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 |
Control.Monad.Catch.Pure
Contents
Description
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!
Constructors
CatchT | |
Fields
|
Instances
MonadTrans CatchT Source # | |
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 # | |
Monad m => MonadFail ( CatchT m) Source # | |
Monad m => Applicative ( CatchT m) Source # | |
Defined in Control.Monad.Catch.Pure |
|
Foldable m => Foldable ( CatchT m) Source # | |
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 # 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 # |
|
( Monad m, Traversable m) => Traversable ( CatchT m) Source # | |
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 # | |
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 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 # | |
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