purescript(switcheroo): Simplified types
Signed-off-by: prescientmoon <git@moonythm.dev>
This commit is contained in:
Matei Adriel
parent
a1f2c01651
commit
ca3cb6ae29
SSH key fingerprint:
SHA256:WFp/cO76nbarETAoQcQXuV+0h7XJsEsOCI0UsyPIy6U
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@ -8,7 +8,7 @@ import Data.Identity (Identity(..))
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import Effect (Effect)
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import Effect.Console (log)
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import Safe.Coerce (coerce)
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import Swictheroo.Stream (Finished, Producer, constantProducer, runConsumeM_)
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import Swictheroo.Stream (ConsumeM, Producer, constantProducer, runConsumeM_, unitProducer)
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import Swictheroo.Stream as Stream
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type Producers m =
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@ -17,7 +17,7 @@ type Producers m =
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, ping :: Producer m Boolean
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}
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program :: forall m. Monad m => Producers m -> Finished m String Unit
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program :: forall m. Monad m => Producers m -> ConsumeM m Unit Unit String
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program producers = Ix.do
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Stream.replace producers.download
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a <- Stream.pull
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@ -28,7 +28,9 @@ program producers = Ix.do
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Stream.replace producers.ping
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c <- Stream.pull
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Stream.terminate $ Array.fold
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Stream.replace unitProducer
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pure $ Array.fold
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[ "Download: "
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, show a
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, ", Report: "
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@ -104,7 +106,7 @@ Note that in an actual production codebase we would receive
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allow mocking and to not tie ourselves to a specific monad.
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-}
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{- One could thing about this approach is
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{- One cool thing about this approach is
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that simple state can be kept without the need for StateT!
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(because we can simply pass around values)
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-}
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@ -6,60 +6,60 @@ import Control.Alt (class Alt)
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import Control.Alternative (class Plus, (<|>))
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import Control.Applicative.Indexed (class IxApplicative, class IxApply, class IxFunctor)
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import Control.Bind.Indexed (class IxBind)
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import Control.Monad.Indexed (class IxMonad, iap)
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import Control.Monad.Indexed (class IxMonad, iap, iapply, ibind, imap, ipure)
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import Control.Parallel (parOneOf, parSequence_)
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import Data.Bifunctor (bimap)
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import Data.Either (Either(..))
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import Data.Lazy (Lazy)
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import Data.Lazy as Lazy
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import Data.Maybe (Maybe(..))
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import Data.Profunctor.Strong (first)
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import Data.Tuple.Nested (type (/\), (/\))
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import Effect.Aff (Aff, never)
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-- | A producer can:
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-- | - Produce values
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-- | - Destroy itself
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-- |
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-- | A producer does this by reacting to input events
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-- | in order to satisfy continuations.
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newtype Producer m a =
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Producer (forall c. Monad m => ProducerEvent m c a -> m c)
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data ProducerEvent m c a
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Producer
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{ destroy :: m Unit
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-- | Producers advance to a new version once they produce a value.
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-- | This allows pure producers to exist. For example, a pure producer
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-- | could hold an array of events, return the first one, and then create
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-- | a new producer from the tail of the array
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= Produce (a -> Producer m a -> c)
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| Destroy c
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, produce :: m (Lazy (a /\ Producer m a))
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}
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produce :: forall m i. Monad m => Producer m i -> m (i /\ Producer m i)
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produce (Producer producer) = producer (Produce (/\))
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produce (Producer producer) = producer.produce <#> Lazy.force
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destroyProducer :: forall m i. Monad m => Producer m i -> m Unit
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destroyProducer (Producer producer) = producer (Destroy unit)
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destroyProducer (Producer producer) = producer.destroy
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constantProducer :: forall m a. Monad m => a -> Producer m a
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constantProducer value = Producer case _ of
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Destroy c -> pure c
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Produce next -> pure (next value (constantProducer value))
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constantProducer value = Producer
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{ destroy: pure unit
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, produce: pure $ Lazy.defer \_ -> value /\ (constantProducer value)
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}
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unitProducer :: forall m. Monad m => Producer m Unit
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unitProducer = constantProducer unit
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filterMapProducer :: forall a b m. Monad m => (a -> Maybe b) -> Producer m a -> Producer m b
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filterMapProducer f producer = Producer case _ of
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Destroy c -> destroyProducer producer $> c
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Produce next -> loop producer
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filterMapProducer f producer = Producer
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{ destroy: destroyProducer producer
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, produce: loop producer
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}
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where
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-- Keeps producing values until one matches the given predicate!
