Streamly.Internal.Data.Stream.StreamD.Transformer

Transform the underlying monad of a stream using a monad transfomer.

Documentation

foldlT :: (Monad m, Monad (s m), MonadTrans s) => (s m b -> a -> s m b) -> s m b -> Stream m a -> s m b

Lazy left fold to a transformer monad.

foldrT :: (Monad m, Monad (t m), MonadTrans t) => (a -> t m b -> t m b) -> t m b -> Stream m a -> t m b

Right fold to a transformer monad. This is the most general right fold function. foldrS is a special case of foldrT, however foldrS implementation can be more efficient:

>>> foldrS = Stream.foldrT

>>> step f x xs = lift $ f x (runIdentityT xs)
>>> foldrM f z s = runIdentityT $ Stream.foldrT (step f) (lift z) s

foldrT can be used to translate streamly streams to other transformer monads e.g. to a different streaming type.

Pre-release

Transform Inner Monad

liftInner :: (Monad m, MonadTrans t, Monad (t m)) => Stream m a -> Stream (t m) a

Lift the inner monad m of Stream m a to t m where t is a monad transformer.

runReaderT :: Monad m => m s -> Stream (ReaderT s m) a -> Stream m a

Evaluate the inner monad of a stream as ReaderT.

usingReaderT :: Monad m => m r -> (Stream (ReaderT r m) a -> Stream (ReaderT r m) a) -> Stream m a -> Stream m a

Run a stream transformation using a given environment.

evalStateT :: Monad m => m s -> Stream (StateT s m) a -> Stream m a

Evaluate the inner monad of a stream as StateT.

>>> evalStateT s = fmap snd . Stream.runStateT s

runStateT :: Monad m => m s -> Stream (StateT s m) a -> Stream m (s, a)

Evaluate the inner monad of a stream as StateT and emit the resulting state and value pair after each step.

usingStateT :: Monad m => m s -> (Stream (StateT s m) a -> Stream (StateT s m) a) -> Stream m a -> Stream m a

Run a stateful (StateT) stream transformation using a given state.

>>> usingStateT s f = Stream.evalStateT s . f . Stream.liftInner

See also: scan