Control.Monad.Coroutine.SuspensionFunctors

This module defines some common suspension functors for use with the Control.Monad.Coroutine module.

Suspension functors

data Yield x y

The Yield functor instance is equivalent to (,) but more descriptive. A coroutine with this suspension functor provides a value with every suspension.

Constructors

Yield x y

Instances

Functor (Yield x)

newtype Await x y

The Await functor instance is equivalent to (->) but more descriptive. A coroutine with this suspension functor demands a value whenever it suspends, before it can resume its execution.

Constructors

Await (x -> y)

Instances

Functor (Await x)

data Request request response x

The Request functor instance combines a Yield of a request with an Await for a response.

Constructors

Request request (response -> x)

Instances

Functor (Request x f)

data ReadRequest x z

Combines a Yield of a Reader with an Await for a ReadingResult.

Instances

Functor (ReadRequest x)

data ReadingResult x py y

Constructors

ResultPart py (Reader x py y)

A part of the result with the reader of more input

FinalResult y

Final result chunk

type Reader x py y = x -> Reading x py y

data Reading x py y

Constructors

Final x y

Final result chunk with the unconsumed portion of the input

Advance (Reader x py y) y py

A part of the result with the reader of more input and the EOF

Deferred (Reader x py y) y

Reader of more input, plus the result if there isn't any.

eitherFunctor :: (l x -> y) -> (r x -> y) -> Sum l r x -> y

Like either for the Sum data type.

yield :: Monad m => x -> Coroutine (Yield x) m ()

Suspend the current coroutine yielding a value.

await :: Monad m => Coroutine (Await x) m x

Suspend the current coroutine until a value is provided.

request :: Monad m => x -> Coroutine (Request x y) m y

Suspend yielding a request and awaiting the response.

requestRead :: (Monad m, Monoid x) => Reader x py y -> Coroutine (ReadRequest x) m (ReadingResult x py y)

Suspend yielding a ReadRequest and awaiting the ReadingResult.

Utility functions

concatYields :: (Monad m, Foldable f) => Coroutine (Yield (f x)) m r -> Coroutine (Yield x) m r

Converts a coroutine yielding collections of values into one yielding single values.

concatAwaits :: (Monad m, Foldable f) => Coroutine (Await x) m r -> Coroutine (Await (f x)) m r

Converts a coroutine awaiting single values into one awaiting collections of values.

WeaveSteppers for weaving pairs of coroutines

weaveAwaitYield :: Monad m => x -> WeaveStepper (Await x) (Yield x) Identity m r1 r2 (r1, r2)

Weaves the suspensions of a Yield and an Await coroutine together into a plain Identity coroutine. If the Yield coroutine terminates first, the Await one is resumed using the argument default value.

weaveAwaitMaybeYield :: Monad m => WeaveStepper (Await (Maybe x)) (Yield x) Identity m r1 r2 (r1, r2)

Like weaveAwaitYield, except the Await coroutine expects Maybe-wrapped values. After the Yield coroutine terminates, the Await coroutine receives only Nothing.

weaveRequests :: Monad m => x -> y -> WeaveStepper (Request x y) (Request y x) (Yield (x, y)) m r1 r2 (r1, r2)

Weaves two complementary Request coroutine suspensions into a coroutine yielding both requests. If one coroutine terminates before the other, the remaining coroutine is fed the appropriate default value argument.

weaveReadWriteRequests :: (Monad m, Monoid x) => WeaveStepper (ReadRequest x) (Request x x) Identity m r1 r2 (r1, r2)

The consumer coroutine requests input through ReadRequest and gets ReadingResult in response. The producer coroutine receives the unconsumed portion of its last requested chunk as response.

weaveNestedReadWriteRequests :: (Monad m, Functor s, Monoid x) => NestWeaveStepper s (ReadRequest x) (Request x x) m r1 r2 (r1, r2)

Like weaveReadWriteRequests but for nested coroutines.