Safe Haskell	None
Language	Haskell2010

Prologue.Control.Monad

Synopsis

return :: Applicative m => a -> m a
(<<) :: Monad m => m a -> m b -> m a
(>>$) :: Monad m => m a -> m b -> m b
(>>=>) :: Monad m => (t1 -> t2 -> m a) -> (a -> m b) -> t1 -> t2 -> m b
(>>>=>) :: Monad m => (t1 -> t2 -> t3 -> m a) -> (a -> m b) -> t1 -> t2 -> t3 -> m b
(>>>>=>) :: Monad m => (t1 -> t2 -> t3 -> t4 -> m a) -> (a -> m b) -> t1 -> t2 -> t3 -> t4 -> m b
(<=<<) :: Monad m => (a -> m b) -> (t1 -> t2 -> m a) -> t1 -> t2 -> m b
(<=<<<) :: Monad m => (a -> m b) -> (t1 -> t2 -> t3 -> m a) -> t1 -> t2 -> t3 -> m b
(<=<<<<) :: Monad m => (a -> m b) -> (t1 -> t2 -> t3 -> t4 -> m a) -> t1 -> t2 -> t3 -> t4 -> m b
(>>~) :: Monad m => m a -> (a -> m b) -> m a
(=<<&) :: MonadFix m => (a -> m b) -> m a -> m a
void :: m a -> m ()
when :: (Applicative m, Mempty a) => Bool -> m a -> m a
unless :: (Applicative m, Mempty a) => Bool -> m a -> m a
when_ :: Applicative m => Bool -> m a -> m ()
unless_ :: Applicative m => Bool -> m a -> m ()
whenM :: (Monad m, Mempty a) => m Bool -> m a -> m a
unlessM :: (Monad m, Mempty a) => m Bool -> m a -> m a
whenM_ :: Monad m => m Bool -> m a -> m ()
unlessM_ :: Monad m => m Bool -> m a -> m ()
guard :: (MonadPlus m, ToBool' cond) => cond -> m ()
bind :: Monad m => (t1 -> m a) -> m t1 -> m a
bind2 :: Monad m => (t1 -> t2 -> m a) -> m t1 -> m t2 -> m a
bind3 :: Monad m => (t1 -> t2 -> t3 -> m a) -> m t1 -> m t2 -> m t3 -> m a
bind4 :: Monad m => (t1 -> t2 -> t3 -> t4 -> m a) -> m t1 -> m t2 -> m t3 -> m t4 -> m a
bind5 :: Monad m => (t1 -> t2 -> t3 -> t4 -> t5 -> m a) -> m t1 -> m t2 -> m t3 -> m t4 -> m t5 -> m a
join :: Monad m => m (m a) -> m a
class Applicative m => Monad (m :: * -> *) where
class (Alternative m, Monad m) => MonadPlus (m :: * -> *) where
replicateM :: Applicative m => Int -> m a -> m [a]
foldM_ :: (Foldable t, Monad m) => (b -> a -> m b) -> b -> t a -> m ()
foldM :: (Foldable t, Monad m) => (b -> a -> m b) -> b -> t a -> m b
zipWithM_ :: Applicative m => (a -> b -> m c) -> [a] -> [b] -> m ()
zipWithM :: Applicative m => (a -> b -> m c) -> [a] -> [b] -> m [c]
forever :: Applicative f => f a -> f b
(<=<) :: Monad m => (b -> m c) -> (a -> m b) -> a -> m c
(>=>) :: Monad m => (a -> m b) -> (b -> m c) -> a -> m c
(=<<) :: Monad m => (a -> m b) -> m a -> m b

Documentation

return :: Applicative m => a -> m a Source #

Deprecated: Use pure instead

(<<) :: Monad m => m a -> m b -> m a infixr 1 Source #

(>>$) :: Monad m => m a -> m b -> m b infixr 0 Source #

(>>=>) :: Monad m => (t1 -> t2 -> m a) -> (a -> m b) -> t1 -> t2 -> m b infixr 1 Source #

(>>>=>) :: Monad m => (t1 -> t2 -> t3 -> m a) -> (a -> m b) -> t1 -> t2 -> t3 -> m b infixr 1 Source #

(>>>>=>) :: Monad m => (t1 -> t2 -> t3 -> t4 -> m a) -> (a -> m b) -> t1 -> t2 -> t3 -> t4 -> m b infixr 1 Source #

(<=<<) :: Monad m => (a -> m b) -> (t1 -> t2 -> m a) -> t1 -> t2 -> m b infixr 1 Source #

