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Within LTS Haskell 24.39 (ghc-9.10.3)

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1. fromMaybeMM :: Monad m => m a -> m (Maybe a) -> m a

   from-sum	Control.FromSum

   Similar to fromMaybeM but the Maybe argument is also a monadic value.

   >>> fromMaybeMM [] [Just 6, Just 5]
   [6,5]
   
   >>> fromMaybeMM [] [Just 6, Nothing, Just 7]
   [6,7]
   

   NOTE: I don't particularly like the name of this function. If you have a suggestion for a better name, please submit a PR or issue.

2. fromMaybeM_ :: (Applicative m, Monoid b) => m b -> Maybe a -> m b

   from-sum	Control.FromSum

   Similar to fromMaybeM, but only run the monadic nothingAction if the Maybe argument is Nothing. Otherwise, return pure mempty.

   fromMaybeM_ nothingAction === maybe nothingAction (const $ pure mempty)
   

   >>> fromMaybeM_ (putStrLn "hello" >> pure "bye") $ Just 5
   ""
   
   >>> fromMaybeM_ (putStrLn "hello" >> pure "bye") Nothing
   hello
   "bye"
   

   This can be convenient when you want to run some sort of logging function whenever a Maybe is Nothing. If you imagine the logging function is IO (), then the effective type of fromMaybeM_ becomes fromMaybeM_ :: IO () -> Maybe a -> IO (), because () has a Monoid instance, and IO, has an Applicative instance.

   >>> fromMaybeM_ (putStrLn "hello") Nothing
   hello
   

3. fromMaybeOr :: Maybe a -> a -> a

   from-sum	Control.FromSum

   A fliped version of fromMaybe.

4. fromMaybeOrExceptT :: forall (m :: Type -> Type) a x . Monad m => Maybe a -> x -> ExceptT x m a

   from-sum	Control.FromSum

   Just like fromMaybeExceptT but with the arguments flipped.

5. fromMaybeOrM :: Applicative m => Maybe a -> m a -> m a

   from-sum	Control.FromSum

   A fliped version of fromMaybeM.

   >>> fromMaybeOrM (Just 5) []
   [5]
   

   This can be nice to use as an error handler.

   >>> fromMaybeOrM (Just 5) $ putStrLn "some error occurred" >> undefined
   5
   
   >>> fromMaybeOrM (Nothing) $ putStrLn "some error occurred" >> undefined
   some error occurred
   ...
   

6. fromMaybeOrMExceptT :: Monad m => m (Maybe a) -> x -> ExceptT x m a

   from-sum	Control.FromSum

   Just like fromMaybeMExceptT but with the arguments flipped.

7. fromMaybeOrMM :: Monad m => m (Maybe a) -> m a -> m a

   from-sum	Control.FromSum

   A fliped version of fromMaybeMM.

8. fromMaybeOrM_ :: (Applicative m, Monoid b) => Maybe a -> m b -> m b

   from-sum	Control.FromSum

   A fliped version of fromMaybeM.

9. parseFrontmatterMaybe :: ByteString -> Maybe ByteString

   frontmatter	Data.Frontmatter

   parseFrontmatter but returning a Maybe

10. parseYamlFrontmatterMaybe :: FromJSON a => ByteString -> Maybe a

    frontmatter	Data.Frontmatter

    parseYamlFrontmatter but returning a Maybe

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