Safe Haskell	Safe
Language	Haskell2010

Control.Monad.Trans.Interruptible

Contents

Instance accessors
Resumers for stacks of interruptibles
Interruptible applications

Synopsis

Documentation

class MonadTrans t => Interruptible t where Source #

Interruptible monad transformers.

A monad transformer can be made interruptible if it returns its final context from its type creator, and if it is possible to hoist this context again into the monad at the begining of its execution.

For example, StateT can be interrupted because runStateT returns its final state, and because its state can be set again at creation simply by passing it as an parameter to runStateT. An Error context can not be hoisted back at the transformer, thus Error can not be interrupted.

When instantiating, do not forget to create the corresponding inCtx and peelCtx functions, for documenting the RSt format and keeping the class consistent.

Minimal complete definition

resume

Associated Types

type RSt t a :: * Source #

Context data of the transformer

Methods

resume :: Monad m => (a -> t m b) -> RSt t a -> m (RSt t b) Source #

Resumes the execution of an interruptible transformer

Instances

Interruptible (EitherT e) Source #
Associated Types type RSt (EitherT e :: (* -> ) -> -> ) a :: Source # Methods resume :: Monad m => (a -> EitherT e m b) -> RSt (EitherT e) a -> m (RSt (EitherT e) b) Source #
Interruptible (StateT st) Source #
Associated Types type RSt (StateT st :: (* -> ) -> -> ) a :: Source # Methods resume :: Monad m => (a -> StateT st m b) -> RSt (StateT st) a -> m (RSt (StateT st) b) Source #
Monoid w => Interruptible (WriterT w) Source #
Associated Types type RSt (WriterT w :: (* -> ) -> -> ) a :: Source # Methods resume :: Monad m => (a -> WriterT w m b) -> RSt (WriterT w) a -> m (RSt (WriterT w) b) Source #
Interruptible (ReaderT * r) Source #
Associated Types type RSt (ReaderT * r :: (* -> ) -> -> ) a :: Source # Methods resume :: Monad m => (a -> ReaderT * r m b) -> RSt (ReaderT * r) a -> m (RSt (ReaderT * r) b) Source #
Monoid w => Interruptible (RWST r w s) Source #
Associated Types type RSt (RWST r w s :: (* -> ) -> -> ) a :: Source # Methods resume :: Monad m => (a -> RWST r w s m b) -> RSt (RWST r w s) a -> m (RSt (RWST r w s) b) Source #

Instance accessors

inEitherTCtx :: a -> RSt (EitherT e) a Source #

Cretes an interrupted EitherT context

peelEitherTCtx :: RSt (EitherT e) a -> Either e a Source #

Unwraps an interrupted EitherT context

inStateTCtx :: st -> a -> RSt (StateT st) a Source #

Creates an interrupted StateT context

peelStateTCtx :: RSt (StateT st) a -> (a, st) Source #

Unwraps an interrupted StateT context

inWriterTCtx :: Monoid w => a -> RSt (WriterT w) a Source #

Creates an interrupted WriterT context

peelWriterTCtx :: RSt (WriterT w) a -> (a, w) Source #

Unwraps an interrupted WriterT context

inReaderTCtx :: r -> a -> RSt (ReaderT r) a Source #

Creates an interrupted ReaderT context

peelReaderTCtx :: RSt (ReaderT r) a -> a Source #

Unwraps an interrupted WriterT context

inRWSTCtx :: Monoid w => r -> s -> a -> RSt (RWST r w s) a Source #

Creates an interrupted RWST context

peelRWSTCtx :: RSt (RWST r w s) a -> (a, w, s) Source #

Unwraps an interrupted RWST context

Resumers for stacks of interruptibles

resume2 :: (Monad m, Interruptible t, Monad (t m), Interruptible u) => (a -> u (t m) b) -> RSt t (RSt u a) -> m (RSt t (RSt u b)) Source #

resume3 :: (Monad m, Interruptible t0, Monad (t0 m), Interruptible t1, Monad (t1 (t0 m)), Interruptible t2) => (a -> t2 (t1 (t0 m)) b) -> RSt t0 (RSt t1 (RSt t2 a)) -> m (RSt t0 (RSt t1 (RSt t2 b))) Source #

resume4 :: (Monad m, Interruptible t0, Interruptible t1, Interruptible t2, Interruptible t3, Monad (t0 m), Monad (t1 (t0 m)), Monad (t2 (t1 (t0 m)))) => (a -> t3 (t2 (t1 (t0 m))) b) -> RSt t0 (RSt t1 (RSt t2 (RSt t3 a))) -> m (RSt t0 (RSt t1 (RSt t2 (RSt t3 b)))) Source #

resume5 :: (Monad m, Interruptible t0, Interruptible t1, Interruptible t2, Interruptible t3, Interruptible t4, Monad (t0 m), Monad (t1 (t0 m)), Monad (t2 (t1 (t0 m))), Monad (t3 (t2 (t1 (t0 m))))) => (a -> t4 (t3 (t2 (t1 (t0 m)))) b) -> RSt t0 (RSt t1 (RSt t2 (RSt t3 (RSt t4 a)))) -> m (RSt t0 (RSt t1 (RSt t2 (RSt t3 (RSt t4 b))))) Source #

Interruptible applications

intercalateWith :: Monad m => ((a -> t a) -> rsta -> m rsta) -> (b -> a -> t a) -> [b] -> [rsta] -> m [rsta] Source #

Folds the second list with the function applied to the first, intercalating the evaluation. That is:

intercalateWith resume f [a00, a10, a20] [b1, b2] = do
  a01 <- resume (f b1) a00
  a11 <- resume (f b1) a10
  a21 <- resume (f b1) a20
  a02 <- resume (f b2) a11
  a12 <- resume (f b2) a21
  a22 <- resume (f b2) a31
  return [a02, a12, a22]

Usefull for consuming lazy sequences.

The resume function is parametric for allowing resuming deeper Interruptible chains, with resume2, resume3, etc.