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sequence_ :: (Foldable t, Monad m) => t (m a) -> m ()base Prelude Evaluate each monadic action in the structure from left to right, and ignore the results. For a version that doesn't ignore the results see sequence. sequence_ is just like sequenceA_, but specialised to monadic actions.
sequence_ :: (Foldable t, Monad m) => t (m a) -> m ()base Control.Monad Evaluate each monadic action in the structure from left to right, and ignore the results. For a version that doesn't ignore the results see sequence. sequence_ is just like sequenceA_, but specialised to monadic actions.
sequenceA_ :: (Foldable t, Applicative f) => t (f a) -> f ()base Data.Foldable Evaluate each action in the structure from left to right, and ignore the results. For a version that doesn't ignore the results see sequenceA. sequenceA_ is just like sequence_, but generalised to Applicative actions.
Examples
Basic usage:>>> sequenceA_ [print "Hello", print "world", print "!"] "Hello" "world" "!"
sequence_ :: (Foldable t, Monad m) => t (m a) -> m ()base Data.Foldable Evaluate each monadic action in the structure from left to right, and ignore the results. For a version that doesn't ignore the results see sequence. sequence_ is just like sequenceA_, but specialised to monadic actions.
sequenceA :: (Traversable t, Applicative f) => t (f a) -> f (t a)base Data.Traversable Evaluate each action in the structure from left to right, and collect the results. For a version that ignores the results see sequenceA_.
Examples
Basic usage: For the first two examples we show sequenceA fully evaluating a a structure and collecting the results.>>> sequenceA [Just 1, Just 2, Just 3] Just [1,2,3]
>>> sequenceA [Right 1, Right 2, Right 3] Right [1,2,3]
The next two example show Nothing and Just will short circuit the resulting structure if present in the input. For more context, check the Traversable instances for Either and Maybe.>>> sequenceA [Just 1, Just 2, Just 3, Nothing] Nothing
>>> sequenceA [Right 1, Right 2, Right 3, Left 4] Left 4
sequenceWithIOErrors_ :: [IO ()] -> IO ()directory System.Directory.Internal No documentation available.
sequenceQ :: Monad m => forall a . () => [m a] -> m [a]template-haskell Language.Haskell.TH.Syntax No documentation available.
sequence1Of_ :: Functor f => Getting (TraversedF a f) s (f a) -> s -> f ()lens Control.Lens.Combinators See sequenceAOf_ and traverse1Of_.
sequence1Of_ :: Apply f => Fold1 s (f a) -> s -> f ()
sequenceAOf :: LensLike f s t (f b) b -> s -> f tlens Control.Lens.Combinators Evaluate each action in the structure from left to right, and collect the results.
>>> sequenceAOf both ([1,2],[3,4]) [(1,3),(1,4),(2,3),(2,4)]
sequenceA ≡ sequenceAOf traverse ≡ traverse id sequenceAOf l ≡ traverseOf l id ≡ l id
sequenceAOf :: Functor f => Iso s t (f b) b -> s -> f t sequenceAOf :: Functor f => Lens s t (f b) b -> s -> f t sequenceAOf :: Applicative f => Traversal s t (f b) b -> s -> f t
sequenceAOf_ :: Functor f => Getting (Traversed a f) s (f a) -> s -> f ()lens Control.Lens.Combinators Evaluate each action in observed by a Fold on a structure from left to right, ignoring the results.
sequenceA_ ≡ sequenceAOf_ folded
>>> sequenceAOf_ both (putStrLn "hello",putStrLn "world") hello world
sequenceAOf_ :: Functor f => Getter s (f a) -> s -> f () sequenceAOf_ :: Applicative f => Fold s (f a) -> s -> f () sequenceAOf_ :: Functor f => Lens' s (f a) -> s -> f () sequenceAOf_ :: Functor f => Iso' s (f a) -> s -> f () sequenceAOf_ :: Applicative f => Traversal' s (f a) -> s -> f () sequenceAOf_ :: Applicative f => Prism' s (f a) -> s -> f ()