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Within LTS Haskell 24.32 (ghc-9.10.3)

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1. lastMaybe :: [a] -> Maybe a

   rio	RIO.List

   No documentation available.

2. maximumByMaybe :: Foldable t => (a -> a -> Ordering) -> t a -> Maybe a

   rio	RIO.List

   No documentation available.

3. maximumMaybe :: (Ord a, Foldable t) => t a -> Maybe a

   rio	RIO.List

   No documentation available.

4. minimumByMaybe :: Foldable t => (a -> a -> Ordering) -> t a -> Maybe a

   rio	RIO.List

   No documentation available.

5. minimumMaybe :: (Ord a, Foldable t) => t a -> Maybe a

   rio	RIO.List

   No documentation available.

6. tailMaybe :: [a] -> Maybe [a]

   rio	RIO.List

   No documentation available.

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

   rio	RIO.Map

   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 :: (k -> a -> Maybe b) -> Map k a -> Map k b

   rio	RIO.Map

   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 => (k -> a -> f (Maybe b)) -> Map k a -> f (Map k b)

   rio	RIO.Map

   Traverse keys/values and collect the Just results.

10. catMaybes :: [Maybe a] -> [a]

    rio	RIO.Prelude

    The catMaybes function takes a list of Maybes and returns a list of all the Just values.

    Examples

    Basic usage:

    >>> catMaybes [Just 1, Nothing, Just 3]
    [1,3]
    

    When constructing a list of Maybe values, catMaybes can be used to return all of the "success" results (if the list is the result of a map, then mapMaybe would be more appropriate):

    >>> import GHC.Internal.Text.Read ( readMaybe )
    
    >>> [readMaybe x :: Maybe Int | x <- ["1", "Foo", "3"] ]
    [Just 1,Nothing,Just 3]
    
    >>> catMaybes $ [readMaybe x :: Maybe Int | x <- ["1", "Foo", "3"] ]
    [1,3]
    

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