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1. mapMaybe :: (a -> Maybe b) -> Word64Map a -> Word64Map b

   ghc	GHC.Data.Word64Map.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"
   

2. mapMaybe :: (a -> Maybe b) -> Word64Map a -> Word64Map b

   ghc	GHC.Data.Word64Map.Strict

   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. mapMaybe :: (a -> Maybe b) -> Word64Map a -> Word64Map b

   ghc	GHC.Data.Word64Map.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"
   

4. mapMaybe :: forall (m :: Type -> Type) a b r . Functor m => (a -> Maybe b) -> Pipe a b m r

   pipes	Pipes.Prelude

   (mapMaybe f) yields Just results of f. Basic laws:

   mapMaybe (f >=> g) = mapMaybe f >-> mapMaybe g
   
   mapMaybe (pure @Maybe . f) = mapMaybe (Just . f) = map f
   
   mapMaybe (const Nothing) = drain
   

   As a result of the second law,

   mapMaybe return = mapMaybe Just = cat
   

5. mapMaybe :: (a -> Maybe b) -> CharMap a -> CharMap b

   regex-tdfa	Data.IntMap.CharMap2

   No documentation available.

6. mapMaybe :: Enum key => (a -> Maybe b) -> EnumMap key a -> EnumMap key b

   regex-tdfa	Data.IntMap.EnumMap2

   No documentation available.

7. mapMaybe :: Ord key => key -> T (Map key elem) (Maybe elem)

   data-accessor	Data.Accessor.Container

   Treats a finite map like an infinite map, where all undefined elements are Nothing and defined elements are Just.

8. mapMaybe :: (a -> Maybe b) -> InputStream a -> IO (InputStream b)

   io-streams	System.IO.Streams.Combinators

   A version of map that discards elements mapMaybe f s passes all output from s through the function f and discards elements for which f s evaluates to Nothing. Example:

   ghci> Streams.fromList [Just 1, None, Just 3] >>=
   Streams.mapMaybe id >>=
   Streams.toList
   [1,3]
   

   Since: 1.2.1.0

9. mapMaybe :: (a -> Maybe b) -> [a] -> [b]

   strict	Data.Strict.Maybe

   Analogous to mapMaybe in Data.Maybe.

10. mapMaybe :: (v1 -> Maybe v2) -> HashMap k v1 -> HashMap k v2

    rio	RIO.HashMap

    Transform this map by applying a function to every value and retaining only some of them.

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