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1. mapMaybeWithKey :: (Key -> a -> Maybe b) -> IntMap a -> IntMap b

   containers	Data.IntMap.Strict

   Map keys/values and collect the Just results.

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

2. mapMaybe :: (a -> Maybe b) -> IntMap a -> IntMap b

   containers	Data.IntMap.Strict.Internal

   Map values and collect the Just results.

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

3. mapMaybeWithKey :: (Key -> a -> Maybe b) -> IntMap a -> IntMap b

   containers	Data.IntMap.Strict.Internal

   Map keys/values and collect the Just results.

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

4. mapMonotonic :: (Key -> Key) -> IntSet -> IntSet

   containers	Data.IntSet

   The 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 = toList s
   

5. mapMonotonic :: (Key -> Key) -> IntSet -> IntSet

   containers	Data.IntSet.Internal

   The 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 = toList s
   

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

   containers	Data.Map.Internal

   Map values and collect the Just results.

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

7. mapMaybeMissing :: forall (f :: Type -> Type) k x y . Applicative f => (k -> x -> Maybe y) -> WhenMissing f k x y

   containers	Data.Map.Internal

   Map over the entries whose keys are missing from the other map, optionally removing some. This is the most powerful SimpleWhenMissing tactic, but others are usually more efficient.

   mapMaybeMissing :: (k -> x -> Maybe y) -> SimpleWhenMissing k x y
   

   mapMaybeMissing f = traverseMaybeMissing (\k x -> pure (f k x))
   

   but mapMaybeMissing uses fewer unnecessary Applicative operations.

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

   containers	Data.Map.Internal

   Map keys/values and collect the Just results.

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

9. mapMissing :: forall (f :: Type -> Type) k x y . Applicative f => (k -> x -> y) -> WhenMissing f k x y

   containers	Data.Map.Internal

   Map over the entries whose keys are missing from the other map.

   mapMissing :: (k -> x -> y) -> SimpleWhenMissing k x y
   

   mapMissing f = mapMaybeMissing (\k x -> Just $ f k x)
   

   but mapMissing is somewhat faster.

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

    containers	Data.Map.Lazy

    Map values and collect the Just results.

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

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