Copyright | (C) Edward Kmett 2013-2015 (c) Google Inc. 2012 |
---|---|
License | BSD-style (see the file LICENSE) |
Maintainer | Edward Kmett <ekmett@gmail.com> |
Stability | experimental |
Portability | non-portable |
Safe Haskell | Trustworthy |
Language | Haskell98 |
Synopsis
- newtype CatchT m a = CatchT {
- runCatchT :: m (Either SomeException a)
- type Catch = CatchT Identity
- runCatch :: Catch a -> Either SomeException a
- mapCatchT :: (m (Either SomeException a) -> n (Either SomeException b)) -> CatchT m a -> CatchT n b
- module Control.Monad.Catch
Transformer
The transformers
-style monad transfomer
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!
CatchT | |
|
Instances
MonadTrans CatchT Source # | |
Defined in Control.Monad.Catch.Pure | |
MonadRWS r w s m => MonadRWS r w s (CatchT m) Source # | |
Defined in Control.Monad.Catch.Pure | |
MonadWriter w m => MonadWriter w (CatchT m) Source # | |
MonadState s m => MonadState s (CatchT m) Source # | |
MonadReader e m => MonadReader e (CatchT m) Source # | |
Monad m => Monad (CatchT m) Source # | |
Monad m => Functor (CatchT m) Source # | |
MonadFix m => MonadFix (CatchT m) Source # | |
Defined in Control.Monad.Catch.Pure | |
Monad m => MonadFail (CatchT m) Source # | |
Defined in Control.Monad.Catch.Pure | |
Monad m => Applicative (CatchT m) Source # | |
Foldable m => Foldable (CatchT m) Source # | |
Defined in Control.Monad.Catch.Pure fold :: Monoid m0 => CatchT m m0 -> m0 # foldMap :: Monoid m0 => (a -> m0) -> CatchT m a -> m0 # foldr :: (a -> b -> b) -> b -> CatchT m a -> b # foldr' :: (a -> b -> b) -> b -> CatchT m a -> b # foldl :: (b -> a -> b) -> b -> CatchT m a -> b # foldl' :: (b -> a -> b) -> b -> CatchT m a -> b # foldr1 :: (a -> a -> a) -> CatchT m a -> a # foldl1 :: (a -> a -> a) -> CatchT m a -> a # elem :: Eq a => a -> CatchT m a -> Bool # maximum :: Ord a => CatchT m a -> a # minimum :: Ord a => CatchT m a -> a # | |
(Monad m, Traversable m) => Traversable (CatchT m) Source # | |
MonadIO m => MonadIO (CatchT m) Source # | |
Defined in Control.Monad.Catch.Pure | |
Monad m => Alternative (CatchT m) Source # | |
Monad m => MonadPlus (CatchT m) Source # | |
Monad m => MonadMask (CatchT m) Source # | Note: This instance is only valid if the underlying monad has a single exit point! For example, |
Defined in Control.Monad.Catch.Pure | |
Monad m => MonadCatch (CatchT m) Source # | |
Monad m => MonadThrow (CatchT m) Source # | |
mapCatchT :: (m (Either SomeException a) -> n (Either SomeException b)) -> CatchT m a -> CatchT n b Source #
Typeclass
The mtl style typeclass
module Control.Monad.Catch