Monad.Plus

Documentation

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

Defined in GHC.Base

Methods

mzero :: [a]

mplus :: [a] -> [a] -> [a]

MonadPlus Maybe

Since: base-2.1

Defined in GHC.Base

Methods

mzero :: Maybe a

mplus :: Maybe a -> Maybe a -> Maybe a

MonadPlus IO

Since: base-4.9.0.0

Defined in GHC.Base

Methods

mzero :: IO a

mplus :: IO a -> IO a -> IO a

MonadPlus IResult

Defined in Data.Aeson.Types.Internal

Methods

mzero :: IResult a

mplus :: IResult a -> IResult a -> IResult a

MonadPlus Result

Defined in Data.Aeson.Types.Internal

Methods

mzero :: Result a

mplus :: Result a -> Result a -> Result a

MonadPlus Parser

Defined in Data.Aeson.Types.Internal

Methods

mzero :: Parser a

mplus :: Parser a -> Parser a -> Parser a

MonadPlus Option

Since: base-4.9.0.0

Defined in Data.Semigroup

Methods

mzero :: Option a

mplus :: Option a -> Option a -> Option a

MonadPlus STM

Since: base-4.3.0.0

Defined in GHC.Conc.Sync

Methods

mzero :: STM a

mplus :: STM a -> STM a -> STM a

MonadPlus ReadPrec

Since: base-2.1

Defined in Text.ParserCombinators.ReadPrec

Methods

mzero :: ReadPrec a

mplus :: ReadPrec a -> ReadPrec a -> ReadPrec a

MonadPlus ReadP

Since: base-2.1

Defined in Text.ParserCombinators.ReadP

Methods

mzero :: ReadP a

mplus :: ReadP a -> ReadP a -> ReadP a

MonadPlus Seq

Defined in Data.Sequence.Internal

Methods

mzero :: Seq a

mplus :: Seq a -> Seq a -> Seq a

MonadPlus DList

Defined in Data.DList

Methods

mzero :: DList a

mplus :: DList a -> DList a -> DList a

MonadPlus Vector

Defined in Data.Vector

Methods

mzero :: Vector a

mplus :: Vector a -> Vector a -> Vector a

MonadPlus ReadM

Defined in Options.Applicative.Types

Methods

mzero :: ReadM a

mplus :: ReadM a -> ReadM a -> ReadM a

MonadPlus SmallArray

Defined in Data.Primitive.SmallArray

Methods

mzero :: SmallArray a

mplus :: SmallArray a -> SmallArray a -> SmallArray a

MonadPlus Array

Defined in Data.Primitive.Array

Methods

mzero :: Array a

mplus :: Array a -> Array a -> Array a

MonadPlus Element

Defined in Control.Concurrent.Chan.Unagi.NoBlocking.Types

Methods

mzero :: Element a

mplus :: Element a -> Element a -> Element a

MonadPlus P

Since: base-2.1

Defined in Text.ParserCombinators.ReadP

Methods

mzero :: P a

mplus :: P a -> P a -> P a

() :=> (MonadPlus [])

Defined in Data.Constraint

Methods

ins :: () :- MonadPlus []

() :=> (MonadPlus Maybe)

Defined in Data.Constraint

Methods

ins :: () :- MonadPlus Maybe

MonadPlus (U1 :: * -> *)

Since: base-4.9.0.0

Defined in GHC.Generics

Methods

mzero :: U1 a

mplus :: U1 a -> U1 a -> U1 a

(ArrowApply a, ArrowPlus a) => MonadPlus (ArrowMonad a)

Since: base-4.6.0.0

Defined in Control.Arrow

Methods

mzero :: ArrowMonad a a0

mplus :: ArrowMonad a a0 -> ArrowMonad a a0 -> ArrowMonad a a0

MonadPlus (Proxy :: * -> *)

Since: base-4.9.0.0

Defined in Data.Proxy

Methods

mzero :: Proxy a

mplus :: Proxy a -> Proxy a -> Proxy a

Monad m => MonadPlus (MaybeT m)

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.

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)

Defined in Data.Functor.Yoneda

Methods

mzero :: Yoneda m a

mplus :: Yoneda m a -> Yoneda m a -> Yoneda m a

MonadPlus (ReifiedFold s)

Defined in Control.Lens.Reified

Methods

mzero :: ReifiedFold s a

mplus :: ReifiedFold s a -> ReifiedFold s a -> ReifiedFold s a

Monad m => MonadPlus (ListT m)

Defined in List.Transformer

Methods

mzero :: ListT m a

mplus :: ListT m a -> ListT m a -> ListT m a

MonadPlus (LogicT m)

Defined in Control.Monad.Logic

Methods

mzero :: LogicT m a

mplus :: LogicT m a -> LogicT m a -> LogicT m a

(MonadPlus m) :=> (Alternative (WrappedMonad m))

Defined in Data.Constraint

Methods

ins :: MonadPlus m :- Alternative (WrappedMonad m)

MonadPlus f => MonadPlus (Rec1 f)