(<=<<<) :: Monad m => (a -> m b) -> (t1 -> t2 -> t3 -> m a) -> t1 -> t2 -> t3 -> m b infixr 1 Source #

(<=<<<<) :: Monad m => (a -> m b) -> (t1 -> t2 -> t3 -> t4 -> m a) -> t1 -> t2 -> t3 -> t4 -> m b infixr 1 Source #

(>>~) :: Monad m => m a -> (a -> m b) -> m a Source #

(=<<&) :: MonadFix m => (a -> m b) -> m a -> m a infixr 1 Source #

void :: m a -> m () Source #

when :: (Applicative m, Mempty a) => Bool -> m a -> m a Source #

unless :: (Applicative m, Mempty a) => Bool -> m a -> m a Source #

when_ :: Applicative m => Bool -> m a -> m () Source #

unless_ :: Applicative m => Bool -> m a -> m () Source #

whenM :: (Monad m, Mempty a) => m Bool -> m a -> m a Source #

unlessM :: (Monad m, Mempty a) => m Bool -> m a -> m a Source #

whenM_ :: Monad m => m Bool -> m a -> m () Source #

unlessM_ :: Monad m => m Bool -> m a -> m () Source #

guard :: (MonadPlus m, ToBool' cond) => cond -> m () Source #

bind :: Monad m => (t1 -> m a) -> m t1 -> m a Source #

bind2 :: Monad m => (t1 -> t2 -> m a) -> m t1 -> m t2 -> m a Source #

bind3 :: Monad m => (t1 -> t2 -> t3 -> m a) -> m t1 -> m t2 -> m t3 -> m a Source #

bind4 :: Monad m => (t1 -> t2 -> t3 -> t4 -> m a) -> m t1 -> m t2 -> m t3 -> m t4 -> m a Source #

bind5 :: Monad m => (t1 -> t2 -> t3 -> t4 -> t5 -> m a) -> m t1 -> m t2 -> m t3 -> m t4 -> m t5 -> m a Source #

join :: Monad m => m (m a) -> m a #

The join function is the conventional monad join operator. It is used to remove one level of monadic structure, projecting its bound argument into the outer level.

class Applicative m => Monad (m :: * -> *) where #

The Monad class defines the basic operations over a monad, a concept from a branch of mathematics known as category theory. From the perspective of a Haskell programmer, however, it is best to think of a monad as an abstract datatype of actions. Haskell's do expressions provide a convenient syntax for writing monadic expressions.

Instances of Monad should satisfy the following laws:

```
return a >>= k  =  k a
```
```
m >>= return  =  m
```

m >>= (\x -> k x >>= h)  =  (m >>= k) >>= h

Furthermore, the Monad and Applicative operations should relate as follows:

```
pure = return
```
```
(<*>) = ap
```

The above laws imply:

```
fmap f xs  =  xs >>= return . f
```
```
(>>) = (*>)
```

and that pure and (<*>) satisfy the applicative functor laws.

The instances of Monad for lists, Maybe and IO defined in the Prelude satisfy these laws.

Minimal complete definition

(>>=)

Methods

(>>=) :: m a -> (a -> m b) -> m b infixl 1 #

Sequentially compose two actions, passing any value produced by the first as an argument to the second.

(>>) :: m a -> m b -> m b infixl 1 #

Sequentially compose two actions, discarding any value produced by the first, like sequencing operators (such as the semicolon) in imperative languages.

