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Within LTS Haskell 24.64 (ghc-9.10.3)

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  1. mapM_ :: Monad m => (a -> m ()) -> FoldM m a ()

    foldl Control.Foldl

    Converts an effectful function to a fold. Specialized version of sink.

  2. mapMaybe :: Ord key => key -> T (Map key elem) (Maybe elem)

    data-accessor Data.Accessor.Container

    Treats a finite map like an infinite map, where all undefined elements are Nothing and defined elements are Just.

  3. mapMatrixWithIndex :: (Element a, Storable b) => ((Int, Int) -> a -> b) -> Matrix a -> Matrix b

    hmatrix Numeric.LinearAlgebra.Devel 

    >>> mapMatrixWithIndex (\(i,j) v -> 100*v + 10*fromIntegral i + fromIntegral j) (ident 3:: Matrix Double)
(3><3)
[ 100.0,   1.0,   2.0
,  10.0, 111.0,  12.0
,  20.0,  21.0, 122.0 ]

  4. mapMatrixWithIndexM :: (Element a, Storable b, Monad m) => ((Int, Int) -> a -> m b) -> Matrix a -> m (Matrix b)

    hmatrix Numeric.LinearAlgebra.Devel 

    >>> mapMatrixWithIndexM (\(i,j) v -> Just $ 100*v + 10*fromIntegral i + fromIntegral j) (ident 3:: Matrix Double)
Just (3><3)
[ 100.0,   1.0,   2.0
,  10.0, 111.0,  12.0
,  20.0,  21.0, 122.0 ]

  5. mapMatrixWithIndexM_ :: (Element a, Num a, Monad m) => ((Int, Int) -> a -> m ()) -> Matrix a -> m ()

    hmatrix Numeric.LinearAlgebra.Devel 

    >>> mapMatrixWithIndexM_ (\(i,j) v -> printf "m[%d,%d] = %.f\n" i j v :: IO()) ((2><3)[1 :: Double ..])
m[0,0] = 1
m[0,1] = 2
m[0,2] = 3
m[1,0] = 4
m[1,1] = 5
m[1,2] = 6

  6. mapM_ :: (a -> IO b) -> InputStream a -> IO (InputStream a)

    io-streams System.IO.Streams.Combinators

    Maps a side effect over an InputStream. mapM_ f s produces a new input stream that passes all output from s through the side-effecting IO action f. Example: 

    ghci> Streams.fromList [1,2,3] >>=
Streams.mapM_ (putStrLn . show . (*2)) >>=
Streams.toList
2
4
6
[1,2,3]

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

    strict Data.Strict.Maybe

    Analogous to mapMaybe in Data.Maybe.

  9. mapM_ :: (MonoFoldable mono, Applicative m) => (Element mono -> m ()) -> mono -> m ()

    mono-traversable Data.MonoTraversable.Unprefixed

    Synonym for omapM_

  10. mapMaybe :: (v1 -> Maybe v2) -> HashMap k v1 -> HashMap k v2

    rio RIO.HashMap

    Transform this map by applying a function to every value and retaining only some of them.

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