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Within LTS Haskell 24.39 (ghc-9.10.3)

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

   containers	Data.Map.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"
   

2. mapWithKey :: (k -> a -> b) -> Map k a -> Map k b

   containers	Data.Map.Lazy

   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")]
   

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

   containers	Data.Map.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 :: (k -> x -> Maybe y) -> SimpleWhenMissing k x y
   

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

   but mapMaybeMissing uses fewer unnecessary Applicative operations.

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

   containers	Data.Map.Merge.Lazy

   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.

5. mapWhenMatched :: forall (f :: Type -> Type) a b k x y . Functor f => (a -> b) -> WhenMatched f k x y a -> WhenMatched f k x y b

   containers	Data.Map.Merge.Lazy

   Map covariantly over a WhenMatched f k x y.

6. mapWhenMissing :: forall (f :: Type -> Type) a b k x . (Applicative f, Monad f) => (a -> b) -> WhenMissing f k x a -> WhenMissing f k x b

   containers	Data.Map.Merge.Lazy

   Map covariantly over a WhenMissing f k x.

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

   containers	Data.Map.Merge.Strict

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

   containers	Data.Map.Merge.Strict

   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.

9. mapWhenMatched :: forall (f :: Type -> Type) a b k x y . Functor f => (a -> b) -> WhenMatched f k x y a -> WhenMatched f k x y b

   containers	Data.Map.Merge.Strict

   Map covariantly over a WhenMatched f k x y.

10. mapWhenMissing :: forall (f :: Type -> Type) a b k x . Functor f => (a -> b) -> WhenMissing f k x a -> WhenMissing f k x b

    containers	Data.Map.Merge.Strict

    Map covariantly over a WhenMissing f k x.

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