Since: base-4.9.0.0

Defined in GHC.Generics

Methods

mzero :: Rec1 f a

mplus :: Rec1 f a -> Rec1 f a -> Rec1 f a

MonadPlus f => MonadPlus (Alt f)

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)

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)

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)

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)

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 m => MonadPlus (StateT s m)

Defined in Control.Monad.Trans.State.Lazy

Methods

mzero :: StateT s m a

mplus :: StateT s m a -> StateT s m a -> StateT s m a

MonadPlus m => MonadPlus (StateT s m)

Defined in Control.Monad.Trans.State.Strict

Methods

mzero :: StateT s m a

mplus :: StateT s m a -> StateT s m a -> StateT s m a

MonadPlus f => MonadPlus (Star f a)

Defined in Data.Profunctor.Types

Methods

mzero :: Star f a a0

mplus :: Star f a a0 -> Star f a a0 -> Star f a a0

(Functor m, MonadPlus m) => MonadPlus (WriterT w m)

Defined in Control.Monad.Trans.Writer.CPS.Internal

Methods

mzero :: WriterT w m a

mplus :: WriterT w m a -> WriterT w m a -> WriterT w m a

Class (Monad f, Alternative f) (MonadPlus f)

Defined in Data.Constraint

Methods

cls :: MonadPlus f :- (Monad f, Alternative f)

(MonadPlus f, MonadPlus g) => MonadPlus (f :*: g)

Since: base-4.9.0.0

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

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 m => MonadPlus (ReaderT r m)

Defined in Control.Monad.Trans.Reader

Methods

mzero :: ReaderT r m a

mplus :: ReaderT r m a -> ReaderT r m a -> ReaderT r m a

(Ord e, Stream s) => MonadPlus (ParsecT e s m)

mzero is a parser that fails without consuming input.

Defined in Text.Megaparsec.Internal

Methods

mzero :: ParsecT e s m a

mplus :: ParsecT e s m a -> ParsecT e s m a -> ParsecT e s m a

MonadPlus f => MonadPlus (M1 i c f)

Since: base-4.9.0.0

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

endBy :: MonadPlus m => m a -> m sep -> m [a]

endBy p sep parses zero or more occurrences of p, separated and ended by sep. Returns a list of values returned by p.

cStatements = cStatement `endBy` semicolon

endBy1 :: MonadPlus m => m a -> m sep -> m (NonEmpty a)

endBy1 p sep parses one or more occurrences of p, separated and ended by sep. Returns a non-empty list of values returned by p.

many :: MonadPlus m => m a -> m [a]

many p applies the parser p zero or more times and returns a list of the values returned by p.

identifier = (:) <$> letter <*> many (alphaNumChar <|> char '_')

mfilter :: MonadPlus m => (a -> Bool) -> m a -> m a

Direct MonadPlus equivalent of filter filter = (mfilter:: (a -> Bool) -> [a] -> [a] applicable to any MonadPlus, for example mfilter odd (Just 1) == Just 1 mfilter odd (Just 2) == Nothing

sepBy1 :: MonadPlus m => m a -> m sep -> m (NonEmpty a)

sepBy1 p sep parses one or more occurrences of p, separated by sep. Returns a non-empty list of values returned by p.

sepEndBy1 :: MonadPlus m => m a -> m sep -> m (NonEmpty a)

sepEndBy1 p sep parses one or more occurrences of p, separated and optionally ended by sep. Returns a non-empty list of values returned by p.

someTill :: MonadPlus m => m a -> m end -> m (NonEmpty a)

someTill p end works similarly to manyTill p end, but p should succeed at least once.

See also: skipSome, skipSomeTill.

manyTill :: MonadPlus m => m a -> m end -> m [a]

manyTill p end applies parser p zero or more times until parser end succeeds. Returns the list of values returned by p.

See also: skipMany, skipManyTill.

sepBy :: MonadPlus m => m a -> m sep -> m [a]

sepBy p sep parses zero or more occurrences of p, separated by sep. Returns a list of values returned by p.

commaSep p = p `sepBy` comma

sepEndBy :: MonadPlus m => m a -> m sep -> m [a]

sepEndBy p sep parses zero or more occurrences of p, separated and optionally ended by sep. Returns a list of values returned by p.

skipMany :: MonadPlus m => m a -> m ()

skipMany p applies the parser p zero or more times, skipping its result.

See also: manyTill, skipManyTill.

skipManyTill :: MonadPlus m => m a -> m end -> m end

skipManyTill p end applies the parser p zero or more times skipping results until parser end succeeds. Result parsed by end is then returned.

See also: manyTill, skipMany.

skipSome :: MonadPlus m => m a -> m ()

skipSome p applies the parser p one or more times, skipping its result.

See also: someTill, skipSomeTill.

skipSomeTill :: MonadPlus m => m a -> m end -> m end

skipSomeTill p end applies the parser p one or more times skipping results until parser end succeeds. Result parsed by end is then returned.

See also: someTill, skipSome.