ListT

Documentation

newtype ListT m a

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

MMonad ListT

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

MonadTrans ListT

Defined in ListT

Methods

lift :: Monad m => m a -> ListT m a

MFunctor ListT

Defined in ListT

Methods

hoist :: forall m n (b :: k). Monad m => (forall a. m a -> n a) -> ListT m b -> ListT n b

MonadBaseControl b m => MonadBaseControl b (ListT m)

Defined in ListT

Associated Types

type StM (ListT m) a

Methods

liftBaseWith :: (RunInBase (ListT m) b -> b a) -> ListT m a

restoreM :: StM (ListT m) a -> ListT m a

MonadError e m => MonadError e (ListT m)

Defined in ListT

Methods

throwError :: e -> ListT m a

catchError :: ListT m a -> (e -> ListT m a) -> ListT m a

MonadReader e m => MonadReader e (ListT m)

Defined in ListT

Methods

ask :: ListT m e

local :: (e -> e) -> ListT m a -> ListT m a

reader :: (e -> a) -> ListT m a

MonadState e m => MonadState e (ListT m)

Defined in ListT

Methods

get :: ListT m e

put :: e -> ListT m ()

state :: (e -> (a, e)) -> ListT m a

MonadBase b m => MonadBase b (ListT m)

Defined in ListT

Methods

liftBase :: b α -> ListT m α

Monad m => MonadFail (ListT m)

Defined in ListT

Methods

fail :: String -> ListT m a

MonadIO m => MonadIO (ListT m)

Defined in ListT

Methods

liftIO :: IO a -> ListT m a

MonadZip m => MonadZip (ListT m)

Defined in ListT

Methods

mzip :: ListT m a -> ListT m b -> ListT m (a, b)

mzipWith :: (a -> b -> c) -> ListT m a -> ListT m b -> ListT m c

munzip :: ListT m (a, b) -> (ListT m a, ListT m b)

Foldable m => Foldable (ListT m)

Defined in ListT

Methods

fold :: Monoid m0 => ListT m m0 -> m0

foldMap :: Monoid m0 => (a -> m0) -> ListT m a -> m0

foldMap' :: Monoid m0 => (a -> m0) -> ListT m a -> m0

foldr :: (a -> b -> b) -> b -> ListT m a -> b

foldr' :: (a -> b -> b) -> b -> ListT m a -> b

foldl :: (b -> a -> b) -> b -> ListT m a -> b

foldl' :: (b -> a -> b) -> b -> ListT m a -> b

foldr1 :: (a -> a -> a) -> ListT m a -> a

foldl1 :: (a -> a -> a) -> ListT m a -> a

toList :: ListT m a -> [a]

null :: ListT m a -> Bool

length :: ListT m a -> Int

elem :: Eq a => a -> ListT m a -> Bool

maximum :: Ord a => ListT m a -> a

minimum :: Ord a => ListT m a -> a

sum :: Num a => ListT m a -> a

product :: Num a => ListT m a -> a

Eq1 m => Eq1 (ListT m)

Defined in ListT

Methods

liftEq :: (a -> b -> Bool) -> ListT m a -> ListT m b -> Bool

Ord1 m => Ord1 (ListT m)

Defined in ListT

Methods

liftCompare :: (a -> b -> Ordering) -> ListT m a -> ListT m b -> Ordering

Show1 m => Show1 (ListT m)

Defined in ListT

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> ListT m a -> ShowS

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [ListT m a] -> ShowS

Traversable m => Traversable (ListT m)

Defined in ListT

Methods

traverse :: Applicative f => (a -> f b) -> ListT m a -> f (ListT m b)

sequenceA :: Applicative f => ListT m (f a) -> f (ListT m a)

mapM :: Monad m0 => (a -> m0 b) -> ListT m a -> m0 (ListT m b)

sequence :: Monad m0 => ListT m (m0 a) -> m0 (ListT m a)

(Monad m, Functor m) => Alternative (ListT m)

Defined in ListT

Methods

empty :: ListT m a

(<|>) :: ListT m a -> ListT m a -> ListT m a

some :: ListT m a -> ListT m [a]

many :: ListT m a -> ListT m [a]

(Monad m, Functor m) => Applicative (ListT m)

Defined in ListT

Methods

pure :: a -> ListT m a

(<*>) :: ListT m (a -> b) -> ListT m a -> ListT m b

liftA2 :: (a -> b -> c) -> ListT m a -> ListT m b -> ListT m c

(*>) :: ListT m a -> ListT m b -> ListT m b

(<*) :: ListT m a -> ListT m b -> ListT m a

Functor m => Functor (ListT m)

