Control.Effect.Fail

Documentation

newtype Fail (m :: * -> *) k

Constructors

Fail String

Instances

Effect Fail

Defined in Control.Effect.Fail

Methods

handle :: Functor f => f () -> (forall x. f (m x) -> n (f x)) -> Fail m (m a) -> Fail n (n (f a))

HFunctor Fail

Defined in Control.Effect.Fail

Methods

fmap' :: (a -> b) -> Fail m a -> Fail m b

hmap :: (forall x. m x -> n x) -> Fail m a -> Fail n a

Functor (Fail m)

Defined in Control.Effect.Fail

Methods

fmap :: (a -> b) -> Fail m a -> Fail m b

(<$) :: a -> Fail m b -> Fail m a

(Carrier sig m, Effect sig) => Carrier (Fail :+: sig) (FailC m)

Defined in Control.Effect.Fail

Methods

eff :: (Fail :+: sig) (FailC m) (FailC m a) -> FailC m a

class Monad m => MonadFail (m :: Type -> Type) where

When a value is bound in do-notation, the pattern on the left hand side of <- might not match. In this case, this class provides a function to recover.

A Monad without a MonadFail instance may only be used in conjunction with pattern that always match, such as newtypes, tuples, data types with only a single data constructor, and irrefutable patterns (~pat).

Instances of MonadFail should satisfy the following law: fail s should be a left zero for >>=,

fail s >>= f  =  fail s

If your Monad is also MonadPlus, a popular definition is

fail _ = mzero

Since: base-4.9.0.0

Methods

fail :: String -> m a

Instances

MonadFail []

Since: base-4.9.0.0

Defined in Control.Monad.Fail

Methods

fail :: String -> [a]

MonadFail Maybe

Since: base-4.9.0.0

Defined in Control.Monad.Fail

Methods

fail :: String -> Maybe a

MonadFail IO

Since: base-4.9.0.0

Defined in Control.Monad.Fail

Methods

fail :: String -> IO a

MonadFail ReadP

Since: base-4.9.0.0

Defined in Text.ParserCombinators.ReadP

Methods

fail :: String -> ReadP a

MonadFail P

Since: base-4.9.0.0

Defined in Text.ParserCombinators.ReadP

Methods

fail :: String -> P a

MonadFail m => MonadFail (ResourceC m)

Defined in Control.Effect.Resource

Methods

fail :: String -> ResourceC m a

MonadFail m => MonadFail (NonDetC m)

Defined in Control.Effect.NonDet

Methods

fail :: String -> NonDetC m a

MonadFail m => MonadFail (LiftC m)

Defined in Control.Effect.Lift

Methods

fail :: String -> LiftC m a

MonadFail m => MonadFail (FreshC m)

Defined in Control.Effect.Fresh

Methods

fail :: String -> FreshC m a

(Carrier sig m, Effect sig) => MonadFail (FailC m)

Defined in Control.Effect.Fail

Methods

fail :: String -> FailC m a

MonadFail m => MonadFail (CutC m)

Defined in Control.Effect.Cut

Methods

fail :: String -> CutC m a

MonadFail m => MonadFail (OnceC m)

Defined in Control.Effect.Cull

Methods

fail :: String -> OnceC m a

MonadFail m => MonadFail (CullC m)

Defined in Control.Effect.Cull

Methods

fail :: String -> CullC m a

MonadFail m => MonadFail (TraceByReturningC m)

Defined in Control.Effect.Trace

Methods

fail :: String -> TraceByReturningC m a

MonadFail m => MonadFail (TraceByIgnoringC m)

Defined in Control.Effect.Trace

Methods

fail :: String -> TraceByIgnoringC m a

MonadFail m => MonadFail (TraceByPrintingC m)

Defined in Control.Effect.Trace

Methods

fail :: String -> TraceByPrintingC m a

MonadFail f => MonadFail (Ap f)

Since: base-4.12.0.0

Defined in Data.Monoid

Methods

fail :: String -> Ap f a

MonadFail m => MonadFail (IdentityT m)

Defined in Control.Monad.Trans.Identity

Methods

fail :: String -> IdentityT m a

(Monad m, Error e) => MonadFail (ErrorT e m)