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loop producer = do
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value /\ producer' <- produce producer
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case f value of
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Nothing -> loop producer'
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Just updated -> pure (next updated (filterMapProducer f producer'))
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Just updated -> pure $ Lazy.defer \_ -> updated /\ (filterMapProducer f producer')
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-- | Type parameter explanation:
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-- | - m = underlying monad
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-- | - t = type we want to end on
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-- | - i = what the producer present when
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-- | the computation *starts* needs to produce
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-- | - o = what the producer present when
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@ -67,126 +67,101 @@ filterMapProducer f producer = Producer case _ of
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-- | - a = result of the computation
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-- |
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-- | This monad encapsulates the followin 3 operations:
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-- | - Basic continuations (we have a type we want to terminate on)
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-- | - Consuming values from a producer
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-- | - Cancelling + replacing the current producer with a different one.
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newtype ConsumeM m t i o a = ConsumeM
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( forall c
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. { producer :: Producer m i
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, continue :: Producer m o -> a -> m c
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, terminate :: t -> m c
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}
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-> m c
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newtype ConsumeM m i o a = ConsumeM
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( Producer m i -> m (a /\ Producer m o)
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)
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-- | A ConsumeM computation that has finshed running
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type Finished m t i = ConsumeM m t i Void Void
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pull :: forall m i. Monad m => ConsumeM m i i i
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pull = ConsumeM produce
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pull :: forall m t i. Monad m => ConsumeM m t i i i
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pull = ConsumeM \inputs -> do
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i /\ producer' <- produce inputs.producer
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inputs.continue producer' i
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replace :: forall m i o. Monad m => Producer m o -> ConsumeM m i o Unit
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replace producer' = ConsumeM \producer -> do
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destroyProducer producer
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pure (unit /\ producer')
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replace :: forall m t i o. Monad m => Producer m o -> ConsumeM m t i o Unit
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replace producer' = ConsumeM \inputs -> do
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destroyProducer inputs.producer
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inputs.continue producer' unit
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terminate :: forall m t i. Monad m => t -> Finished m t i
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terminate result = ConsumeM \inputs -> do
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destroyProducer inputs.producer
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inputs.terminate result
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lift :: forall m t i a. Monad m => m a -> ConsumeM m t i i a
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lift computation = ConsumeM \inputs -> do
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lift :: forall m i a. Monad m => m a -> ConsumeM m i i a
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lift computation = ConsumeM \producer -> do
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result <- computation
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inputs.continue inputs.producer result
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pure (result /\ producer)
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producer :: forall m t i. Monad m => ConsumeM m t i i (Producer m i)
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producer = ConsumeM \inputs -> inputs.continue inputs.producer inputs.producer
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producer :: forall m i. Monad m => ConsumeM m i i (Producer m i)
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producer = ConsumeM \p -> pure (p /\ p)
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mapSource :: forall m t i o. Monad m => (Producer m i -> Producer m o) -> ConsumeM m t i o Unit
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mapSource f = ConsumeM \inputs -> do
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let new = f inputs.producer
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inputs.continue new unit
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mapSource :: forall m i o. Monad m => (Producer m i -> Producer m o) -> ConsumeM m i o Unit
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mapSource f = ConsumeM \producer -> do
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pure (unit /\ f producer)
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runConsumeM :: forall m i t. Monad m => Producer m i -> Finished m t i -> m t
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runConsumeM producer (ConsumeM run) = run
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{ producer
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, terminate: pure
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, continue: \producer value -> absurd value -- not eta-reduced for clarity
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}
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runConsumeM :: forall m i o a. Monad m => Producer m i -> ConsumeM m i o a -> m a
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runConsumeM producer (ConsumeM run) = do
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result /\ producer' <- run producer
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destroyProducer producer'
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pure result
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runConsumeM_ :: forall m t. Monad m => Finished m t Unit -> m t
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runConsumeM_ :: forall m a o. Monad m => ConsumeM m Unit o a -> m a
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runConsumeM_ = runConsumeM unitProducer
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---------- Typeclass instances
