exceptions-0.10.4: Extensible optionally-pure exceptions

Copyright(C) Edward Kmett 2013-2015 (c) Google Inc. 2012
LicenseBSD-style (see the file LICENSE)
MaintainerEdward Kmett <ekmett@gmail.com>
Stabilityexperimental
Portabilitynon-portable
Safe HaskellTrustworthy
LanguageHaskell98

Control.Monad.Catch.Pure

Contents

Description

This module supplies a 'pure' monad transformer that can be used for mock-testing code that throws exceptions, so long as those exceptions are always thrown with throwM.

Do not mix CatchT with IO. Choose one or the other for the bottom of your transformer stack!

Synopsis

Transformer

The transformers-style monad transfomer

newtype CatchT m a Source #

Add Exception handling abilities to a Monad.

This should never be used in combination with IO. Think of CatchT as an alternative base monad for use with mocking code that solely throws exceptions via throwM.

Note: that IO monad has these abilities already, so stacking CatchT on top of it does not add any value and can possibly be confusing:

>>> (error "Hello!" :: IO ()) `catch` (\(e :: ErrorCall) -> liftIO $ print e)
Hello!
>>> runCatchT $ (error "Hello!" :: CatchT IO ()) `catch` (\(e :: ErrorCall) -> liftIO $ print e)
*** Exception: Hello!
>>> runCatchT $ (throwM (ErrorCall "Hello!") :: CatchT IO ()) `catch` (\(e :: ErrorCall) -> liftIO $ print e)
Hello!

Constructors

CatchT 

Fields

Instances
MonadTrans CatchT Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

lift :: Monad m => m a -> CatchT m a Source #

MonadRWS r w s m => MonadRWS r w s (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

MonadWriter w m => MonadWriter w (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

writer :: (a, w) -> CatchT m a Source #

tell :: w -> CatchT m () Source #

listen :: CatchT m a -> CatchT m (a, w) Source #

pass :: CatchT m (a, w -> w) -> CatchT m a Source #

MonadState s m => MonadState s (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

get :: CatchT m s Source #

put :: s -> CatchT m () Source #

state :: (s -> (a, s)) -> CatchT m a Source #

MonadReader e m => MonadReader e (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

ask :: CatchT m e Source #

local :: (e -> e) -> CatchT m a -> CatchT m a Source #

reader :: (e -> a) -> CatchT m a Source #

Monad m => Monad (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

(>>=) :: CatchT m a -> (a -> CatchT m b) -> CatchT m b Source #

(>>) :: CatchT m a -> CatchT m b -> CatchT m b Source #

return :: a -> CatchT m a Source #

fail :: String -> CatchT m a Source #

Monad m => Functor (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

fmap :: (a -> b) -> CatchT m a -> CatchT m b Source #

(<$) :: a -> CatchT m b -> CatchT m a Source #

MonadFix m => MonadFix (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

mfix :: (a -> CatchT m a) -> CatchT m a Source #

Monad m => MonadFail (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

fail :: String -> CatchT m a Source #

Monad m => Applicative (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

pure :: a -> CatchT m a Source #

(<*>) :: CatchT m (a -> b) -> CatchT m a -> CatchT m b Source #

liftA2 :: (a -> b -> c) -> CatchT m a -> CatchT m b -> CatchT m c Source #

(*>) :: CatchT m a -> CatchT m b -> CatchT m b Source #

(<*) :: CatchT m a -> CatchT m b -> CatchT m a Source #

Foldable m => Foldable (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

fold :: Monoid m0 => CatchT m m0 -> m0 Source #

foldMap :: Monoid m0 => (a -> m0) -> CatchT m a -> m0 Source #

foldr :: (a -> b -> b) -> b -> CatchT m a -> b Source #

foldr' :: (a -> b -> b) -> b -> CatchT m a -> b Source #

foldl :: (b -> a -> b) -> b -> CatchT m a -> b Source #

foldl' :: (b -> a -> b) -> b -> CatchT m a -> b Source #

foldr1 :: (a -> a -> a) -> CatchT m a -> a Source #

foldl1 :: (a -> a -> a) -> CatchT m a -> a Source #

toList :: CatchT m a -> [a] Source #

null :: CatchT m a -> Bool Source #

length :: CatchT m a -> Int Source #

elem :: Eq a => a -> CatchT m a -> Bool Source #

maximum :: Ord a => CatchT m a -> a Source #

minimum :: Ord a => CatchT m a -> a Source #

sum :: Num a => CatchT m a -> a Source #

product :: Num a => CatchT m a -> a Source #

(Monad m, Traversable m) => Traversable (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

traverse :: Applicative f => (a -> f b) -> CatchT m a -> f (CatchT m b) Source #

sequenceA :: Applicative f => CatchT m (f a) -> f (CatchT m a) Source #

mapM :: Monad m0 => (a -> m0 b) -> CatchT m a -> m0 (CatchT m b) Source #

sequence :: Monad m0 => CatchT m (m0 a) -> m0 (CatchT m a) Source #

MonadIO m => MonadIO (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

liftIO :: IO a -> CatchT m a Source #

Monad m => Alternative (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

empty :: CatchT m a Source #

(<|>) :: CatchT m a -> CatchT m a -> CatchT m a Source #

some :: CatchT m a -> CatchT m [a] Source #

many :: CatchT m a -> CatchT m [a] Source #

Monad m => MonadPlus (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

mzero :: CatchT m a Source #

mplus :: CatchT m a -> CatchT m a -> CatchT m a Source #

Monad m => MonadMask (CatchT m) Source #

Note: This instance is only valid if the underlying monad has a single exit point!

For example, IO or Either would be invalid base monads, but Reader or State would be acceptable.

Instance details

Defined in Control.Monad.Catch.Pure

Methods

mask :: ((forall a. CatchT m a -> CatchT m a) -> CatchT m b) -> CatchT m b Source #

uninterruptibleMask :: ((forall a. CatchT m a -> CatchT m a) -> CatchT m b) -> CatchT m b Source #

generalBracket :: CatchT m a -> (a -> ExitCase b -> CatchT m c) -> (a -> CatchT m b) -> CatchT m (b, c) Source #

Monad m => MonadCatch (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

catch :: Exception e => CatchT m a -> (e -> CatchT m a) -> CatchT m a Source #

Monad m => MonadThrow (CatchT m) Source # 
Instance details

Defined in Control.Monad.Catch.Pure

Methods

throwM :: Exception e => e -> CatchT m a Source #

mapCatchT :: (m (Either SomeException a) -> n (Either SomeException b)) -> CatchT m a -> CatchT n b Source #

Map the unwrapped computation using the given function.

runCatchT (mapCatchT f m) = f (runCatchT m)

Typeclass

The mtl style typeclass