NESet a -> NESet b

   nonempty-containers	Data.Set.NonEmpty

   O(n). mapMonotonic f s == map f s, but works only when f is strictly increasing. The precondition is not checked. Semi-formally, we have:

   and [x < y ==> f x < f y | x <- ls, y <- ls]
   ==> mapMonotonic f s == map f s
   where ls = Data.Foldable.toList s
   

7. mappingNamer :: (String -> [String]) -> FieldNamer

   optics-th	Optics.TH

   Create a FieldNamer from a mapping function. If the function returns [], it creates no lens for the field.

8. mapToDMap :: Map k v -> DMap (Const2 k v) Identity

   patch	Data.Functor.Misc

   Convert a regular Map to a DMap

9. mapIntMapPatchWithKey :: (Int -> a -> b) -> PatchIntMap a -> PatchIntMap b

   patch	Data.Patch

   Map a function Int -> a -> b over all as in the given PatchIntMap a (that is, all inserts/updates), producing a PatchIntMap b.

10. mapIntMapPatchWithKey :: (Int -> a -> b) -> PatchIntMap a -> PatchIntMap b

    patch	Data.Patch.IntMap

    Map a function Int -> a -> b over all as in the given PatchIntMap a (that is, all inserts/updates), producing a PatchIntMap b.

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