Control.Monad.Resumable

A monad transformer for resumable exceptions. The ResumableT transformer is isomorphic to ReactT, the dominant reactivity monad in the literature. The differences serve to match the mtl style.

Monadic interface

class Monad m => MonadResumable req res m | m -> req res where

A monadic interface for resumable exceptions.

Methods

yield :: req -> (res -> m a) -> m a

Raise the exception: a request and a resumption to use if the request can be handled.

handle :: m a -> (req -> (res -> m a) -> m a) -> m a

Installs a handler to quiesce an exception before it percolates to the higher-level handlers.

Instances

MonadResumable req res m => MonadResumable req res (ContT r m)

(Error e, MonadResumable req res m) => MonadResumable req res (ErrorT e m)

MonadResumable req res m => MonadResumable req res (StateT s m)

(Monoid w, MonadResumable req res m) => MonadResumable req res (WriterT w m)

MonadResumable req res m => MonadResumable req res (ReaderT r m)

(Monoid w, MonadResumable req res m) => MonadResumable req res (RWST r w s m)

Monad m => MonadResumable req res (ResumableT Dynamic req res m)

Monad m => MonadResumable req res (ResumableT Static req res m)

signal :: MonadResumable req res m => req -> m res

Variation on yield that immediately returns the result.

respond :: MonadResumable req res m => (req -> m res) -> m a -> m a

Variation on handle that always applies the resumption.

Monad transformer

type Resumable scope req res = ResumableT scope req res Identity

newtype ResumableT scope req res m a

Constructors

ResumableT

Fields

unResumableT :: m (Either (req, res -> ResumableT scope req res m a) a)

Instances

(Monoid w, MonadReader r m, MonadState s m, MonadWriter w m) => MonadRWS r w s (ResumableT Dynamic req res m)

(Monoid w, MonadReader r m, MonadState s m, MonadWriter w m) => MonadRWS r w s (ResumableT Static req res m)

Monad m => MonadResumable req res (ResumableT Dynamic req res m)

Monad m => MonadResumable req res (ResumableT Static req res m)

MonadReader r m => MonadReader r (ResumableT Dynamic req res m)

MonadReader r m => MonadReader r (ResumableT Static req res m)

MonadState s m => MonadState s (ResumableT scope req res m)

MonadError e m => MonadError e (ResumableT Dynamic req res m)

MonadError e m => MonadError e (ResumableT Static req res m)

MonadWriter w m => MonadWriter w (ResumableT scope req res m)

Scoped scope (ResumableT scope' req res m)

MonadTrans (ResumableT scope req res)

Monad m => Monad (ResumableT scope req res m)

Functor m => Functor (ResumableT scope req res m)

MonadFix m => MonadFix (ResumableT scope req res m)

MonadCont m => MonadCont (ResumableT scope req res m)

MonadIO m => MonadIO (ResumableT scope req res m)

Run functions

runResumableT :: Monad m => ResumableT scope req res m a -> m (req -> (res -> ResumableT scope req res m a) -> ResumableT scope req res m a) -> m a

The preferred top-level interface nevers allows exceptions to go unhandled.

runResumableT_responder :: Monad m => ResumableT scope req res m a -> m (req -> ResumableT scope req res m res) -> m a

This variation recognizes that the handling of requests primarily involves generating responses.

runResumableT' :: Monad m => ResumableT scope req res m a -> (req -> (res -> ResumableT scope req res m a) -> ResumableT scope req res m a) -> m a

The handler does not depend on the inner monad.

runResumableT_responder' :: Monad m => ResumableT scope req res m a -> (req -> ResumableT scope req res m res) -> m a

The responder does not depend on the inner monad.

Scope manipulation

data Static

Instances

(Monoid w, MonadReader r m, MonadState s m, MonadWriter w m) => MonadRWS r w s (ResumableT Static req res m)

Monad m => MonadResumable req res (ResumableT Static req res m)

MonadReader r m => MonadReader r (ResumableT Static req res m)

MonadError e m => MonadError e (ResumableT Static req res m)

data Dynamic

Instances

(Monoid w, MonadReader r m, MonadState s m, MonadWriter w m) => MonadRWS r w s (ResumableT Dynamic req res m)

Monad m => MonadResumable req res (ResumableT Dynamic req res m)

MonadReader r m => MonadReader r (ResumableT Dynamic req res m)

MonadError e m => MonadError e (ResumableT Dynamic req res m)

asStatic :: ResumableT Static req res m a -> ResumableT Static req res m a

Establishes static scoping as default.

asDynamic :: ResumableT Dynamic req res m a -> ResumableT Dynamic req res m a

Establishes dynamic scoping as default.

statically :: Scoped Static m => (ScopedAs Static m a -> ScopedAs Static m b) -> m a -> m b

dynamically :: Scoped Dynamic m => (ScopedAs Dynamic m a -> ScopedAs Dynamic m b) -> m a -> m b

Manipulating the inner monad

mapResumableT_static :: (m (Either (req, res -> ResumableT scope req res m a) a) -> n (Either (req', res' -> ResumableT scope' req' res' n b) b)) -> ResumableT scope req res m a -> ResumableT scope' req' res' n b

This manipulation of the inner monad acheives static scoping -- the manipulation is not preserved in the resumption.

mapResumableT_dynamic :: (Monad m, Monad n) => (m (Either (req, res -> ResumableT scope req res m a) a) -> n (Either (req, res -> ResumableT scope req res m a) b)) -> ResumableT scope req res m a -> ResumableT scope req res n b

This manipulation of the inner monad acheives dynamic scoping -- the manipulation is preserved in the resumption.