Instances

Monad []	Since: base-2.1
Instance details Defined in GHC.Base Methods (>>=) :: [a] -> (a -> [b]) -> [b] # (>>) :: [a] -> [b] -> [b] # return :: a -> [a] # fail :: String -> [a] #
Monad Maybe	Since: base-2.1
Instance details Defined in GHC.Base Methods (>>=) :: Maybe a -> (a -> Maybe b) -> Maybe b # (>>) :: Maybe a -> Maybe b -> Maybe b # return :: a -> Maybe a # fail :: String -> Maybe a #
Monad IO	Since: base-2.1
Instance details Defined in GHC.Base Methods (>>=) :: IO a -> (a -> IO b) -> IO b # (>>) :: IO a -> IO b -> IO b # return :: a -> IO a # fail :: String -> IO a #
Monad Par1	Since: base-4.9.0.0
Instance details Defined in GHC.Generics Methods (>>=) :: Par1 a -> (a -> Par1 b) -> Par1 b # (>>) :: Par1 a -> Par1 b -> Par1 b # return :: a -> Par1 a # fail :: String -> Par1 a #
Monad Q
Instance details Defined in Language.Haskell.TH.Syntax Methods (>>=) :: Q a -> (a -> Q b) -> Q b # (>>) :: Q a -> Q b -> Q b # return :: a -> Q a # fail :: String -> Q a #
Monad Complex	Since: base-4.9.0.0
Instance details Defined in Data.Complex Methods (>>=) :: Complex a -> (a -> Complex b) -> Complex b # (>>) :: Complex a -> Complex b -> Complex b # return :: a -> Complex a # fail :: String -> Complex a #
Monad Min	Since: base-4.9.0.0
Instance details Defined in Data.Semigroup Methods (>>=) :: Min a -> (a -> Min b) -> Min b # (>>) :: Min a -> Min b -> Min b # return :: a -> Min a # fail :: String -> Min a #
Monad Max	Since: base-4.9.0.0
Instance details Defined in Data.Semigroup Methods (>>=) :: Max a -> (a -> Max b) -> Max b # (>>) :: Max a -> Max b -> Max b # return :: a -> Max a # fail :: String -> Max a #
Monad First	Since: base-4.9.0.0
Instance details Defined in Data.Semigroup Methods (>>=) :: First a -> (a -> First b) -> First b # (>>) :: First a -> First b -> First b # return :: a -> First a # fail :: String -> First a #
Monad Last	Since: base-4.9.0.0
Instance details Defined in Data.Semigroup Methods (>>=) :: Last a -> (a -> Last b) -> Last b # (>>) :: Last a -> Last b -> Last b # return :: a -> Last a # fail :: String -> Last a #
Monad Option	Since: base-4.9.0.0
Instance details Defined in Data.Semigroup Methods (>>=) :: Option a -> (a -> Option b) -> Option b # (>>) :: Option a -> Option b -> Option b # return :: a -> Option a # fail :: String -> Option a #
Monad Identity	Since: base-4.8.0.0
Instance details Defined in Data.Functor.Identity Methods (>>=) :: Identity a -> (a -> Identity b) -> Identity b # (>>) :: Identity a -> Identity b -> Identity b # return :: a -> Identity a # fail :: String -> Identity a #
Monad STM	Since: base-4.3.0.0
Instance details Defined in GHC.Conc.Sync Methods (>>=) :: STM a -> (a -> STM b) -> STM b # (>>) :: STM a -> STM b -> STM b # return :: a -> STM a # fail :: String -> STM a #
Monad First
Instance details Defined in Data.Monoid Methods (>>=) :: First a -> (a -> First b) -> First b # (>>) :: First a -> First b -> First b # return :: a -> First a # fail :: String -> First a #
Monad Last
Instance details Defined in Data.Monoid Methods (>>=) :: Last a -> (a -> Last b) -> Last b # (>>) :: Last a -> Last b -> Last b # return :: a -> Last a # fail :: String -> Last a #
Monad Dual	Since: base-4.8.0.0
Instance details Defined in Data.Semigroup.Internal Methods (>>=) :: Dual a -> (a -> Dual b) -> Dual b # (>>) :: Dual a -> Dual b -> Dual b # return :: a -> Dual a # fail :: String -> Dual a #
Monad Sum	Since: base-4.8.0.0
Instance details Defined in Data.Semigroup.Internal Methods (>>=) :: Sum a -> (a -> Sum b) -> Sum b # (>>) :: Sum a -> Sum b -> Sum b # return :: a -> Sum a # fail :: String -> Sum a #
Monad Product	Since: base-4.8.0.0
Instance details Defined in Data.Semigroup.Internal Methods (>>=) :: Product a -> (a -> Product b) -> Product b # (>>) :: Product a -> Product b -> Product b # return :: a -> Product a # fail :: String -> Product a #
Monad Down	Since: base-4.11.0.0
