Control.Failure

Type classes for returning failures.

Type class

class Monad f => Failure e f where

Methods

failure :: e -> f v

Instances

Exception e => Failure e IO

Failure e []

Failure e Maybe

(MonadTrans t, Failure e m, Monad (t m)) => Failure e (t m)

Instance for all monad transformers, simply lift the failure into the base monad.

Failure e (Either e)

Wrapping failures

class Failure e f => WrapFailure e f where

Methods

wrapFailure :: (forall eIn. Exception eIn => eIn -> e) -> f a -> f a

Wrap the failure value, if any, with the given function. This is useful in particular when you want all the exceptions returned from a certain library to be of a certain type, even if they were generated by a different library.

Instances

Exception e => WrapFailure e IO

Convenience String failure

newtype StringException

Constructors

StringException String

Instances

Show StringException

Typeable StringException

Exception StringException

failureString :: Failure StringException m => String -> m a

Call failure with a String.

Convert Failures into concrete types

class Try f where

Associated Types

type Error f

Methods

try :: Failure (Error f) f' => f a -> f' a

Instances

Try []

Try Maybe

Try (Either e)

data NothingException

Constructors

NothingException

Instances

Show NothingException

Typeable NothingException

Exception NothingException

data NullException

Constructors

NullException

Instances

Show NullException

Typeable NullException

Exception NullException