Control.Monad.Trans.Lift.Catch

Lifting the catch operation.

Documentation

class MonadTrans t => LiftCatch t where

The class of monad transformers capable of lifting catch.

Methods

liftCatch :: Monad m => Catch e m (StT t a) -> Catch e (t m) a

Lift the catch operation. Should satisfy the uniformity property

• lift (cf m f) = liftCatch (lift . cf) (lift f)

Instances

LiftCatch MaybeT

LiftCatch ListT

LiftCatch IdentityT

Monoid w => LiftCatch (WriterT w)

Monoid w => LiftCatch (WriterT w)

LiftCatch (ExceptT e)

LiftCatch (StateT s)

LiftCatch (StateT s)

LiftCatch (ReaderT r)

Monoid w => LiftCatch (RWST r w s)

Monoid w => LiftCatch (RWST r w s)

type Catch e m a = m a -> (e -> m a) -> m a

Signature of the catchE operation, introduced in Control.Monad.Trans.Except. Any lifting function liftCatch should satisfy

• lift (cf m f) = liftCatch (lift . cf) (lift f)

defaultLiftCatch

Arguments

:: (Monad m, LiftCatch n)

=> (forall x. n m x -> t m x)

Monad constructor

-> (forall o x. t o x -> n o x)

Monad deconstructor

-> Catch e m (StT n a)

-> Catch e (t m) a

Default definition for the liftCatch method.

module Control.Monad.Trans.Class