Instance details Defined in Data.Ord Methods (>>=) :: Down a -> (a -> Down b) -> Down b # (>>) :: Down a -> Down b -> Down b # return :: a -> Down a # fail :: String -> Down a #
Monad ReadPrec	Since: base-2.1
Instance details Defined in Text.ParserCombinators.ReadPrec Methods (>>=) :: ReadPrec a -> (a -> ReadPrec b) -> ReadPrec b # (>>) :: ReadPrec a -> ReadPrec b -> ReadPrec b # return :: a -> ReadPrec a # fail :: String -> ReadPrec a #
Monad ReadP	Since: base-2.1
Instance details Defined in Text.ParserCombinators.ReadP Methods (>>=) :: ReadP a -> (a -> ReadP b) -> ReadP b # (>>) :: ReadP a -> ReadP b -> ReadP b # return :: a -> ReadP a # fail :: String -> ReadP a #
Monad NonEmpty	Since: base-4.9.0.0
Instance details Defined in GHC.Base Methods (>>=) :: NonEmpty a -> (a -> NonEmpty b) -> NonEmpty b # (>>) :: NonEmpty a -> NonEmpty b -> NonEmpty b # return :: a -> NonEmpty a # fail :: String -> NonEmpty a #
Monad Put
Instance details Defined in Data.ByteString.Builder.Internal Methods (>>=) :: Put a -> (a -> Put b) -> Put b # (>>) :: Put a -> Put b -> Put b # return :: a -> Put a # fail :: String -> Put a #
Monad Tree
Instance details Defined in Data.Tree Methods (>>=) :: Tree a -> (a -> Tree b) -> Tree b # (>>) :: Tree a -> Tree b -> Tree b # return :: a -> Tree a # fail :: String -> Tree a #
Monad Seq
Instance details Defined in Data.Sequence.Internal Methods (>>=) :: Seq a -> (a -> Seq b) -> Seq b # (>>) :: Seq a -> Seq b -> Seq b # return :: a -> Seq a # fail :: String -> Seq a #
Monad DList
Instance details Defined in Data.DList Methods (>>=) :: DList a -> (a -> DList b) -> DList b # (>>) :: DList a -> DList b -> DList b # return :: a -> DList a # fail :: String -> DList a #
Monad Vector
Instance details Defined in Data.Vector Methods (>>=) :: Vector a -> (a -> Vector b) -> Vector b # (>>) :: Vector a -> Vector b -> Vector b # return :: a -> Vector a # fail :: String -> Vector a #
Monad SmallArray
Instance details Defined in Data.Primitive.SmallArray Methods (>>=) :: SmallArray a -> (a -> SmallArray b) -> SmallArray b # (>>) :: SmallArray a -> SmallArray b -> SmallArray b # return :: a -> SmallArray a # fail :: String -> SmallArray a #
Monad Array
Instance details Defined in Data.Primitive.Array Methods (>>=) :: Array a -> (a -> Array b) -> Array b # (>>) :: Array a -> Array b -> Array b # return :: a -> Array a # fail :: String -> Array a #
Monad P	Since: base-2.1
Instance details Defined in Text.ParserCombinators.ReadP Methods (>>=) :: P a -> (a -> P b) -> P b # (>>) :: P a -> P b -> P b # return :: a -> P a # fail :: String -> P a #
Monad OneTuple #
Instance details Defined in Prologue.Data.OneTuple Methods (>>=) :: OneTuple a -> (a -> OneTuple b) -> OneTuple b # (>>) :: OneTuple a -> OneTuple b -> OneTuple b # return :: a -> OneTuple a # fail :: String -> OneTuple a #
Monad (Either e)	Since: base-4.4.0.0
Instance details Defined in Data.Either Methods (>>=) :: Either e a -> (a -> Either e b) -> Either e b # (>>) :: Either e a -> Either e b -> Either e b # return :: a -> Either e a # fail :: String -> Either e a #
Monad (U1 :: * -> *)	Since: base-4.9.0.0
Instance details Defined in GHC.Generics Methods (>>=) :: U1 a -> (a -> U1 b) -> U1 b # (>>) :: U1 a -> U1 b -> U1 b # return :: a -> U1 a # fail :: String -> U1 a #
Monoid a => Monad ((,) a)	Since: base-4.9.0.0
Instance details Defined in GHC.Base Methods (>>=) :: (a, a0) -> (a0 -> (a, b)) -> (a, b) # (>>) :: (a, a0) -> (a, b) -> (a, b) # return :: a0 -> (a, a0) # fail :: String -> (a, a0) #
Representable f => Monad (Co f)
Instance details Defined in Data.Functor.Rep Methods (>>=) :: Co f a -> (a -> Co f b) -> Co f b # (>>) :: Co f a -> Co f b -> Co f b # return :: a -> Co f a # fail :: String -> Co f a #
Monad m => Monad (WrappedMonad m)
Instance details Defined in Control.Applicative Methods (>>=) :: WrappedMonad m a -> (a -> WrappedMonad m b) -> WrappedMonad m b # (>>) :: WrappedMonad m a -> WrappedMonad m b -> WrappedMonad m b # return :: a -> WrappedMonad m a # fail :: String -> WrappedMonad m a #
