Safe Haskell	None
Language	Haskell2010

ListT

Contents

Execution utilities
Construction utilities
Transformation utilities

Synopsis

newtype ListT m a = ListT (m ( Maybe (a, ListT m a)))
uncons :: ListT m a -> m ( Maybe (a, ListT m a))
head :: Monad m => ListT m a -> m ( Maybe a)
tail :: Monad m => ListT m a -> m ( Maybe ( ListT m a))
null :: Monad m => ListT m a -> m Bool
alternate :: ( Alternative m, Monad m) => ListT m a -> m a
alternateHoisting :: ( Monad n, Alternative n) => ( forall a. m a -> n a) -> ListT m a -> n a
fold :: Monad m => (b -> a -> m b) -> b -> ListT m a -> m b
foldMaybe :: Monad m => (b -> a -> m ( Maybe b)) -> b -> ListT m a -> m b
applyFoldM :: Monad m => FoldM m i o -> ListT m i -> m o
toList :: Monad m => ListT m a -> m [a]
toReverseList :: Monad m => ListT m a -> m [a]
traverse_ :: Monad m => (a -> m ()) -> ListT m a -> m ()
splitAt :: Monad m => Int -> ListT m a -> m ([a], ListT m a)
cons :: Monad m => a -> ListT m a -> ListT m a
fromFoldable :: ( Monad m, Foldable f) => f a -> ListT m a
fromMVar :: MonadIO m => MVar ( Maybe a) -> ListT m a
unfold :: Monad m => (b -> Maybe (a, b)) -> b -> ListT m a
unfoldM :: Monad m => (b -> m ( Maybe (a, b))) -> b -> ListT m a
repeat :: Monad m => a -> ListT m a
traverse :: Monad m => (a -> m b) -> ListT m a -> ListT m b
take :: Monad m => Int -> ListT m a -> ListT m a
drop :: Monad m => Int -> ListT m a -> ListT m a
slice :: Monad m => Int -> ListT m a -> ListT m [a]

Documentation

newtype ListT m a Source #

A proper implementation of the list monad-transformer. Useful for streaming of monadic data structures.

Since it has instances of MonadPlus and Alternative , you can use general utilities packages like "monadplus" with it.

Constructors

ListT (m ( Maybe (a, ListT m a)))

