| Safe Haskell | Trustworthy |
|---|---|
| Language | Haskell98 |
Pipes.Safe
Description
This module provides an orphan MonadMask instance for Proxy of the
form:
instance (MonadMask m, MonadIO m) => MonadMask (Proxy a' a b' b m) where
Which is needed to implement the instance for MonadSafe for Proxy.
This module also provides generalized versions of some MonadCatch
operations so that you can also protect against premature termination of
connected components. For example, if you protect a readFile computation
using bracket from this module:
-- readFile.hs
import Pipes
import qualified Pipes.Prelude as P
import Pipes.Safe
import qualified System.IO as IO
import Prelude hiding (readFile)
readFile :: FilePath -> Producer' String (SafeT IO) ()
readFile file = bracket
(do h <- IO.openFile file IO.ReadMode
putStrLn $ "{" ++ file ++ " open}"
return h )
(\h -> do
IO.hClose h
putStrLn $ "{" ++ file ++ " closed}" )
P.fromHandle... then this generalized bracket will guard against both exceptions and
premature termination of other pipes:
>>>runSafeT $ runEffect $ readFile "readFile.hs" >-> P.take 4 >-> P.stdoutLn{readFile.hs open} -- readFile.hs import Pipes import qualified Pipes.Prelude as P import Pipes.Safe {readFile.hs closed}
Note that the MonadCatch instance for Proxy provides weaker versions of
mask and uninterruptibleMask that do not completely prevent asynchronous
exceptions. Instead, they provide a weaker guarantee that asynchronous
exceptions will only occur during awaits or yields and
nowhere else. For example, if you write:
mask_ $ do
x <- await
lift $ print x
lift $ print x... then you may receive an asynchronous exception during the await,
but you will not receive an asynchronous exception during or in between the
two print statements. This weaker guarantee suffices to provide
asynchronous exception safety.
Synopsis
- data SafeT m r
- runSafeT :: (MonadMask m, MonadIO m) => SafeT m r -> m r
- runSafeP :: (MonadMask m, MonadIO m) => Effect (SafeT m) r -> Effect' m r
- data ReleaseKey
- class (MonadCatch m, MonadMask m, MonadIO m, MonadIO (Base m)) => MonadSafe m where
- type Base (m :: * -> *) :: * -> *
- liftBase :: Base m r -> m r
- register :: Base m () -> m ReleaseKey
- release :: ReleaseKey -> m ()
- onException :: MonadSafe m => m a -> Base m b -> m a
- tryP :: (MonadSafe m, Exception e) => Proxy a' a b' b m r -> Proxy a' a b' b m (Either e r)
- catchP :: (MonadSafe m, Exception e) => Proxy a' a b' b m r -> (e -> Proxy a' a b' b m r) -> Proxy a' a b' b m r
- finally :: MonadSafe m => m a -> Base m b -> m a
- bracket :: MonadSafe m => Base m a -> (a -> Base m b) -> (a -> m c) -> m c
- bracket_ :: MonadSafe m => Base m a -> Base m b -> m c -> m c
- bracketOnError :: MonadSafe m => Base m a -> (a -> Base m b) -> (a -> m c) -> m c
- catches :: (Foldable f, MonadCatch m) => m a -> f (Handler m a) -> m a
- tryJust :: (MonadCatch m, Exception e) => (e -> Maybe b) -> m a -> m (Either b a)
- handleJust :: (MonadCatch m, Exception e) => (e -> Maybe b) -> (b -> m a) -> m a -> m a
- handleIf :: (MonadCatch m, Exception e) => (e -> Bool) -> (e -> m a) -> m a -> m a
- handleAll :: MonadCatch m => (SomeException -> m a) -> m a -> m a
- handleIOError :: MonadCatch m => (IOError -> m a) -> m a -> m a
- handle :: (MonadCatch m, Exception e) => (e -> m a) -> m a -> m a
- catchJust :: (MonadCatch m, Exception e) => (e -> Maybe b) -> m a -> (b -> m a) -> m a
- catchIf :: (MonadCatch m, Exception e) => (e -> Bool) -> m a -> (e -> m a) -> m a
- catchIOError :: MonadCatch m => m a -> (IOError -> m a) -> m a
- catchAll :: MonadCatch m => m a -> (SomeException -> m a) -> m a
- uninterruptibleMask_ :: MonadMask m => m a -> m a
- mask_ :: MonadMask m => m a -> m a
- class Monad m => MonadThrow (m :: Type -> Type) where
- class MonadThrow m => MonadCatch (m :: Type -> Type) where
- class MonadCatch m => MonadMask (m :: Type -> Type) where
- mask :: ((forall a. m a -> m a) -> m b) -> m b
- uninterruptibleMask :: ((forall a. m a -> m a) -> m b) -> m b
- generalBracket :: m a -> (a -> ExitCase b -> m c) -> (a -> m b) -> m (b, c)
- data ExitCase a
- data Handler (m :: Type -> Type) a = Exception e => Handler (e -> m a)
- data SomeException
- class (Typeable e, Show e) => Exception e where
- toException :: e -> SomeException
- fromException :: SomeException -> Maybe e
- displayException :: e -> String
- data SomeException = Exception e => SomeException e
- class (Typeable e, Show e) => Exception e where
- toException :: e -> SomeException
- fromException :: SomeException -> Maybe e
- displayException :: e -> String
SafeT
SafeT is a monad transformer that extends the base monad with the ability
to register and release finalizers.
