Capability.Stream

Defines a capability for computations that produce a stream of values as part of their execution.

Programs producing streams of data are common. Examples: emitting events on input, or emitting events whenever certain conditions are observed. Streams are similar to Python generators.

The HasStream capability enables separating the logic responsible for emitting events from that responsible for collecting or handling them.

This can be thought of as a writer capability of a list of values HasWriter tag [v] with \x -> tell @tag [x] as a primitive operation. However, that implementation would be inefficient.

For example using the Stream instance, a producer defined using this capability can be consumed efficiently in a streaming fashion.

Interface

class Monad m => HasStream (tag :: k) (a :: *) (m :: * -> *) | tag m -> a where

Streaming capability.

An instance does not need to fulfill any additional laws besides the monad laws.

Methods

yield_ :: Proxy# tag -> a -> m ()

For technical reasons, this method needs an extra proxy argument. You only need it if you are defining new instances of HasReader. Otherwise, you will want to use yield. See yield for more documentation.

Instances

(HasStream tag a m, MonadTrans t, Monad (t m)) => HasStream (tag :: k) a (Lift (t m))

Lift one layer in a monad transformer stack.

Defined in Capability.Stream

Methods

yield_ :: Proxy# tag -> a -> Lift (t m) ()

HasState tag [a] m => HasStream (tag :: k) a (StreamStack m)

Defined in Capability.Stream

Methods

yield_ :: Proxy# tag -> a -> StreamStack m ()

HasWriter tag (DList a) m => HasStream (tag :: k) a (StreamDList m)

Defined in Capability.Stream

Methods

yield_ :: Proxy# tag -> a -> StreamDList m ()

Monad m => HasStream (tag :: k) a (Stream (Of a) m)

Defined in Capability.Stream

Methods

yield_ :: Proxy# tag -> a -> Stream (Of a) m ()

(forall x. Coercible (m x) (t2 (t1 m) x), Monad m, HasStream tag a (t2 (t1 m))) => HasStream (tag :: k) a ((t2 :.: t1) m)

Compose two accessors.

Defined in Capability.Stream

Methods

yield_ :: Proxy# tag -> a -> (t2 :.: t1) m ()

yield :: forall tag a m. HasStream tag a m => a -> m ()

yield @tag a emits a in the stream capability tag.

Strategies

newtype StreamStack m (a :: *)

Accumulate streamed values in a reverse order list.

Constructors

StreamStack (m a)

Instances

HasState tag [a] m => HasStream (tag :: k) a (StreamStack m)

Defined in Capability.Stream

Methods

yield_ :: Proxy# tag -> a -> StreamStack m ()

Monad m => Monad (StreamStack m)

Defined in Capability.Stream

Methods

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

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

return :: a -> StreamStack m a

fail :: String -> StreamStack m a

Functor m => Functor (StreamStack m)

Defined in Capability.Stream

Methods

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

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

Applicative m => Applicative (StreamStack m)

Defined in Capability.Stream

Methods

pure :: a -> StreamStack m a

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

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

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

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

MonadIO m => MonadIO (StreamStack m)

Defined in Capability.Stream

Methods

liftIO :: IO a -> StreamStack m a

PrimMonad m => PrimMonad (StreamStack m)

Defined in Capability.Stream

Associated Types

type PrimState (StreamStack m) :: Type

Methods

primitive :: (State# (PrimState (StreamStack m)) -> (#State# (PrimState (StreamStack m)), a#)) -> StreamStack m a

type PrimState (StreamStack m)

Defined in Capability.Stream

type PrimState (StreamStack m) = PrimState m

newtype StreamDList m (a :: *)

Accumulate streamed values in forward order in a difference list.

Constructors

StreamDList (m a)

Instances

HasWriter tag (DList a) m => HasStream (tag :: k) a (StreamDList m)

Defined in Capability.Stream

Methods

yield_ :: Proxy# tag -> a -> StreamDList m ()

Monad m => Monad (StreamDList m)

Defined in Capability.Stream

Methods

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

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

return :: a -> StreamDList m a

fail :: String -> StreamDList m a

Functor m => Functor (StreamDList m)

Defined in Capability.Stream

Methods

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

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

Applicative m => Applicative (StreamDList m)

Defined in Capability.Stream

Methods

pure :: a -> StreamDList m a

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

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

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

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

MonadIO m => MonadIO (StreamDList m)

Defined in Capability.Stream

Methods

liftIO :: IO a -> StreamDList m a

PrimMonad m => PrimMonad (StreamDList m)

Defined in Capability.Stream

Associated Types

type PrimState (StreamDList m) :: Type

Methods

primitive :: (State# (PrimState (StreamDList m)) -> (#State# (PrimState (StreamDList m)), a#)) -> StreamDList m a

type PrimState (StreamDList m)

Defined in Capability.Stream

type PrimState (StreamDList m) = PrimState m

Modifiers

module Capability.Accessors