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Within LTS Haskell 24.65 (ghc-9.10.3)

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1. tryMaybeT :: IO a -> MaybeT IO a

   ghc-lib-parser	GHC.Data.Maybe

   Try performing an IO action, failing on error.

2. fromMaybe :: a -> Maybe a -> a

   ghc-lib-parser	GHC.Data.Strict

   No documentation available.

3. filterMaybe :: (a -> Bool) -> Maybe a -> Maybe a

   ghc-lib-parser	GHC.Data.TrieMap

   No documentation available.

4. foldMaybe :: (a -> b -> b) -> Maybe a -> b -> b

   ghc-lib-parser	GHC.Data.TrieMap

   No documentation available.

5. apMaybeUB :: MaybeUB (a -> b) -> MaybeUB a -> MaybeUB b

   ghc-lib-parser	GHC.Data.Unboxed

   No documentation available.

6. fmapMaybeUB :: (a -> b) -> MaybeUB a -> MaybeUB b

   ghc-lib-parser	GHC.Data.Unboxed

   No documentation available.

7. fromMaybeUB :: a -> MaybeUB a -> a

   ghc-lib-parser	GHC.Data.Unboxed

   No documentation available.

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

   ghc-lib-parser	GHC.Data.Word64Map.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"
   

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

   ghc-lib-parser	GHC.Data.Word64Map.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.

10. mapMaybeWithKey :: (Key -> a -> Maybe b) -> Word64Map a -> Word64Map b

    ghc-lib-parser	GHC.Data.Word64Map.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"
    

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