All unreleased finalizers are called at the end of the SafeT block, even
in the event of exceptions.
Instances
| MonadTrans SafeT Source # | |
Defined in Pipes.Safe | |
| MonadBase b m => MonadBase b (SafeT m) Source # | |
Defined in Pipes.Safe | |
| MonadBaseControl b m => MonadBaseControl b (SafeT m) Source # | |
| MonadWriter w m => MonadWriter w (SafeT m) Source # | |
| MonadState s m => MonadState s (SafeT m) Source # | |
| MonadError e m => MonadError e (SafeT m) Source # | |
Defined in Pipes.Safe | |
| Monad m => Monad (SafeT m) Source # | |
| Functor m => Functor (SafeT m) Source # | |
| MonadFix m => MonadFix (SafeT m) Source # | |
Defined in Pipes.Safe | |
| MonadFail m => MonadFail (SafeT m) Source # | |
Defined in Pipes.Safe | |
| Applicative m => Applicative (SafeT m) Source # | |
| MonadThrow m => MonadThrow (SafeT m) Source # | |
| MonadCatch m => MonadCatch (SafeT m) Source # | |
| MonadMask m => MonadMask (SafeT m) Source # | |
Defined in Pipes.Safe | |
| MonadPlus m => MonadPlus (SafeT m) Source # | |
| MonadIO m => MonadIO (SafeT m) Source # | |
Defined in Pipes.Safe | |
| PrimMonad m => PrimMonad (SafeT m) Source # | |
| Alternative m => Alternative (SafeT m) Source # | |
| MonadCont m => MonadCont (SafeT m) Source # | |
Defined in Pipes.Safe | |
| (MonadIO m, MonadCatch m, MonadMask m) => MonadSafe (SafeT m) Source # | |
| type PrimState (SafeT m) Source # | |
Defined in Pipes.Safe | |
| type Base (SafeT m) Source # | |
Defined in Pipes.Safe | |
| type StM (SafeT m) a Source # | |
Defined in Pipes.Safe | |
runSafeT :: (MonadMask m, MonadIO m) => SafeT m r -> m r Source #
Run the SafeT monad transformer, executing all unreleased finalizers at
the end of the computation
MonadSafe
data ReleaseKey Source #
class (MonadCatch m, MonadMask m, MonadIO m, MonadIO (Base m)) => MonadSafe m where Source #
Associated Types
type Base (m :: * -> *) :: * -> * Source #
The monad used to run resource management actions, corresponding to the
monad directly beneath SafeT
Methods
liftBase :: Base m r -> m r Source #
Lift an action from the Base monad
register :: Base m () -> m ReleaseKey Source #
register a finalizer, ensuring that the finalizer gets called if the
finalizer is not released before the end of the surrounding SafeT
block.
release :: ReleaseKey -> m () Source #
release a registered finalizer
You can safely call release more than once on the same ReleaseKey.
Every release after the first one does nothing.
Instances
| MonadSafe m => MonadSafe (CatchT m) Source # | |
| (MonadIO m, MonadCatch m, MonadMask m) => MonadSafe (SafeT m) Source # | |
| (MonadSafe m, Monoid w) => MonadSafe (WriterT w m) Source # | |
| MonadSafe m => MonadSafe (StateT s m) Source # | |
| MonadSafe m => MonadSafe (ReaderT i m) Source # | |
| MonadSafe m => MonadSafe (IdentityT m) Source # | |
| (MonadSafe m, Monoid w) => MonadSafe (WriterT w m) Source # | |
| MonadSafe m => MonadSafe (StateT s m) Source # | |
| (MonadSafe m, Monoid w) => MonadSafe (RWST i w s m) Source # | |
| (MonadSafe m, Monoid w) => MonadSafe (RWST i w s m) Source # | |
| MonadSafe m => MonadSafe (Proxy a' a b' b m) Source # | |
Defined in Pipes.Safe | |
Utilities
These utilities let you supply a finalizer that runs in the Base monad
(i.e. the monad directly beneath SafeT). If you don't need to use the
full power of the Base monad and you only need to use to use IO, then
just wrap the finalizer in liftIO, like this:
myAction `finally` (liftIO myFinalizer)
This will lead to a simple inferred type with a single MonadSafe
constraint:
(MonadSafe m) => ...