Instances

Instances details

MMonad ListT Source #
Instance details Defined in ListT Methods embed :: forall (n :: Type -> Type ) m b. Monad n => ( forall a. m a -> ListT n a) -> ListT m b -> ListT n b Source #
MonadTrans ListT Source #
Instance details Defined in ListT Methods lift :: Monad m => m a -> ListT m a Source #
MonadBase b m => MonadBase b ( ListT m) Source #
Instance details Defined in ListT Methods liftBase :: b α -> ListT m α Source #
MonadBaseControl b m => MonadBaseControl b ( ListT m) Source #
Instance details Defined in ListT Associated Types type StM ( ListT m) a Source # Methods liftBaseWith :: ( RunInBase ( ListT m) b -> b a) -> ListT m a Source # restoreM :: StM ( ListT m) a -> ListT m a Source #
MonadState e m => MonadState e ( ListT m) Source #
Instance details Defined in ListT Methods get :: ListT m e Source # put :: e -> ListT m () Source # state :: (e -> (a, e)) -> ListT m a Source #
MonadReader e m => MonadReader e ( ListT m) Source #
Instance details Defined in ListT Methods ask :: ListT m e Source # local :: (e -> e) -> ListT m a -> ListT m a Source # reader :: (e -> a) -> ListT m a Source #
MonadError e m => MonadError e ( ListT m) Source #
Instance details Defined in ListT Methods throwError :: e -> ListT m a Source # catchError :: ListT m a -> (e -> ListT m a) -> ListT m a Source #
Monad m => Monad ( ListT m) Source #
Instance details Defined in ListT Methods (>>=) :: ListT m a -> (a -> ListT m b) -> ListT m b Source # (>>) :: ListT m a -> ListT m b -> ListT m b Source # return :: a -> ListT m a Source #
Functor m => Functor ( ListT m) Source #
Instance details Defined in ListT Methods fmap :: (a -> b) -> ListT m a -> ListT m b Source # (<$) :: a -> ListT m b -> ListT m a Source #
Monad m => MonadFail ( ListT m) Source #
Instance details Defined in ListT Methods fail :: String -> ListT m a Source #
( Monad m, Functor m) => Applicative ( ListT m) Source #
Instance details Defined in ListT Methods pure :: a -> ListT m a Source # (<>) :: ListT m (a -> b) -> ListT m a -> ListT m b Source # liftA2 :: (a -> b -> c) -> ListT m a -> ListT m b -> ListT m c Source # (>) :: ListT m a -> ListT m b -> ListT m b Source # (<*) :: ListT m a -> ListT m b -> ListT m a Source #
Foldable m => Foldable ( ListT m) Source #
Instance details Defined in ListT Methods fold :: Monoid m0 => ListT m m0 -> m0 Source # foldMap :: Monoid m0 => (a -> m0) -> ListT m a -> m0 Source # foldMap' :: Monoid m0 => (a -> m0) -> ListT m a -> m0 Source # foldr :: (a -> b -> b) -> b -> ListT m a -> b Source # foldr' :: (a -> b -> b) -> b -> ListT m a -> b Source # foldl :: (b -> a -> b) -> b -> ListT m a -> b Source # foldl' :: (b -> a -> b) -> b -> ListT m a -> b Source # foldr1 :: (a -> a -> a) -> ListT m a -> a Source # foldl1 :: (a -> a -> a) -> ListT m a -> a Source # toList :: ListT m a -> [a] Source # null :: ListT m a -> Bool Source # length :: ListT m a -> Int Source # elem :: Eq a => a -> ListT m a -> Bool Source # maximum :: Ord a => ListT m a -> a Source # minimum :: Ord a => ListT m a -> a Source # sum :: Num a => ListT m a -> a Source # product :: Num a => ListT m a -> a Source #
Traversable m => Traversable ( ListT m) Source #
Instance details Defined in ListT Methods traverse :: Applicative f => (a -> f b) -> ListT m a -> f ( ListT m b) Source # sequenceA :: Applicative f => ListT m (f a) -> f ( ListT m a) Source # mapM :: Monad m0 => (a -> m0 b) -> ListT m a -> m0 ( ListT m b) Source # sequence :: Monad m0 => ListT m (m0 a) -> m0 ( ListT m a) Source #
Eq1 m => Eq1 ( ListT m) Source #
Instance details Defined in ListT Methods liftEq :: (a -> b -> Bool ) -> ListT m a -> ListT m b -> Bool Source #
Ord1 m => Ord1 ( ListT m) Source #
Instance details Defined in ListT Methods liftCompare :: (a -> b -> Ordering ) -> ListT m a -> ListT m b -> Ordering Source #
Show1 m => Show1 ( ListT m) Source #
Instance details Defined in ListT Methods liftShowsPrec :: ( Int -> a -> ShowS ) -> ([a] -> ShowS ) -> Int -> ListT m a -> ShowS Source # liftShowList :: ( Int -> a -> ShowS ) -> ([a] -> ShowS ) -> [ ListT m a] -> ShowS Source #
MonadZip m => MonadZip ( ListT m) Source #
Instance details Defined in ListT Methods mzip :: ListT m a -> ListT m b -> ListT m (a, b) Source # mzipWith :: (a -> b -> c) -> ListT m a -> ListT m b -> ListT m c Source # munzip :: ListT m (a, b) -> ( ListT m a, ListT m b) Source #
MonadIO m => MonadIO ( ListT m) Source #
Instance details Defined in ListT Methods liftIO :: IO a -> ListT m a Source #
( Monad m, Functor m) => Alternative ( ListT m) Source #