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instance Monad m => Functor (Producer m) where
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map f (Producer producer) = Producer case _ of
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Destroy c -> producer (Destroy c)
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Produce next -> producer $ Produce \a p -> next (f a) (map f p)
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instance Monad m => IxFunctor (ConsumeM m t) where
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imap f (ConsumeM consumer) = ConsumeM
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\inputs -> consumer
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{ producer: inputs.producer
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, terminate: inputs.terminate
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, continue: \producer a -> inputs.continue producer (f a)
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instance Functor m => Functor (Producer m) where
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map f (Producer producer) = Producer
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{ destroy: producer.destroy
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, produce: producer.produce <#> map (bimap f (map f))
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}
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instance Monad m => IxApply (ConsumeM m t) where
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instance Functor m => IxFunctor (ConsumeM m) where
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imap f (ConsumeM consumer) = ConsumeM
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\producer -> consumer producer <#> first f
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instance Functor m => Functor (ConsumeM m i i) where
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map = imap
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instance Monad m => IxApply (ConsumeM m) where
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iapply = iap
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instance Monad m => IxApplicative (ConsumeM m t) where
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ipure a = ConsumeM \inputs -> inputs.continue inputs.producer a
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instance Monad m => Apply (ConsumeM m i i) where
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apply = iapply
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instance Monad m => IxBind (ConsumeM m t) where
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instance Monad m => IxApplicative (ConsumeM m) where
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ipure a = ConsumeM \p -> pure (a /\ p)
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instance Monad m => Applicative (ConsumeM m i i) where
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pure = ipure
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instance Monad m => IxBind (ConsumeM m) where
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ibind (ConsumeM consumer) f = ConsumeM
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\inputs -> do
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consumerResult <- consumer
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{ producer: inputs.producer
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, terminate: \result -> pure (Left result)
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, continue: \a b -> pure (Right (a /\ b))
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}
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case consumerResult of
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-- Terminated
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Left final -> inputs.terminate final
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-- Kept going
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Right (producer' /\ result) -> do
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\producer -> do
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result /\ producer' <- consumer producer
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let (ConsumeM consumer') = f result
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consumer' producer'
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consumer'
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{ producer: producer'
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, continue: inputs.continue
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, terminate: inputs.terminate
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}
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instance Monad m => Bind (ConsumeM m i i) where
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bind = ibind
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instance Monad m => IxMonad (ConsumeM m t)
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instance Monad m => IxMonad (ConsumeM m)
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instance Monad m => Monad (ConsumeM m i i)
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---------- Merge producers
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type AffProducer = Producer Aff
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instance Alt AffProducer where
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alt first second = Producer case _ of
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Produce continue -> ado
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alt first second = Producer
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{ destroy:
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parSequence_
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[ destroyProducer first
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, destroyProducer second
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]
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, produce: ado
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result <- parOneOf
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[ produce first <#> Left
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, produce second <#> Right
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]
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in
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case result of
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Left (result /\ first') -> continue result (first' <|> second)
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Right (result /\ second') -> continue result (first <|> second')
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Destroy continue -> ado
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parSequence_
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[ destroyProducer first
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, destroyProducer second
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]
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in continue
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pure case result of
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Left (result /\ first') -> result /\ (first' <|> second)
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Right (result /\ second') -> result /\ (first <|> second')
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}
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instance Plus AffProducer where
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empty = Producer \_ -> never
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empty = Producer { destroy: pure unit, produce: never }
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