Defined in ListT

Methods

fmap :: (a -> b) -> ListT m a -> ListT m b

(<$) :: a -> ListT m b -> ListT m a

Monad m => Monad (ListT m)

Defined in ListT

Methods

(>>=) :: ListT m a -> (a -> ListT m b) -> ListT m b

(>>) :: ListT m a -> ListT m b -> ListT m b

return :: a -> ListT m a

Monad m => MonadPlus (ListT m)

Defined in ListT

Methods

mzero :: ListT m a

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

Monad m => MonadLogic (ListT m)

Defined in ListT

Methods

msplit :: ListT m a -> ListT m (Maybe (a, ListT m a))

interleave :: ListT m a -> ListT m a -> ListT m a

(>>-) :: ListT m a -> (a -> ListT m b) -> ListT m b

once :: ListT m a -> ListT m a

lnot :: ListT m a -> ListT m ()

ifte :: ListT m a -> (a -> ListT m b) -> ListT m b -> ListT m b

(Typeable m, Typeable a, Data (m (Maybe (a, ListT m a)))) => Data (ListT m a)

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)

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (ListT m a)

toConstr :: ListT m a -> Constr

dataTypeOf :: ListT m a -> DataType

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (ListT m a))

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (ListT m a))

gmapT :: (forall b. Data b => b -> b) -> ListT m a -> ListT m a

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> ListT m a -> r

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> ListT m a -> r

gmapQ :: (forall d. Data d => d -> u) -> ListT m a -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> ListT m a -> u

gmapM :: Monad m0 => (forall d. Data d => d -> m0 d) -> ListT m a -> m0 (ListT m a)

gmapMp :: MonadPlus m0 => (forall d. Data d => d -> m0 d) -> ListT m a -> m0 (ListT m a)

gmapMo :: MonadPlus m0 => (forall d. Data d => d -> m0 d) -> ListT m a -> m0 (ListT m a)

Monad m => Monoid (ListT m a)

Defined in ListT

Methods

mempty :: ListT m a

mappend :: ListT m a -> ListT m a -> ListT m a

mconcat :: [ListT m a] -> ListT m a

Monad m => Semigroup (ListT m a)

Defined in ListT

Methods

(<>) :: ListT m a -> ListT m a -> ListT m a

sconcat :: NonEmpty (ListT m a) -> ListT m a

stimes :: Integral b => b -> ListT m a -> ListT m a

Generic (ListT m a)

Defined in ListT

Associated Types

type Rep (ListT m a) :: Type -> Type

Methods

from :: ListT m a -> Rep (ListT m a) x

to :: Rep (ListT m a) x -> ListT m a

Read (m (Maybe (a, ListT m a))) => Read (ListT m a)

Defined in ListT

Methods

readsPrec :: Int -> ReadS (ListT m a)

readList :: ReadS [ListT m a]

readPrec :: ReadPrec (ListT m a)

readListPrec :: ReadPrec [ListT m a]

Show (m (Maybe (a, ListT m a))) => Show (ListT m a)

Defined in ListT

Methods

showsPrec :: Int -> ListT m a -> ShowS

show :: ListT m a -> String

showList :: [ListT m a] -> ShowS

Eq (m (Maybe (a, ListT m a))) => Eq (ListT m a)

Defined in ListT

Methods

(==) :: ListT m a -> ListT m a -> Bool

(/=) :: ListT m a -> ListT m a -> Bool

Ord (m (Maybe (a, ListT m a))) => Ord (ListT m a)

Defined in ListT

Methods

compare :: ListT m a -> ListT m a -> Ordering

(<) :: ListT m a -> ListT m a -> Bool

(<=) :: ListT m a -> ListT m a -> Bool

(>) :: ListT m a -> ListT m a -> Bool

(>=) :: ListT m a -> ListT m a -> Bool

max :: ListT m a -> ListT m a -> ListT m a

min :: ListT m a -> ListT m a -> ListT m a

type StM (ListT m) a

Defined in ListT

type StM (ListT m) a = StM m (Maybe (a, ListT m a))

type Rep (ListT m a)

Defined in ListT

type Rep (ListT m a) = D1 ('MetaData "ListT" "ListT" "list-t-1.0.5.6-3W9r7IByJvs6hZM41sJEKx" '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))

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)

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

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

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

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

Execute, checking whether it's empty.

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

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

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

Execute, applying a strict left fold.

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

A version of fold, which allows early termination.

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

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

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

Execute, folding to a list.

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

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

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

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

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

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

Prepend an element.

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

Construct from any foldable.

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

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

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

Construct by unfolding a pure data structure.

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

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

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

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

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

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

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

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

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

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