Hoogle Search

Within LTS Haskell 24.26 (ghc-9.10.3)

Note that Stackage only displays results for the latest LTS and Nightly snapshot. Learn more.

Exact lookup

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

   errors	Control.Error

   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]
   

2. mapMaybeT :: (m (Maybe a) -> n (Maybe b)) -> MaybeT m a -> MaybeT n b

   errors	Control.Error

   Transform the computation inside a MaybeT.

   • runMaybeT (mapMaybeT f m) = f (runMaybeT
     m)

3. mapM_ :: HashTable h => ((k, v) -> ST s b) -> h s k v -> ST s ()

   hashtables	Data.HashTable.Class

   A side-effecting map over the key-value records of a hash table. O(n).

4. mapM_ :: HashTable h => ((k, v) -> IO a) -> IOHashTable h k v -> IO ()

   hashtables	Data.HashTable.IO

   See the documentation for this function in mapM_.

5. mapM_ :: ((k, v) -> ST s b) -> HashTable s k v -> ST s ()

   hashtables	Data.HashTable.ST.Basic

   See the documentation for this function in mapM_.

6. mapM_ :: ((k, v) -> ST s a) -> HashTable s k v -> ST s ()

   hashtables	Data.HashTable.ST.Cuckoo

   See the documentation for this function in mapM_.

7. mapM_ :: ((k, v) -> ST s b) -> HashTable s k v -> ST s ()

   hashtables	Data.HashTable.ST.Linear

   See the documentation for this function in Data.HashTable.Class#v:mapM_.

8. mapInputT :: (forall b . () => m b -> m b) -> InputT m a -> InputT m a

   haskeline	System.Console.Haskeline

   Map a user interaction by modifying the base monad computation.

9. map_ :: Term arg result => arg -> result

   lucid	Lucid.Html5

   map element

10. mapAccumL :: (Storable a, Storable b) => (acc -> a -> (acc, b)) -> acc -> Vector a -> (acc, Vector b)

    storablevector	Data.StorableVector

    The mapAccumL function behaves like a combination of map and foldl; it applies a function to each element of a Vector, passing an accumulating parameter from left to right, and returning a final value of this accumulator together with the new list.

Page 129 of many | Previous | Next