Safe Haskell	Safe-Inferred
Language	Haskell2010

Text.XML.Light.Extractors.Internal.Result

Synopsis

data Result e a
- = Fatal e
- | Fail e
- | Ok a
toEither :: Result a b -> Either a b
escalate :: Result e a -> Result e a
data ResultT e m a
runResultT :: ResultT e m a -> m (Result e a)
throwError :: (Error e, Monad m) => e -> ResultT e m a
throwFatal :: (Error e, Monad m) => e -> ResultT e m a
mapResult :: (Functor m, Monad m) => (Result e1 a1 -> Result e a) -> ResultT e1 m a1 -> ResultT e m a
class Error a where
- noMsg :: a
- strMsg :: String -> a
lift :: (MonadTrans t, Monad m) => m a -> t m a

Documentation

data Result e a Source #

Result is like Either but with two error states, Fail and Fatal.

Fail is precisely analogous to Left while Fatal has short cut semantics for Alternative.

The idea is that Fatal errors cannot be circumvented by <|> etc.

Constructors

Fatal e
Fail e
Ok a

Instances

Instances details

Monad (Result e) Source #
Instance details Defined in Text.XML.Light.Extractors.Internal.Result Methods (>>=) :: Result e a -> (a -> Result e b) -> Result e b # (>>) :: Result e a -> Result e b -> Result e b # return :: a -> Result e a #
Functor (Result e) Source #
Instance details Defined in Text.XML.Light.Extractors.Internal.Result Methods fmap :: (a -> b) -> Result e a -> Result e b # (<$) :: a -> Result e b -> Result e a #
Applicative (Result e) Source #
Instance details Defined in Text.XML.Light.Extractors.Internal.Result Methods pure :: a -> Result e a # (<>) :: Result e (a -> b) -> Result e a -> Result e b # liftA2 :: (a -> b -> c) -> Result e a -> Result e b -> Result e c # (>) :: Result e a -> Result e b -> Result e b # (<*) :: Result e a -> Result e b -> Result e a #
Error e => Alternative (Result e) Source #
Instance details Defined in Text.XML.Light.Extractors.Internal.Result Methods empty :: Result e a # (<\|>) :: Result e a -> Result e a -> Result e a # some :: Result e a -> Result e [a] # many :: Result e a -> Result e [a] #
(Show e, Show a) => Show (Result e a) Source #
Instance details Defined in Text.XML.Light.Extractors.Internal.Result Methods showsPrec :: Int -> Result e a -> ShowS # show :: Result e a -> String # showList :: [Result e a] -> ShowS #

toEither :: Result a b -> Either a b Source #

Maps Fail and Fatal to Left.

escalate :: Result e a -> Result e a Source #

Maps Fail to Fatal.

data ResultT e m a Source #

Instances

Instances details

Error e => MonadTrans (ResultT e) Source #
Instance details Defined in Text.XML.Light.Extractors.Internal.Result Methods lift :: Monad m => m a -> ResultT e m a #
(Monad m, Error e) => Monad (ResultT e m) Source #
Instance details Defined in Text.XML.Light.Extractors.Internal.Result Methods (>>=) :: ResultT e m a -> (a -> ResultT e m b) -> ResultT e m b # (>>) :: ResultT e m a -> ResultT e m b -> ResultT e m b # return :: a -> ResultT e m a #
Functor m => Functor (ResultT e m) Source #
Instance details Defined in Text.XML.Light.Extractors.Internal.Result Methods fmap :: (a -> b) -> ResultT e m a -> ResultT e m b # (<$) :: a -> ResultT e m b -> ResultT e m a #
(Monad m, Error e) => MonadFail (ResultT e m) Source #
Instance details Defined in Text.XML.Light.Extractors.Internal.Result Methods fail :: String -> ResultT e m a #
(Functor m, Monad m) => Applicative (ResultT e m) Source #
Instance details Defined in Text.XML.Light.Extractors.Internal.Result Methods pure :: a -> ResultT e m a # (<>) :: ResultT e m (a -> b) -> ResultT e m a -> ResultT e m b # liftA2 :: (a -> b -> c) -> ResultT e m a -> ResultT e m b -> ResultT e m c # (>) :: ResultT e m a -> ResultT e m b -> ResultT e m b # (<*) :: ResultT e m a -> ResultT e m b -> ResultT e m a #
(Functor m, Monad m, Error e) => Alternative (ResultT e m) Source #
Instance details Defined in Text.XML.Light.Extractors.Internal.Result Methods empty :: ResultT e m a # (<\|>) :: ResultT e m a -> ResultT e m a -> ResultT e m a # some :: ResultT e m a -> ResultT e m [a] # many :: ResultT e m a -> ResultT e m [a] #
(Error e, Monad m) => MonadPlus (ResultT e m) Source #
Instance details Defined in Text.XML.Light.Extractors.Internal.Result Methods mzero :: ResultT e m a # mplus :: ResultT e m a -> ResultT e m a -> ResultT e m a #

runResultT :: ResultT e m a -> m (Result e a) Source #

throwError :: (Error e, Monad m) => e -> ResultT e m a Source #

throwFatal :: (Error e, Monad m) => e -> ResultT e m a Source #

mapResult :: (Functor m, Monad m) => (Result e1 a1 -> Result e a) -> ResultT e1 m a1 -> ResultT e m a Source #

class Error a where #

An exception to be thrown.

Minimal complete definition: noMsg or strMsg.

Minimal complete definition

Nothing

Methods

noMsg :: a #

Creates an exception without a message. The default implementation is strMsg "".

strMsg :: String -> a #

Creates an exception with a message. The default implementation of strMsg s is noMsg.

Instances

Instances details

Error IOException
Instance details Defined in Control.Monad.Trans.Error Methods noMsg :: IOException # strMsg :: String -> IOException #
Error ExtractionErr Source #
Instance details Defined in Text.XML.Light.Extractors.Internal Methods noMsg :: ExtractionErr # strMsg :: String -> ExtractionErr #
ErrorList a => Error [a]	A string can be thrown as an error.
Instance details Defined in Control.Monad.Trans.Error Methods noMsg :: [a] # strMsg :: String -> [a] #

lift :: (MonadTrans t, Monad m) => m a -> t m a #

Lift a computation from the argument monad to the constructed monad.