Instance details Defined in ListT Methods empty :: ListT m a Source # (<\|>) :: ListT m a -> ListT m a -> ListT m a Source # some :: ListT m a -> ListT m [a] Source # many :: ListT m a -> ListT m [a] Source #
Monad m => MonadPlus ( ListT m) Source #
Instance details Defined in ListT Methods mzero :: ListT m a Source # mplus :: ListT m a -> ListT m a -> ListT m a Source #
Monad m => MonadLogic ( ListT m) Source #
Instance details Defined in ListT Methods msplit :: ListT m a -> ListT m ( Maybe (a, ListT m a)) Source # interleave :: ListT m a -> ListT m a -> ListT m a Source # (>>-) :: ListT m a -> (a -> ListT m b) -> ListT m b Source # once :: ListT m a -> ListT m a Source # lnot :: ListT m a -> ListT m () Source # ifte :: ListT m a -> (a -> ListT m b) -> ListT m b -> ListT m b Source #
MFunctor ListT Source #
Instance details Defined in ListT Methods hoist :: forall m n (b :: k). Monad m => ( forall a. m a -> n a) -> ListT m b -> ListT n b Source #
Eq (m ( Maybe (a, ListT m a))) => Eq ( ListT m a) Source #
Instance details Defined in ListT Methods (==) :: ListT m a -> ListT m a -> Bool Source # (/=) :: ListT m a -> ListT m a -> Bool Source #
( Typeable m, Typeable a, Data (m ( Maybe (a, ListT m a)))) => Data ( ListT m a) Source #
Instance details Defined in ListT Methods gfoldl :: ( forall d b. Data d => c (d -> b) -> d -> c b) -> ( forall g. g -> c g) -> ListT m a -> c ( ListT m a) Source # gunfold :: ( forall b r. Data b => c (b -> r) -> c r) -> ( forall r. r -> c r) -> Constr -> c ( ListT m a) Source # toConstr :: ListT m a -> Constr Source # dataTypeOf :: ListT m a -> DataType Source # dataCast1 :: Typeable t => ( forall d. Data d => c (t d)) -> Maybe (c ( ListT m a)) Source # dataCast2 :: Typeable t => ( forall d e. ( Data d, Data e) => c (t d e)) -> Maybe (c ( ListT m a)) Source # gmapT :: ( forall b. Data b => b -> b) -> ListT m a -> ListT m a Source # gmapQl :: (r -> r' -> r) -> r -> ( forall d. Data d => d -> r') -> ListT m a -> r Source # gmapQr :: forall r r'. (r' -> r -> r) -> r -> ( forall d. Data d => d -> r') -> ListT m a -> r Source # gmapQ :: ( forall d. Data d => d -> u) -> ListT m a -> [u] Source # gmapQi :: Int -> ( forall d. Data d => d -> u) -> ListT m a -> u Source # gmapM :: Monad m0 => ( forall d. Data d => d -> m0 d) -> ListT m a -> m0 ( ListT m a) Source # gmapMp :: MonadPlus m0 => ( forall d. Data d => d -> m0 d) -> ListT m a -> m0 ( ListT m a) Source # gmapMo :: MonadPlus m0 => ( forall d. Data d => d -> m0 d) -> ListT m a -> m0 ( ListT m a) Source #
Ord (m ( Maybe (a, ListT m a))) => Ord ( ListT m a) Source #
Instance details Defined in ListT Methods compare :: ListT m a -> ListT m a -> Ordering Source # (<) :: ListT m a -> ListT m a -> Bool Source # (<=) :: ListT m a -> ListT m a -> Bool Source # (>) :: ListT m a -> ListT m a -> Bool Source # (>=) :: ListT m a -> ListT m a -> Bool Source # max :: ListT m a -> ListT m a -> ListT m a Source # min :: ListT m a -> ListT m a -> ListT m a Source #
Read (m ( Maybe (a, ListT m a))) => Read ( ListT m a) Source #
Instance details Defined in ListT Methods readsPrec :: Int -> ReadS ( ListT m a) Source # readList :: ReadS [ ListT m a] Source # readPrec :: ReadPrec ( ListT m a) Source # readListPrec :: ReadPrec [ ListT m a] Source #
Show (m ( Maybe (a, ListT m a))) => Show ( ListT m a) Source #
Instance details Defined in ListT Methods showsPrec :: Int -> ListT m a -> ShowS Source # show :: ListT m a -> String Source # showList :: [ ListT m a] -> ShowS Source #
Generic ( ListT m a) Source #
Instance details Defined in ListT Associated Types type Rep ( ListT m a) :: Type -> Type Source # Methods from :: ListT m a -> Rep ( ListT m a) x Source # to :: Rep ( ListT m a) x -> ListT m a Source #
Monad m => Semigroup ( ListT m a) Source #
Instance details Defined in ListT Methods (<>) :: ListT m a -> ListT m a -> ListT m a Source # sconcat :: NonEmpty ( ListT m a) -> ListT m a Source # stimes :: Integral b => b -> ListT m a -> ListT m a Source #
Monad m => Monoid ( ListT m a) Source #
Instance details Defined in ListT Methods mempty :: ListT m a Source # mappend :: ListT m a -> ListT m a -> ListT m a Source # mconcat :: [ ListT m a] -> ListT m a Source #
type StM ( ListT m) a Source #
Instance details Defined in ListT type StM ( ListT m) a = StM m ( Maybe (a, ListT m a))
type Rep ( ListT m a) Source #
Instance details Defined in ListT type Rep ( ListT m a) = D1 (' MetaData "ListT" "ListT" "list-t-1.0.5.6-wkEaNz8lcH7c6HMGWeDwC" ' True ) ( C1 (' MetaCons "ListT" ' PrefixI ' False ) ( S1 (' MetaSel (' Nothing :: Maybe Symbol ) ' NoSourceUnpackedness ' NoSourceStrictness ' DecidedLazy ) ( Rec0 (m ( Maybe (a, ListT m a))))))