Monad (Proxy :: * -> *)	Since: base-4.7.0.0
Instance details Defined in Data.Proxy Methods (>>=) :: Proxy a -> (a -> Proxy b) -> Proxy b # (>>) :: Proxy a -> Proxy b -> Proxy b # return :: a -> Proxy a # fail :: String -> Proxy a #
Monad m => Monad (MaybeT m)
Instance details Defined in Control.Monad.Trans.Maybe Methods (>>=) :: MaybeT m a -> (a -> MaybeT m b) -> MaybeT m b # (>>) :: MaybeT m a -> MaybeT m b -> MaybeT m b # return :: a -> MaybeT m a # fail :: String -> MaybeT m a #
Alternative f => Monad (Cofree f)
Instance details Defined in Control.Comonad.Cofree Methods (>>=) :: Cofree f a -> (a -> Cofree f b) -> Cofree f b # (>>) :: Cofree f a -> Cofree f b -> Cofree f b # return :: a -> Cofree f a # fail :: String -> Cofree f a #
Functor f => Monad (Free f)
Instance details Defined in Control.Monad.Free Methods (>>=) :: Free f a -> (a -> Free f b) -> Free f b # (>>) :: Free f a -> Free f b -> Free f b # return :: a -> Free f a # fail :: String -> Free f a #
Monad (ImpossibleM1 :: * -> *)
Instance details Defined in Data.Impossible Methods (>>=) :: ImpossibleM1 a -> (a -> ImpossibleM1 b) -> ImpossibleM1 b # (>>) :: ImpossibleM1 a -> ImpossibleM1 b -> ImpossibleM1 b # return :: a -> ImpossibleM1 a # fail :: String -> ImpossibleM1 a #
Monad m => Monad (Yoneda m)
Instance details Defined in Data.Functor.Yoneda Methods (>>=) :: Yoneda m a -> (a -> Yoneda m b) -> Yoneda m b # (>>) :: Yoneda m a -> Yoneda m b -> Yoneda m b # return :: a -> Yoneda m a # fail :: String -> Yoneda m a #
Monad (ReifiedGetter s)
Instance details Defined in Control.Lens.Reified Methods (>>=) :: ReifiedGetter s a -> (a -> ReifiedGetter s b) -> ReifiedGetter s b # (>>) :: ReifiedGetter s a -> ReifiedGetter s b -> ReifiedGetter s b # return :: a -> ReifiedGetter s a # fail :: String -> ReifiedGetter s a #
Monad (ReifiedFold s)
Instance details Defined in Control.Lens.Reified Methods (>>=) :: ReifiedFold s a -> (a -> ReifiedFold s b) -> ReifiedFold s b # (>>) :: ReifiedFold s a -> ReifiedFold s b -> ReifiedFold s b # return :: a -> ReifiedFold s a # fail :: String -> ReifiedFold s a #
(Monad (Rep p), Representable p) => Monad (Prep p)
Instance details Defined in Data.Profunctor.Rep Methods (>>=) :: Prep p a -> (a -> Prep p b) -> Prep p b # (>>) :: Prep p a -> Prep p b -> Prep p b # return :: a -> Prep p a # fail :: String -> Prep p a #
Monad f => Monad (Rec1 f)	Since: base-4.9.0.0
Instance details Defined in GHC.Generics Methods (>>=) :: Rec1 f a -> (a -> Rec1 f b) -> Rec1 f b # (>>) :: Rec1 f a -> Rec1 f b -> Rec1 f b # return :: a -> Rec1 f a # fail :: String -> Rec1 f a #
Monad f => Monad (Alt f)
Instance details Defined in Data.Semigroup.Internal Methods (>>=) :: Alt f a -> (a -> Alt f b) -> Alt f b # (>>) :: Alt f a -> Alt f b -> Alt f b # return :: a -> Alt f a # fail :: String -> Alt f a #
Monad m => Monad (IdentityT m)
Instance details Defined in Control.Monad.Trans.Identity Methods (>>=) :: IdentityT m a -> (a -> IdentityT m b) -> IdentityT m b # (>>) :: IdentityT m a -> IdentityT m b -> IdentityT m b # return :: a -> IdentityT m a # fail :: String -> IdentityT m a #
(Applicative f, Monad f) => Monad (WhenMissing f x)	Equivalent to `ReaderT k (ReaderT x (MaybeT f))`. Since: containers-0.5.9
Instance details Defined in Data.IntMap.Internal Methods (>>=) :: WhenMissing f x a -> (a -> WhenMissing f x b) -> WhenMissing f x b # (>>) :: WhenMissing f x a -> WhenMissing f x b -> WhenMissing f x b # return :: a -> WhenMissing f x a # fail :: String -> WhenMissing f x a #
Monad m => Monad (ExceptT e m)
Instance details Defined in Control.Monad.Trans.Except Methods (>>=) :: ExceptT e m a -> (a -> ExceptT e m b) -> ExceptT e m b # (>>) :: ExceptT e m a -> ExceptT e m b -> ExceptT e m b # return :: a -> ExceptT e m a # fail :: String -> ExceptT e m a #
(Functor f, Monad m) => Monad (FreeT f m)
