Control.Monad.IO.Unwrappable

Contains a class and instance for MonadIO implementations that can be run directly in MonadIO and | then reconstructed to the original type, without changing the overall semantics.

Documentation

class MonadIO m => MonadIOUnwrappable m where

Represents a MonadIO where any change further up the monad stack can be | represented lower down in the stack.

Associated Types

type MonadIOWrapType m :: * -> *

type MonadIOStateType m :: *

Methods

unwrapState :: m (MonadIOStateType m)

Sets up state (e.g. an IORef) to be used to simulate the monad from the | IO monad.

unwrapMonadIO :: MonadIOStateType m -> m a -> IO (MonadIOWrapType m a)

Maps the monad to only use IO level constructs and the state set up | using unwrapState.

rewrapMonadIO :: MonadIOStateType m -> MonadIOWrapType m a -> m a

Reverses a previous unwrapMonadIO operation.

Instances

MonadIOUnwrappable IO

(Error e, MonadIO m, MonadIOUnwrappable m) => MonadIOUnwrappable (ErrorT e m)

(MonadIO m, MonadIOUnwrappable m) => MonadIOUnwrappable (ReaderT r m)

(MonadIO m, MonadIOUnwrappable m) => MonadIOUnwrappable (StateT r m)