Safe Haskell	None
Language	Haskell2010

Control.Effects.Signal

Synopsis

Documentation

class MonadEffect (Signal a b) m => MonadEffectSignal a b m where Source #

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 Source #

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

Instances

MonadEffect (Signal a b) IO => MonadEffectSignal a b IO Source #
Methods signal :: a -> IO b Source #
(MonadEffectSignal a b m, MonadTrans t, Monad (t m)) => MonadEffectSignal a b (t m) Source #
Methods signal :: a -> t m b Source #
Monad m => MonadEffectSignal a b (MaybeT m) Source #
Methods signal :: a -> MaybeT m b Source #
Monad m => MonadEffectSignal e b (ExceptT e m) Source #
Methods signal :: e -> ExceptT e m b Source #

data ResumeOrBreak b c Source #

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 :: Throws a m => a -> m b Source #

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 Source #

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.

type Throws e m = MonadEffectSignal e Void m Source #

handleException :: Monad m => (a -> m c) -> ExceptT a m c -> m c Source #

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

handleToEither :: ExceptT e m a -> m (Either e a) Source #

See documentation for handleException. This handler gives you an Either.

module Control.Effects

module Control.Monad.Trans.Except

newtype MaybeT m a :: (* -> *) -> * -> * #

The parameterizable maybe monad, obtained by composing an arbitrary monad with the Maybe monad.

Computations are actions that may produce a value or exit.

The return function yields a computation that produces that value, while >>= sequences two subcomputations, exiting if either computation does.

Constructors

MaybeT
Fields runMaybeT :: m (Maybe a)