Instance details Defined in Control.Monad.Trans.Free Methods (>>=) :: FreeT f m a -> (a -> FreeT f m b) -> FreeT f m b # (>>) :: FreeT f m a -> FreeT f m b -> FreeT f m b # return :: a -> FreeT f m a # fail :: String -> FreeT f m a #
(Alternative f, Monad w) => Monad (CofreeT f w)
Instance details Defined in Control.Comonad.Trans.Cofree Methods (>>=) :: CofreeT f w a -> (a -> CofreeT f w b) -> CofreeT f w b # (>>) :: CofreeT f w a -> CofreeT f w b -> CofreeT f w b # return :: a -> CofreeT f w a # fail :: String -> CofreeT f w a #
(Monad m, Error e) => Monad (ErrorT e m)
Instance details Defined in Control.Monad.Trans.Error Methods (>>=) :: ErrorT e m a -> (a -> ErrorT e m b) -> ErrorT e m b # (>>) :: ErrorT e m a -> ErrorT e m b -> ErrorT e m b # return :: a -> ErrorT e m a # fail :: String -> ErrorT e m a #
Monad (Indexed i a)
Instance details Defined in Control.Lens.Internal.Indexed Methods (>>=) :: Indexed i a a0 -> (a0 -> Indexed i a b) -> Indexed i a b # (>>) :: Indexed i a a0 -> Indexed i a b -> Indexed i a b # return :: a0 -> Indexed i a a0 # fail :: String -> Indexed i a a0 #
Monad (Tagged s)
Instance details Defined in Data.Tagged Methods (>>=) :: Tagged s a -> (a -> Tagged s b) -> Tagged s b # (>>) :: Tagged s a -> Tagged s b -> Tagged s b # return :: a -> Tagged s a # fail :: String -> Tagged s a #
Monad ((->) r :: * -> *)	Since: base-2.1
Instance details Defined in GHC.Base Methods (>>=) :: (r -> a) -> (a -> r -> b) -> r -> b # (>>) :: (r -> a) -> (r -> b) -> r -> b # return :: a -> r -> a # fail :: String -> r -> a #
(Monad f, Monad g) => Monad (f :*: g)	Since: base-4.9.0.0
Instance details Defined in GHC.Generics Methods (>>=) :: (f :: g) a -> (a -> (f :: g) b) -> (f :: g) b # (>>) :: (f :: g) a -> (f :: g) b -> (f :: g) b # return :: a -> (f :: g) a # fail :: String -> (f :: g) a #
(Monad f, Monad g) => Monad (Product f g)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Product Methods (>>=) :: Product f g a -> (a -> Product f g b) -> Product f g b # (>>) :: Product f g a -> Product f g b -> Product f g b # return :: a -> Product f g a # fail :: String -> Product f g a #
Monad (Cokleisli w a)
Instance details Defined in Control.Comonad Methods (>>=) :: Cokleisli w a a0 -> (a0 -> Cokleisli w a b) -> Cokleisli w a b # (>>) :: Cokleisli w a a0 -> Cokleisli w a b -> Cokleisli w a b # return :: a0 -> Cokleisli w a a0 # fail :: String -> Cokleisli w a a0 #
(Monad f, Applicative f) => Monad (WhenMatched f x y)	Equivalent to `ReaderT Key (ReaderT x (ReaderT y (MaybeT f)))` Since: containers-0.5.9
Instance details Defined in Data.IntMap.Internal Methods (>>=) :: WhenMatched f x y a -> (a -> WhenMatched f x y b) -> WhenMatched f x y b # (>>) :: WhenMatched f x y a -> WhenMatched f x y b -> WhenMatched f x y b # return :: a -> WhenMatched f x y a # fail :: String -> WhenMatched f x y a #
(Applicative f, Monad f) => Monad (WhenMissing f k x)	Equivalent to `ReaderT k (ReaderT x (MaybeT f))` . Since: containers-0.5.9
Instance details Defined in Data.Map.Internal Methods (>>=) :: WhenMissing f k x a -> (a -> WhenMissing f k x b) -> WhenMissing f k x b # (>>) :: WhenMissing f k x a -> WhenMissing f k x b -> WhenMissing f k x b # return :: a -> WhenMissing f k x a # fail :: String -> WhenMissing f k x a #
Monad f => Monad (M1 i c f)	Since: base-4.9.0.0
Instance details Defined in GHC.Generics Methods (>>=) :: M1 i c f a -> (a -> M1 i c f b) -> M1 i c f b # (>>) :: M1 i c f a -> M1 i c f b -> M1 i c f b # return :: a -> M1 i c f a # fail :: String -> M1 i c f a #
(Monad f, Applicative f) => Monad (WhenMatched f k x y)	Equivalent to `ReaderT k (ReaderT x (ReaderT y (MaybeT f)))` Since: containers-0.5.9
Instance details Defined in Data.Map.Internal Methods (>>=) :: WhenMatched f k x y a -> (a -> WhenMatched f k x y b) -> WhenMatched f k x y b # (>>) :: WhenMatched f k x y a -> WhenMatched f k x y b -> WhenMatched f k x y b # return :: a -> WhenMatched f k x y a # fail :: String -> WhenMatched f k x y a #

