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Within LTS Haskell 24.4 (ghc-9.10.2)

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  1. maybeAt :: Int -> [a] -> Maybe a

    relude Relude.List

    !!? with its arguments flipped. Get element from list using index value starting from `0`. 

    >>> maybeAt 0 []
Nothing

    >>> maybeAt 3 ["a", "b", "c"]
Nothing

    >>> maybeAt (-1) [1, 2, 3]
Nothing

    >>> maybeAt 2 ["a", "b", "c"]
Just "c"

  2. maybeToLeft :: r -> Maybe l -> Either l r

    relude Relude.Monad.Either

    Maps Maybe to Either wrapping default value into Right. 

    >>> maybeToLeft True (Just "aba")
Left "aba"

>>> maybeToLeft True Nothing
Right True

  3. maybeToRight :: l -> Maybe r -> Either l r

    relude Relude.Monad.Either

    Maps Maybe to Either wrapping default value into Left. 

    >>> maybeToRight True (Just "aba")
Right "aba"

>>> maybeToRight True Nothing
Left True

  4. maybeToExceptT :: forall (m :: Type -> Type) e a . Functor m => e -> MaybeT m a -> ExceptT e m a

    relude Relude.Monad.Reexport

    Convert a MaybeT computation to ExceptT, with a default exception value.

  5. maybeToList :: Maybe a -> [a]

    relude Relude.Monad.Reexport

    The maybeToList function returns an empty list when given Nothing or a singleton list when given Just.

    Examples

    Basic usage: 
    >>> maybeToList (Just 7)
[7]

    >>> maybeToList Nothing
[]
    One can use maybeToList to avoid pattern matching when combined with a function that (safely) works on lists: 
    >>> import GHC.Internal.Text.Read ( readMaybe )

>>> sum $ maybeToList (readMaybe "3")
3

>>> sum $ maybeToList (readMaybe "")
0

  6. maybeToMonoid :: Monoid m => Maybe m -> m

    relude Relude.Monoid

    Extracts Monoid value from Maybe returning mempty if Nothing. 

    >>> maybeToMonoid (Just [1,2,3] :: Maybe [Int])
[1,2,3]

>>> maybeToMonoid (Nothing :: Maybe [Int])
[]

  7. maybeF :: Buildable a => Maybe a -> Builder

    fmt Fmt

    Like build for Maybe, but displays Nothing as <Nothing> instead of an empty string. build: 

    >>> build (Nothing :: Maybe Int)
""

>>> build (Just 1 :: Maybe Int)
"1"
    maybeF: 
    >>> maybeF (Nothing :: Maybe Int)
"<Nothing>"

>>> maybeF (Just 1 :: Maybe Int)
"1"

  8. maybeF :: Buildable a => Maybe a -> Builder

    fmt Fmt.Internal.Formatters

    Like build for Maybe, but displays Nothing as <Nothing> instead of an empty string. build: 

    >>> build (Nothing :: Maybe Int)
""

>>> build (Just 1 :: Maybe Int)
"1"
    maybeF: 
    >>> maybeF (Nothing :: Maybe Int)
"<Nothing>"

>>> maybeF (Just 1 :: Maybe Int)
"1"

  9. maybeRead :: Read a => String -> Maybe a

    ghc-boot GHC.Settings.Utils

    No documentation available.

  10. maybeReadFuzzy :: Read a => String -> Maybe a

    ghc-boot GHC.Settings.Utils

    No documentation available.

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