Instances

MonadTransControl MaybeT
Associated Types type StT (MaybeT :: (* -> ) -> -> ) a :: # Methods liftWith :: Monad m => (Run MaybeT -> m a) -> MaybeT m a # restoreT :: Monad m => m (StT MaybeT a) -> MaybeT m a #
MonadTrans MaybeT
Methods lift :: Monad m => m a -> MaybeT m a #
Monad m => MonadEffectSignal a b (MaybeT m) Source #
Methods signal :: a -> MaybeT m b Source #
MonadState s m => MonadState s (MaybeT m)
Methods get :: MaybeT m s # put :: s -> MaybeT m () # state :: (s -> (a, s)) -> MaybeT m a #
MonadReader r m => MonadReader r (MaybeT m)
Methods ask :: MaybeT m r # local :: (r -> r) -> MaybeT m a -> MaybeT m a # reader :: (r -> a) -> MaybeT m a #
MonadBaseControl b m => MonadBaseControl b (MaybeT m)
Associated Types type StM (MaybeT m :: * -> ) a :: # Methods liftBaseWith :: (RunInBase (MaybeT m) b -> b a) -> MaybeT m a # restoreM :: StM (MaybeT m) a -> MaybeT m a #
MonadBase b m => MonadBase b (MaybeT m)
Methods liftBase :: b α -> MaybeT m α #
Monad m => Monad (MaybeT m)
Methods (>>=) :: MaybeT m a -> (a -> MaybeT m b) -> MaybeT m b # (>>) :: MaybeT m a -> MaybeT m b -> MaybeT m b # return :: a -> MaybeT m a # fail :: String -> MaybeT m a #
Functor m => Functor (MaybeT m)
Methods fmap :: (a -> b) -> MaybeT m a -> MaybeT m b # (<$) :: a -> MaybeT m b -> MaybeT m a #
MonadFix m => MonadFix (MaybeT m)
Methods mfix :: (a -> MaybeT m a) -> MaybeT m a #
Monad m => MonadFail (MaybeT m)
Methods fail :: String -> MaybeT m a #
(Functor m, Monad m) => Applicative (MaybeT m)
Methods pure :: a -> MaybeT m a # (<>) :: MaybeT m (a -> b) -> MaybeT m a -> MaybeT m b # (>) :: MaybeT m a -> MaybeT m b -> MaybeT m b # (<*) :: MaybeT m a -> MaybeT m b -> MaybeT m a #
Foldable f => Foldable (MaybeT f)
Methods fold :: Monoid m => MaybeT f m -> m # foldMap :: Monoid m => (a -> m) -> MaybeT f a -> m # foldr :: (a -> b -> b) -> b -> MaybeT f a -> b # foldr' :: (a -> b -> b) -> b -> MaybeT f a -> b # foldl :: (b -> a -> b) -> b -> MaybeT f a -> b # foldl' :: (b -> a -> b) -> b -> MaybeT f a -> b # foldr1 :: (a -> a -> a) -> MaybeT f a -> a # foldl1 :: (a -> a -> a) -> MaybeT f a -> a # toList :: MaybeT f a -> [a] # null :: MaybeT f a -> Bool # length :: MaybeT f a -> Int # elem :: Eq a => a -> MaybeT f a -> Bool # maximum :: Ord a => MaybeT f a -> a # minimum :: Ord a => MaybeT f a -> a # sum :: Num a => MaybeT f a -> a # product :: Num a => MaybeT f a -> a #
Traversable f => Traversable (MaybeT f)
Methods traverse :: Applicative f => (a -> f b) -> MaybeT f a -> f (MaybeT f b) # sequenceA :: Applicative f => MaybeT f (f a) -> f (MaybeT f a) # mapM :: Monad m => (a -> m b) -> MaybeT f a -> m (MaybeT f b) # sequence :: Monad m => MaybeT f (m a) -> m (MaybeT f a) #
Contravariant m => Contravariant (MaybeT m)
Methods contramap :: (a -> b) -> MaybeT m b -> MaybeT m a # (>$) :: b -> MaybeT m b -> MaybeT m a #
(Functor m, Monad m) => Alternative (MaybeT m)
Methods empty :: MaybeT m a # (<\|>) :: MaybeT m a -> MaybeT m a -> MaybeT m a # some :: MaybeT m a -> MaybeT m [a] # many :: MaybeT m a -> MaybeT m [a] #
Monad m => MonadPlus (MaybeT m)
Methods mzero :: MaybeT m a # mplus :: MaybeT m a -> MaybeT m a -> MaybeT m a #
Eq1 m => Eq1 (MaybeT m)
Methods liftEq :: (a -> b -> Bool) -> MaybeT m a -> MaybeT m b -> Bool #
Ord1 m => Ord1 (MaybeT m)
Methods liftCompare :: (a -> b -> Ordering) -> MaybeT m a -> MaybeT m b -> Ordering #
Read1 m => Read1 (MaybeT m)
Methods liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (MaybeT m a) # liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [MaybeT m a] #
Show1 m => Show1 (MaybeT m)
Methods liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> MaybeT m a -> ShowS # liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [MaybeT m a] -> ShowS #
MonadZip m => MonadZip (MaybeT m)
Methods mzip :: MaybeT m a -> MaybeT m b -> MaybeT m (a, b) # mzipWith :: (a -> b -> c) -> MaybeT m a -> MaybeT m b -> MaybeT m c # munzip :: MaybeT m (a, b) -> (MaybeT m a, MaybeT m b) #
MonadIO m => MonadIO (MaybeT m)
Methods liftIO :: IO a -> MaybeT m a #
MonadThrow m => MonadThrow (MaybeT m)	Throws exceptions into the base monad.
Methods throwM :: Exception e => e -> MaybeT m a #
MonadCatch m => MonadCatch (MaybeT m)	Catches exceptions from the base monad.
Methods catch :: Exception e => MaybeT m a -> (e -> MaybeT m a) -> MaybeT m a #
PrimMonad m => PrimMonad (MaybeT m)
Associated Types type PrimState (MaybeT m :: * -> ) :: # Methods primitive :: (State# (PrimState (MaybeT m)) -> (#VoidRep, PtrRepLifted, State# (PrimState (MaybeT m)), a#)) -> MaybeT m a #
Zoom m n s t => Zoom (MaybeT m) (MaybeT n) s t
Methods zoom :: LensLike' (Zoomed (MaybeT m) c) t s -> MaybeT m c -> MaybeT n c #
(Eq1 m, Eq a) => Eq (MaybeT m a)
Methods (==) :: MaybeT m a -> MaybeT m a -> Bool # (/=) :: MaybeT m a -> MaybeT m a -> Bool #
(Ord1 m, Ord a) => Ord (MaybeT m a)
Methods compare :: MaybeT m a -> MaybeT m a -> Ordering # (<) :: MaybeT m a -> MaybeT m a -> Bool # (<=) :: MaybeT m a -> MaybeT m a -> Bool # (>) :: MaybeT m a -> MaybeT m a -> Bool # (>=) :: MaybeT m a -> MaybeT m a -> Bool # max :: MaybeT m a -> MaybeT m a -> MaybeT m a # min :: MaybeT m a -> MaybeT m a -> MaybeT m a #
(Read1 m, Read a) => Read (MaybeT m a)
Methods readsPrec :: Int -> ReadS (MaybeT m a) # readList :: ReadS [MaybeT m a] # readPrec :: ReadPrec (MaybeT m a) # readListPrec :: ReadPrec [MaybeT m a] #
(Show1 m, Show a) => Show (MaybeT m a)
Methods showsPrec :: Int -> MaybeT m a -> ShowS # show :: MaybeT m a -> String # showList :: [MaybeT m a] -> ShowS #
Wrapped (MaybeT m a)
Associated Types type Unwrapped (MaybeT m a) :: * # Methods _Wrapped' :: Iso' (MaybeT m a) (Unwrapped (MaybeT m a)) #
(~) * t (MaybeT n b) => Rewrapped (MaybeT m a) t

type StT MaybeT a
type StT MaybeT a = Maybe a
type Zoomed (MaybeT m)
type Zoomed (MaybeT m) = FocusingMay (Zoomed m)
type PrimState (MaybeT m)
type PrimState (MaybeT m) = PrimState m
type StM (MaybeT m) a
type StM (MaybeT m) a = ComposeSt MaybeT m a
type Unwrapped (MaybeT m a)
type Unwrapped (MaybeT m a) = m (Maybe a)

discardAllExceptions :: MaybeT m a -> m (Maybe a) Source #

Discard all the Throws and MonadEffectSignal constraints. If any exception was thrown the result will be Nothing.

showAllExceptions :: Functor m => ExceptT SomeSignal m a -> m (Either Text a) Source #

Satisfies all the Throws and MonadEffectSignal constraints _if_ they all throw Showable exceptions. The first thrown exception will be shown and returned as a Left result.