class (Alternative m, Monad m) => MonadPlus (m :: * -> *) where #

Monads that also support choice and failure.

Methods

mzero :: m a #

The identity of mplus. It should also satisfy the equations

mzero >>= f  =  mzero
v >> mzero   =  mzero

The default definition is

mzero = empty

mplus :: m a -> m a -> m a #

An associative operation. The default definition is

mplus = (<|>)

Instances

MonadPlus []	Since: base-2.1
Instance details Defined in GHC.Base Methods mzero :: [a] # mplus :: [a] -> [a] -> [a] #
MonadPlus Maybe	Since: base-2.1
Instance details Defined in GHC.Base Methods mzero :: Maybe a # mplus :: Maybe a -> Maybe a -> Maybe a #
MonadPlus IO	Since: base-4.9.0.0
Instance details Defined in GHC.Base Methods mzero :: IO a # mplus :: IO a -> IO a -> IO a #
MonadPlus Option	Since: base-4.9.0.0
Instance details Defined in Data.Semigroup Methods mzero :: Option a # mplus :: Option a -> Option a -> Option a #
MonadPlus STM	Since: base-4.3.0.0
Instance details Defined in GHC.Conc.Sync Methods mzero :: STM a # mplus :: STM a -> STM a -> STM a #
MonadPlus ReadPrec	Since: base-2.1
Instance details Defined in Text.ParserCombinators.ReadPrec Methods mzero :: ReadPrec a # mplus :: ReadPrec a -> ReadPrec a -> ReadPrec a #
MonadPlus ReadP	Since: base-2.1
Instance details Defined in Text.ParserCombinators.ReadP Methods mzero :: ReadP a # mplus :: ReadP a -> ReadP a -> ReadP a #
MonadPlus Seq
Instance details Defined in Data.Sequence.Internal Methods mzero :: Seq a # mplus :: Seq a -> Seq a -> Seq a #
MonadPlus DList
Instance details Defined in Data.DList Methods mzero :: DList a # mplus :: DList a -> DList a -> DList a #
MonadPlus Vector
Instance details Defined in Data.Vector Methods mzero :: Vector a # mplus :: Vector a -> Vector a -> Vector a #
MonadPlus SmallArray
Instance details Defined in Data.Primitive.SmallArray Methods mzero :: SmallArray a # mplus :: SmallArray a -> SmallArray a -> SmallArray a #
MonadPlus Array
Instance details Defined in Data.Primitive.Array Methods mzero :: Array a # mplus :: Array a -> Array a -> Array a #
MonadPlus P	Since: base-2.1
Instance details Defined in Text.ParserCombinators.ReadP Methods mzero :: P a # mplus :: P a -> P a -> P a #
MonadPlus (U1 :: * -> *)	Since: base-4.9.0.0
Instance details Defined in GHC.Generics Methods mzero :: U1 a # mplus :: U1 a -> U1 a -> U1 a #
MonadPlus (Proxy :: * -> *)	Since: base-4.9.0.0
Instance details Defined in Data.Proxy Methods mzero :: Proxy a # mplus :: Proxy a -> Proxy a -> Proxy a #
Monad m => MonadPlus (MaybeT m)
Instance details Defined in Control.Monad.Trans.Maybe Methods mzero :: MaybeT m a # mplus :: MaybeT m a -> MaybeT m a -> MaybeT m a #
(Functor v, MonadPlus v) => MonadPlus (Free v)	This violates the MonadPlus laws, handle with care.
Instance details Defined in Control.Monad.Free Methods mzero :: Free v a # mplus :: Free v a -> Free v a -> Free v a #
MonadPlus m => MonadPlus (Yoneda m)
Instance details Defined in Data.Functor.Yoneda Methods mzero :: Yoneda m a # mplus :: Yoneda m a -> Yoneda m a -> Yoneda m a #
MonadPlus (ReifiedFold s)
Instance details Defined in Control.Lens.Reified Methods mzero :: ReifiedFold s a # mplus :: ReifiedFold s a -> ReifiedFold s a -> ReifiedFold s a #
MonadPlus f => MonadPlus (Rec1 f)	Since: base-4.9.0.0
Instance details Defined in GHC.Generics Methods mzero :: Rec1 f a # mplus :: Rec1 f a -> Rec1 f a -> Rec1 f a #
MonadPlus f => MonadPlus (Alt f)
Instance details Defined in Data.Semigroup.Internal Methods mzero :: Alt f a # mplus :: Alt f a -> Alt f a -> Alt f a #
MonadPlus m => MonadPlus (IdentityT m)
Instance details Defined in Control.Monad.Trans.Identity Methods mzero :: IdentityT m a # mplus :: IdentityT m a -> IdentityT m a -> IdentityT m a #
(Monad m, Monoid e) => MonadPlus (ExceptT e m)
Instance details Defined in Control.Monad.Trans.Except Methods mzero :: ExceptT e m a # mplus :: ExceptT e m a -> ExceptT e m a -> ExceptT e m a #
(Functor f, MonadPlus m) => MonadPlus (FreeT f m)
Instance details Defined in Control.Monad.Trans.Free Methods mzero :: FreeT f m a # mplus :: FreeT f m a -> FreeT f m a -> FreeT f m a #
(Monad m, Error e) => MonadPlus (ErrorT e m)
Instance details Defined in Control.Monad.Trans.Error Methods mzero :: ErrorT e m a # mplus :: ErrorT e m a -> ErrorT e m a -> ErrorT e m a #
(MonadPlus f, MonadPlus g) => MonadPlus (f :*: g)	Since: base-4.9.0.0
Instance details Defined in GHC.Generics Methods mzero :: (f :: g) a # mplus :: (f :: g) a -> (f :: g) a -> (f :: g) a #
(MonadPlus f, MonadPlus g) => MonadPlus (Product f g)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Product Methods mzero :: Product f g a # mplus :: Product f g a -> Product f g a -> Product f g a #
MonadPlus f => MonadPlus (M1 i c f)	Since: base-4.9.0.0
Instance details Defined in GHC.Generics Methods mzero :: M1 i c f a # mplus :: M1 i c f a -> M1 i c f a -> M1 i c f a #

