Control.Eff.Lift

Lifting primitive Monad types to effectful computations. We only allow a single Lifted Monad because Monads aren't commutative (e.g. Maybe (IO a) is functionally distinct from IO (Maybe a)).

Documentation

newtype Lift m a

Lifting: emulating monad transformers

Constructors

Lift (m a)

Instances

MonadBase m m => MonadBaseControl m (Eff (Lift m ': ([] :: [* -> *])))

Defined in Control.Eff.Internal

Associated Types

type StM (Eff (Lift m ': [])) a :: *

Methods

liftBaseWith :: (RunInBase (Eff (Lift m ': [])) m -> m a) -> Eff (Lift m ': []) a

restoreM :: StM (Eff (Lift m ': [])) a -> Eff (Lift m ': []) a

type StM (Eff (Lift m ': ([] :: [* -> *]))) a

Defined in Control.Eff.Internal

type StM (Eff (Lift m ': ([] :: [* -> *]))) a = a

type Lifted m r = SetMember Lift (Lift m) r

A convenient alias to 'SetMember Lift (Lift m) r'

type LiftedBase m r = (SetMember Lift (Lift m) r, MonadBaseControl m (Eff r))

Same as Lifted but with additional MonadBaseControl constraint

lift :: SetMember Lift (Lift m) r => m a -> Eff r a

embed an operation of type `m a` into the Eff monad when Lift m is in a part of the effect-list.

By using SetMember, it is possible to assert that the lifted type occurs only once in the effect list

runLift :: Monad m => Eff '[Lift m] w -> m w

The handler of Lift requests. It is meant to be terminal: we only allow a single Lifted Monad.

catchDynE :: forall e a r. (Lifted IO r, Exception e) => Eff r a -> (e -> Eff r a) -> Eff r a

Catching of dynamic exceptions See the problem in http://okmij.org/ftp/Haskell/misc.html#catch-MonadIO