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Within LTS Haskell 24.32 (ghc-9.10.3)

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

   strict	Data.Strict.Maybe

   Analogous to catMaybes in Data.Maybe.

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

   strict	Data.Strict.Maybe

   Given a default value and a Maybe, yield the default value if the Maybe argument is Nothing and extract the value out of the Just otherwise.

3. listToMaybe :: [a] -> Maybe a

   strict	Data.Strict.Maybe

   Analogous to listToMaybe in Data.Maybe.

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

   strict	Data.Strict.Maybe

   Analogous to mapMaybe in Data.Maybe.

5. combSpanMaybe :: SrcSpanInfo -> Maybe SrcSpanInfo -> SrcSpanInfo

   haskell-src-exts	Language.Haskell.Exts.SrcLoc

   Like (<+?>), but it also concatenates the srcInfoPoints.

6. contramapMaybe :: (a -> Maybe b) -> OutputStream b -> IO (OutputStream a)

   io-streams	System.IO.Streams.Combinators

   Contravariant counterpart to contramapMaybe. contramap f s passes all input to s through the function f. Discards all the elements for which f returns Nothing. Since: 1.2.1.0

7. 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

8. catMaybes :: (IsSequence (f (Maybe t)), Functor f, Element (f (Maybe t)) ~ Maybe t) => f (Maybe t) -> f t

   mono-traversable	Data.Sequences

   Takes all of the Just values from a sequence of Maybe ts and concatenates them into an unboxed sequence of ts. Since 0.6.2

9. leftToMaybe :: Either a b -> Maybe a

   either	Data.Either.Combinators

   Maybe get the Left side of an Either.

   leftToMaybe ≡ either Just (const Nothing)
   

   Using Control.Lens:

   leftToMaybe ≡ preview _Left
   leftToMaybe x ≡ x^?_Left
   

   >>> leftToMaybe (Left 12)
   Just 12
   

   >>> leftToMaybe (Right 12)
   Nothing
   

10. rightToMaybe :: Either a b -> Maybe b

    either	Data.Either.Combinators

    Maybe get the Right side of an Either.

    rightToMaybe ≡ either (const Nothing) Just
    

    Using Control.Lens:

    rightToMaybe ≡ preview _Right
    rightToMaybe x ≡ x^?_Right
    

    >>> rightToMaybe (Left 12)
    Nothing
    

    >>> rightToMaybe (Right 12)
    Just 12
    

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