Hoogle Search
Within LTS Haskell 24.6 (ghc-9.10.2)
Note that Stackage only displays results for the latest LTS and Nightly snapshot. Learn more.
mapRight :: (b -> c) -> Either a b -> Either a cextra Extra The mapRight function takes a function and applies it to an Either value iff the value takes the form Right _.
mapRight show (Left 1) == Left 1 mapRight show (Right True) == Right "True"
mappend :: Monoid a => a -> a -> abase-compat Data.Monoid.Compat An associative operation NOTE: This method is redundant and has the default implementation mappend = (<>) since base-4.11.0.0. Should it be implemented manually, since mappend is a synonym for (<>), it is expected that the two functions are defined the same way. In a future GHC release mappend will be removed from Monoid.
mapAccumM :: (Monad m, Traversable t) => (s -> a -> m (s, b)) -> s -> t a -> m (s, t b)base-compat Data.Traversable.Compat The mapAccumM function behaves like a combination of mapM and mapAccumL that traverses the structure while evaluating the actions and passing an accumulating parameter from left to right. It returns a final value of this accumulator together with the new structure. The accumulator is often used for caching the intermediate results of a computation.
Examples
Basic usage:>>> let expensiveDouble a = putStrLn ("Doubling " <> show a) >> pure (2 * a) >>> :{ mapAccumM (\cache a -> case lookup a cache of Nothing -> expensiveDouble a >>= \double -> pure ((a, double):cache, double) Just double -> pure (cache, double) ) [] [1, 2, 3, 1, 2, 3] :} Doubling 1 Doubling 2 Doubling 3 ([(3,6),(2,4),(1,2)],[2,4,6,2,4,6])mapPair :: Applicative f => (a -> f c, b -> f d) -> (a, b) -> f (c, d)utility-ht Control.Applicative.HT No documentation available.
mapTriple :: Applicative m => (a -> m d, b -> m e, c -> m f) -> (a, b, c) -> m (d, e, f)utility-ht Control.Applicative.HT No documentation available.
mapFst :: Functor f => (a -> f c) -> (a, b) -> f (c, b)utility-ht Control.Functor.HT No documentation available.
mapFst3 :: Functor f => (a -> f d) -> (a, b, c) -> f (d, b, c)utility-ht Control.Functor.HT No documentation available.
mapSnd :: Functor f => (b -> f c) -> (a, b) -> f (a, c)utility-ht Control.Functor.HT No documentation available.
mapSnd3 :: Functor f => (b -> f d) -> (a, b, c) -> f (a, d, c)utility-ht Control.Functor.HT No documentation available.
mapThd3 :: Functor f => (c -> f d) -> (a, b, c) -> f (a, b, d)utility-ht Control.Functor.HT No documentation available.