replicateM :: Applicative m => Int -> m a -> m [a] #

replicateM n act performs the action n times, gathering the results.

foldM_ :: (Foldable t, Monad m) => (b -> a -> m b) -> b -> t a -> m () #

Like foldM, but discards the result.

foldM :: (Foldable t, Monad m) => (b -> a -> m b) -> b -> t a -> m b #

The foldM function is analogous to foldl, except that its result is encapsulated in a monad. Note that foldM works from left-to-right over the list arguments. This could be an issue where (>>) and the `folded function' are not commutative.

foldM f a1 [x1, x2, ..., xm]

==

do
  a2 <- f a1 x1
  a3 <- f a2 x2
  ...
  f am xm

If right-to-left evaluation is required, the input list should be reversed.

Note: foldM is the same as foldlM

zipWithM_ :: Applicative m => (a -> b -> m c) -> [a] -> [b] -> m () #

zipWithM_ is the extension of zipWithM which ignores the final result.

zipWithM :: Applicative m => (a -> b -> m c) -> [a] -> [b] -> m [c] #

The zipWithM function generalizes zipWith to arbitrary applicative functors.

forever :: Applicative f => f a -> f b #

forever act repeats the action infinitely.

(<=<) :: Monad m => (b -> m c) -> (a -> m b) -> a -> m c infixr 1 #

Right-to-left Kleisli composition of monads. (>=>), with the arguments flipped.

Note how this operator resembles function composition (.):

(.)   ::            (b ->   c) -> (a ->   b) -> a ->   c
(<=<) :: Monad m => (b -> m c) -> (a -> m b) -> a -> m c

(>=>) :: Monad m => (a -> m b) -> (b -> m c) -> a -> m c infixr 1 #

Left-to-right Kleisli composition of monads.

(=<<) :: Monad m => (a -> m b) -> m a -> m b infixr 1 #

Same as >>=, but with the arguments interchanged.