Defined in Control.Monad.Trans.Error

Methods

fail :: String -> ErrorT e m a

MonadFail m => MonadFail (ReaderT r m)

Defined in Control.Monad.Trans.Reader

Methods

fail :: String -> ReaderT r m a

MonadFail m => MonadFail (StateC s m)

Defined in Control.Effect.State.Strict

Methods

fail :: String -> StateC s m a

MonadFail m => MonadFail (StateC s m)

Defined in Control.Effect.State.Lazy

Methods

fail :: String -> StateC s m a

MonadFail m => MonadFail (ReaderC r m)

Defined in Control.Effect.Reader

Methods

fail :: String -> ReaderC r m a

MonadFail m => MonadFail (RandomC g m)

Defined in Control.Effect.Random

Methods

fail :: String -> RandomC g m a

MonadFail m => MonadFail (InterpretC eff m)

Defined in Control.Effect.Interpret

Methods

fail :: String -> InterpretC eff m a

MonadFail m => MonadFail (ErrorC e m)

Defined in Control.Effect.Error

Methods

fail :: String -> ErrorC e m a

MonadFail m => MonadFail (ResumableWithC err m)

Defined in Control.Effect.Resumable

Methods

fail :: String -> ResumableWithC err m a

MonadFail m => MonadFail (ResumableC err m)

Defined in Control.Effect.Resumable

Methods

fail :: String -> ResumableC err m a

MonadFail m => MonadFail (WriterC w m)

Defined in Control.Effect.Writer

Methods

fail :: String -> WriterC w m a

MonadFail m => MonadFail (InterpretStateC eff s m)

Defined in Control.Effect.Interpret

Methods

fail :: String -> InterpretStateC eff s m a

runFail :: FailC m a -> m (Either String a)

Run a Fail effect, returning failure messages in Left and successful computations’ results in Right.

run (runFail (pure a)) == Right a

newtype FailC m a

Constructors

FailC

Fields

• runFailC :: ErrorC String m a

Instances

MonadTrans FailC

Defined in Control.Effect.Fail

Methods

lift :: Monad m => m a -> FailC m a

Monad m => Monad (FailC m)

Defined in Control.Effect.Fail

Methods

(>>=) :: FailC m a -> (a -> FailC m b) -> FailC m b

(>>) :: FailC m a -> FailC m b -> FailC m b

return :: a -> FailC m a

fail :: String -> FailC m a

Functor m => Functor (FailC m)

Defined in Control.Effect.Fail

Methods

fmap :: (a -> b) -> FailC m a -> FailC m b

(<$) :: a -> FailC m b -> FailC m a

(Carrier sig m, Effect sig) => MonadFail (FailC m)

Defined in Control.Effect.Fail

Methods

fail :: String -> FailC m a

Applicative m => Applicative (FailC m)

Defined in Control.Effect.Fail

Methods

pure :: a -> FailC m a

(<*>) :: FailC m (a -> b) -> FailC m a -> FailC m b

liftA2 :: (a -> b -> c) -> FailC m a -> FailC m b -> FailC m c

(*>) :: FailC m a -> FailC m b -> FailC m b

(<*) :: FailC m a -> FailC m b -> FailC m a

MonadIO m => MonadIO (FailC m)

Defined in Control.Effect.Fail

Methods

liftIO :: IO a -> FailC m a

Alternative m => Alternative (FailC m)

Defined in Control.Effect.Fail

Methods

empty :: FailC m a

(<|>) :: FailC m a -> FailC m a -> FailC m a

some :: FailC m a -> FailC m [a]

many :: FailC m a -> FailC m [a]

(Alternative m, Monad m) => MonadPlus (FailC m)

Defined in Control.Effect.Fail

Methods

mzero :: FailC m a

mplus :: FailC m a -> FailC m a -> FailC m a

(Carrier sig m, Effect sig) => Carrier (Fail :+: sig) (FailC m)

Defined in Control.Effect.Fail

Methods

eff :: (Fail :+: sig) (FailC m) (FailC m a) -> FailC m a