Control.Effects.Signal

Documentation

class MonadEffect (Signal a b) m => MonadEffectSignal a b m | m a -> b where

This class allows you to "throw" a signal. For the most part signals are the same as checked exceptions. The difference here is that the handler has the option to provide the value that will be the result _of calling the signal function_. This effectibvely allows you to have recoverable exceptions at the call site, instead of just at the handling site.

This class can be considered an alias for MonadEffect (Signal a b) so your code isn't required to provide any instances.

Methods

signal :: a -> m b

There are no restrictions on the type of values that can be thrown or returned.

Instances

(MonadEffectSignal a b m, MonadTrans t, Monad (t m)) => MonadEffectSignal a b (t m)

Methods

signal :: a -> t m b

data ResumeOrBreak b c

The handle function will return a value of this type.

Constructors

Resume b

Give a value to the caller of signal and keep going.

Break c

Continue the execution after the handler. The handler will return this value

throwSignal :: MonadEffectSignal a Void m => a -> m b

Throw a signal with no possible recovery. The handler is forced to only return the Break constructor because it cannot construct a Void value.

If this function is used along with handleAsException, this module behaves like regular checked exceptions.

handleSignal :: Monad m => (a -> m (ResumeOrBreak b c)) -> EffectHandler (Signal a b) (ExceptT c m) c -> m c

Handle signals of a computation. The handler function has the option to provide a value to the caller of signal and continue execution there, or do what regular exception handlers do and continue execution after the handler.

handleAsException :: Monad m => (a -> m c) -> EffectHandler (Signal a b) (ExceptT c m) c -> m c

This handler can only behave like a regular exception handler. If used along with throwSignal this module behaves like regular checked exceptions.

module Control.Effects