Execution utilities

uncons :: ListT m a -> m ( Maybe (a, ListT m a)) Source #

Execute in the inner monad, getting the head and the tail. Returns nothing if it's empty.

head :: Monad m => ListT m a -> m ( Maybe a) Source #

Execute, getting the head. Returns nothing if it's empty.

tail :: Monad m => ListT m a -> m ( Maybe ( ListT m a)) Source #

Execute, getting the tail. Returns nothing if it's empty.

null :: Monad m => ListT m a -> m Bool Source #

Execute, checking whether it's empty.

alternate :: ( Alternative m, Monad m) => ListT m a -> m a Source #

Execute in the inner monad, using its (<|>) function on each entry.

alternateHoisting :: ( Monad n, Alternative n) => ( forall a. m a -> n a) -> ListT m a -> n a Source #

Use a monad morphism to convert a ListT to a similar monad, such as '[]'.

A more efficient alternative to alternate . hoist f .

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

Execute, applying a strict left fold.

foldMaybe :: Monad m => (b -> a -> m ( Maybe b)) -> b -> ListT m a -> m b Source #

A version of fold , which allows early termination.

applyFoldM :: Monad m => FoldM m i o -> ListT m i -> m o Source #

Apply the left fold abstraction from the "foldl" package.

toList :: Monad m => ListT m a -> m [a] Source #

Execute, folding to a list.

toReverseList :: Monad m => ListT m a -> m [a] Source #

Execute, folding to a list in the reverse order. Performs more efficiently than toList .

traverse_ :: Monad m => (a -> m ()) -> ListT m a -> m () Source #

Execute, traversing the stream with a side effect in the inner monad.

splitAt :: Monad m => Int -> ListT m a -> m ([a], ListT m a) Source #

Execute, consuming a list of the specified length and returning the remainder stream.

Construction utilities

cons :: Monad m => a -> ListT m a -> ListT m a Source #

Prepend an element.

fromFoldable :: ( Monad m, Foldable f) => f a -> ListT m a Source #

Construct from any foldable.

fromMVar :: MonadIO m => MVar ( Maybe a) -> ListT m a Source #

Construct from an MVar, interpreting the value of Nothing as the end.

unfold :: Monad m => (b -> Maybe (a, b)) -> b -> ListT m a Source #

Construct by unfolding a pure data structure.

unfoldM :: Monad m => (b -> m ( Maybe (a, b))) -> b -> ListT m a Source #

Construct by unfolding a monadic data structure

This is the most memory-efficient way to construct ListT where the length depends on the inner monad.

repeat :: Monad m => a -> ListT m a Source #

Produce an infinite stream.

Transformation utilities

These utilities only accumulate the transformations without actually traversing the stream. They only get applied in a single traversal, which only happens at the execution.

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

A transformation, which traverses the stream with an action in the inner monad.

take :: Monad m => Int -> ListT m a -> ListT m a Source #

A transformation, reproducing the behaviour of Data.List. take .

drop :: Monad m => Int -> ListT m a -> ListT m a Source #

A transformation, reproducing the behaviour of Data.List. drop .

slice :: Monad m => Int -> ListT m a -> ListT m [a] Source #

A transformation, which slices a list into chunks of the specified length.