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

MonadTrans ListT Source #
Instance details Defined in ListT Methods lift :: Monad m => m a -> ListT m a #
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 #
MonadBase b m => MonadBase b (ListT m) Source #
Instance details Defined in ListT Methods liftBase :: b α -> ListT m α #
MonadBaseControl b m => MonadBaseControl b (ListT m) Source #
Instance details 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 #
MonadState e m => MonadState e (ListT m) Source #
Instance details Defined in ListT Methods get :: ListT m e # put :: e -> ListT m () # state :: (e -> (a, e)) -> ListT m a #
MonadReader e m => MonadReader e (ListT m) Source #
Instance details Defined in ListT Methods ask :: ListT m e # local :: (e -> e) -> ListT m a -> ListT m a # reader :: (e -> a) -> ListT m a #
MonadError e m => MonadError e (ListT m) Source #
Instance details Defined in ListT Methods throwError :: e -> ListT m a # catchError :: ListT m a -> (e -> ListT m a) -> ListT m a #
Monad m => Monad (ListT m) Source #
Instance details 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 #
Functor m => Functor (ListT m) Source #
Instance details Defined in ListT Methods fmap :: (a -> b) -> ListT m a -> ListT m b # (<$) :: a -> ListT m b -> ListT m a #
Monad m => MonadFail (ListT m) Source #
Instance details Defined in ListT Methods fail :: String -> ListT m a #
(Monad m, Functor m) => Applicative (ListT m) Source #
Instance details 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 #
Foldable m => Foldable (ListT m) Source #
Instance details 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 #
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) # 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) #
Eq1 m => Eq1 (ListT m) Source #
Instance details Defined in ListT Methods liftEq :: (a -> b -> Bool) -> ListT m a -> ListT m b -> Bool #
Ord1 m => Ord1 (ListT m) Source #
Instance details Defined in ListT Methods liftCompare :: (a -> b -> Ordering) -> ListT m a -> ListT m b -> Ordering #
Show1 m => Show1 (ListT m) Source #
Instance details 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 #
MonadZip m => MonadZip (ListT m) Source #
Instance details 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) #
MonadIO m => MonadIO (ListT m) Source #
Instance details Defined in ListT Methods liftIO :: IO a -> ListT m a #
(Monad m, Functor m) => Alternative (ListT m) Source #
Instance details 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 => MonadPlus (ListT m) Source #
Instance details Defined in ListT Methods mzero :: ListT m a # mplus :: ListT m a -> ListT m a -> ListT m a #
Monad m => MonadLogic (ListT m) Source #
Instance details 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 # ifte :: ListT m a -> (a -> ListT m b) -> ListT m b -> ListT m b # once :: ListT m a -> ListT m a # lnot :: ListT m a -> ListT m () #
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 #
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 # (/=) :: ListT m a -> ListT m a -> Bool #
(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) # 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) #
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 # (<) :: 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 #
Read (m (Maybe (a, ListT m a))) => Read (ListT m a) Source #
Instance details 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) Source #
Instance details Defined in ListT Methods showsPrec :: Int -> ListT m a -> ShowS # show :: ListT m a -> String # showList :: [ListT m a] -> ShowS #
Generic (ListT m a) Source #
Instance details 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 #
Monad m => Semigroup (ListT m a) Source #
Instance details 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 #
Monad m => Monoid (ListT m a) Source #
Instance details 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 #
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-Ap9FdX6PXClIIL1xeDSF04" '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 => (r -> a -> m r) -> r -> ListT m a -> m r Source #

Execute, applying a left fold.

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

A version of fold, which allows early termination.

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

Apply a 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.