Hoogle Search
Within LTS Haskell 24.41 (ghc-9.10.3)
Note that Stackage only displays results for the latest LTS and Nightly snapshot. Learn more.
mapMaybe :: forall s a b . (a -> Maybe b) -> IntMap s a -> SomeIntMapWith (SupersetProof 'Int s) brefined-containers Data.IntMap.Strict.Refined Apply a function to all values in a map and collect only the Just results, returning a potentially smaller map.
mapMaybeWithKey :: (Key s -> a -> Maybe b) -> IntMap s a -> SomeIntMapWith (SupersetProof 'Int s) brefined-containers Data.IntMap.Strict.Refined Apply a function to all values in a map, together with their corresponding keys, and collect only the Just results, returning a potentially smaller map.
-
refined-containers Data.Map.Refined Apply a function to all values in a map and collect only the Just results, returning a potentially smaller map.
-
refined-containers Data.Map.Refined Apply a function to all values in a map, together with their corresponding keys, and collect only the Just results, returning a potentially smaller map.
-
refined-containers Data.Map.Strict.Refined Apply a function to all values in a map and collect only the Just results, returning a potentially smaller map.
-
refined-containers Data.Map.Strict.Refined Apply a function to all values in a map, together with their corresponding keys, and collect only the Just results, returning a potentially smaller map.
mapMaybe :: (a -> Maybe b) -> [a] -> [b]strict-base-types Data.Maybe.Strict Analogous to mapMaybe in Data.Maybe.
mapMaybe :: (a -> Maybe b) -> [a] -> [b]verset Verset The mapMaybe function is a version of map which can throw out elements. In particular, the functional argument returns something of type Maybe b. If this is Nothing, no element is added on to the result list. If it is Just b, then b is included in the result list.
Examples
Using mapMaybe f x is a shortcut for catMaybes $ map f x in most cases:>>> import GHC.Internal.Text.Read ( readMaybe ) >>> let readMaybeInt = readMaybe :: String -> Maybe Int >>> mapMaybe readMaybeInt ["1", "Foo", "3"] [1,3] >>> catMaybes $ map readMaybeInt ["1", "Foo", "3"] [1,3]
If we map the Just constructor, the entire list should be returned:>>> mapMaybe Just [1,2,3] [1,2,3]
data
MapMSym0 (a1 :: TyFun a ~> m b t a ~> m t b)singletons-base Control.Monad.Singletons No documentation available.
data
MapMSym1 (a6989586621680752083 :: a ~> m b) (b1 :: TyFun t a m t b)singletons-base Control.Monad.Singletons No documentation available.