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

   containers	Data.IntMap.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 :: (Key -> x -> Maybe y) -> SimpleWhenMissing x y
   

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

   but mapMaybeMissing uses fewer unnecessary Applicative operations.

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

   containers	Data.IntMap.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"
   

3. traverseMaybeMissing :: Applicative f => (Key -> x -> f (Maybe y)) -> WhenMissing f x y

   containers	Data.IntMap.Internal

   Traverse over the entries whose keys are missing from the other map, optionally producing values to put in the result. This is the most powerful WhenMissing tactic, but others are usually more efficient.

4. traverseMaybeWithKey :: Applicative f => (Key -> a -> f (Maybe b)) -> IntMap a -> f (IntMap b)

   containers	Data.IntMap.Internal

   Traverse keys/values and collect the Just results.

5. zipWithMaybeAMatched :: (Key -> x -> y -> f (Maybe z)) -> WhenMatched f x y z

   containers	Data.IntMap.Internal

   When a key is found in both maps, apply a function to the key and values, perform the resulting action, and maybe use the result in the merged map. This is the fundamental WhenMatched tactic.

6. zipWithMaybeMatched :: forall (f :: Type -> Type) x y z . Applicative f => (Key -> x -> y -> Maybe z) -> WhenMatched f x y z

   containers	Data.IntMap.Internal

   When a key is found in both maps, apply a function to the key and values and maybe use the result in the merged map.

   zipWithMaybeMatched
   :: (Key -> x -> y -> Maybe z)
   -> SimpleWhenMatched x y z
   

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

   containers	Data.IntMap.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"
   

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

   containers	Data.IntMap.Lazy

   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. traverseMaybeWithKey :: Applicative f => (Key -> a -> f (Maybe b)) -> IntMap a -> f (IntMap b)

   containers	Data.IntMap.Lazy

   Traverse keys/values and collect the Just results.

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

    containers	Data.IntMap.Merge.Lazy

    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 :: (Key -> x -> Maybe y) -> SimpleWhenMissing x y
    

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

    but mapMaybeMissing uses fewer unnecessary Applicative operations.

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