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mappend :: Monoid a => a -> a -> adimensional Numeric.Units.Dimensional.Prelude 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.
mapAndUnzipM :: Applicative m => (a -> m (b, c)) -> [a] -> m ([b], [c])distribution-opensuse OpenSuse.Prelude The mapAndUnzipM function maps its first argument over a list, returning the result as a pair of lists. This function is mainly used with complicated data structures or a state monad.
mapM :: (Traversable t, Monad m) => (a -> m b) -> t a -> m (t b)distribution-opensuse OpenSuse.Prelude Map each element of a structure to a monadic action, evaluate these actions from left to right, and collect the results. For a version that ignores the results see mapM_.
Examples
mapM is literally a traverse with a type signature restricted to Monad. Its implementation may be more efficient due to additional power of Monad.mapM :: (Traversable t, Monad m) => (a -> m b) -> t a -> m (t b)distribution-opensuse OpenSuse.Prelude Map each element of a structure to a monadic action, evaluate these actions from left to right, and collect the results. For a version that ignores the results see mapM_.
Examples
mapM is literally a traverse with a type signature restricted to Monad. Its implementation may be more efficient due to additional power of Monad.mapM_ :: (Foldable t, Monad m) => (a -> m b) -> t a -> m ()distribution-opensuse OpenSuse.Prelude Map each element of a structure to a monadic action, evaluate these actions from left to right, and ignore the results. For a version that doesn't ignore the results see mapM. mapM_ is just like traverse_, but specialised to monadic actions.
mapM_ :: (Foldable t, Monad m) => (a -> m b) -> t a -> m ()distribution-opensuse OpenSuse.Prelude Map each element of a structure to a monadic action, evaluate these actions from left to right, and ignore the results. For a version that doesn't ignore the results see mapM. mapM_ is just like traverse_, but specialised to monadic actions.
mapMaybeM :: Monad m => (a -> m (Maybe b)) -> [a] -> m [b]distribution-opensuse OpenSuse.Prelude A version of mapMaybe that works with a monadic predicate.
mappend :: Monoid a => a -> a -> adistribution-opensuse OpenSuse.Prelude 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.
mappend :: Monoid a => a -> a -> adistribution-opensuse OpenSuse.Prelude 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.
mapExcept :: (Either e a -> Either e' b) -> Except e a -> Except e' bdunai Control.Monad.Trans.MSF.Except Map the unwrapped computation using the given function.