Hoogle Search
Within LTS Haskell 24.36 (ghc-9.10.3)
Note that Stackage only displays results for the latest LTS and Nightly snapshot. Learn more.
maximumMaybe :: (Ord a, Foldable t) => t a -> Maybe ario RIO.List No documentation available.
minimumByMaybe :: Foldable t => (a -> a -> Ordering) -> t a -> Maybe ario RIO.List No documentation available.
minimumMaybe :: (Ord a, Foldable t) => t a -> Maybe ario RIO.List No documentation available.
-
rio RIO.List No documentation available.
mapMaybe :: (a -> Maybe b) -> Map k a -> Map k brio 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"
mapMaybeWithKey :: (k -> a -> Maybe b) -> Map k a -> Map k brio 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"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.
-
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]
forMaybeA :: Applicative f => [a] -> (a -> f (Maybe b)) -> f [b]rio RIO.Prelude forMaybeA == flip mapMaybeA
forMaybeM :: Monad m => [a] -> (a -> m (Maybe b)) -> m [b]rio RIO.Prelude forMaybeM == flip mapMaybeM