:: (a -> m (Maybe b)) -> [a] -> m [b] -package:monad-extras

A version of mapMaybe that works with a monadic predicate.

The monadic version of the mapMaybe function.

>>> :{
evenInHalf :: Int -> IO (Maybe Int)
evenInHalf n
| even n = pure $ Just $ n `div` 2
| otherwise = pure Nothing
:}

>>> mapMaybeM evenInHalf [1..10]
[1,2,3,4,5]

Monadic mapMaybe.

A monadic version of mapMaybe :: (a -> Maybe b) -> [a] -> [b].

Applicative version of mapMaybe

Applicative mapMaybe.

Map each element to a Maybe monoidal and sequence the results (like traverse and mapMaybe).

O(n) Apply the monadic function to each element of the vector and discard elements returning Nothing.

forMaybeA == flip mapMaybeA

forMaybeM == flip mapMaybeM

The for version of mapMaybeM.