For examples of this, see the utilities in Pipes.Safe.Prelude.
If you omit the liftIO, the compiler will infer the following constraint
instead:
(MonadSafe m, Base m ~ IO) => ...
This means that this function would require IO directly beneath the
SafeT monad transformer, which might not be what you want.
onException :: MonadSafe m => m a -> Base m b -> m a Source #
Analogous to onException from Control.Monad.Catch, except this also
protects against premature termination
(`onException` io) is a monad morphism.
tryP :: (MonadSafe m, Exception e) => Proxy a' a b' b m r -> Proxy a' a b' b m (Either e r) Source #
Transform a Proxy into one that catches any exceptions caused by its
effects, and returns the resulting exception.
catchP :: (MonadSafe m, Exception e) => Proxy a' a b' b m r -> (e -> Proxy a' a b' b m r) -> Proxy a' a b' b m r Source #
Allows direct handling of exceptions raised by the effects in a Proxy.
finally :: MonadSafe m => m a -> Base m b -> m a Source #
Analogous to finally from Control.Monad.Catch, except this also
protects against premature termination
bracket :: MonadSafe m => Base m a -> (a -> Base m b) -> (a -> m c) -> m c Source #
Analogous to bracket from Control.Monad.Catch, except this also
protects against premature termination
bracket_ :: MonadSafe m => Base m a -> Base m b -> m c -> m c Source #
Analogous to bracket_ from Control.Monad.Catch, except this also
protects against premature termination
bracketOnError :: MonadSafe m => Base m a -> (a -> Base m b) -> (a -> m c) -> m c Source #
Analogous to bracketOnError from Control.Monad.Catch, except this also
protects against premature termination
Re-exports
Control.Monad.Catch re-exports all functions except for the ones that
conflict with the generalized versions provided here (i.e. bracket,
finally, etc.).
Control.Exception re-exports Exception and SomeException.
catches :: (Foldable f, MonadCatch m) => m a -> f (Handler m a) -> m a Source #
Catches different sorts of exceptions. See Control.Exception's catches
tryJust :: (MonadCatch m, Exception e) => (e -> Maybe b) -> m a -> m (Either b a) Source #
A variant of try that takes an exception predicate to select
which exceptions are caught. See Control.Exception's tryJust
handleJust :: (MonadCatch m, Exception e) => (e -> Maybe b) -> (b -> m a) -> m a -> m a Source #
Flipped catchJust. See Control.Exception's handleJust.
handleIf :: (MonadCatch m, Exception e) => (e -> Bool) -> (e -> m a) -> m a -> m a Source #
Flipped catchIf
handleAll :: MonadCatch m => (SomeException -> m a) -> m a -> m a Source #
Flipped catchAll
handleIOError :: MonadCatch m => (IOError -> m a) -> m a -> m a Source #
Flipped catchIOError
handle :: (MonadCatch m, Exception e) => (e -> m a) -> m a -> m a Source #
Flipped catch. See Control.Exception's handle.
catchJust :: (MonadCatch m, Exception e) => (e -> Maybe b) -> m a -> (b -> m a) -> m a Source #
A more generalized way of determining which exceptions to catch at run time.
catchIf :: (MonadCatch m, Exception e) => (e -> Bool) -> m a -> (e -> m a) -> m a Source #
Catch exceptions only if they pass some predicate. Often useful with the
predicates for testing IOError values in System.IO.Error.
catchIOError :: MonadCatch m => m a -> (IOError -> m a) -> m a Source #
Catch all IOError (eqv. IOException) exceptions. Still somewhat too
general, but better than using catchAll. See catchIf for an easy way
of catching specific IOErrors based on the predicates in System.IO.Error.
catchAll :: MonadCatch m => m a -> (SomeException -> m a) -> m a Source #
Catches all exceptions, and somewhat defeats the purpose of the extensible exception system. Use sparingly.
NOTE This catches all exceptions, but if the monad supports other ways of aborting the computation, those other kinds of errors will not be caught.
uninterruptibleMask_ :: MonadMask m => m a -> m a Source #
Like uninterruptibleMask, but does not pass a restore action to the
argument.
mask_ :: MonadMask m => m a -> m a Source #
Like mask, but does not pass a restore action to the argument.
class Monad m => MonadThrow (m :: Type -> Type) where Source #
A class for monads in which exceptions may be thrown.
Instances should obey the following law:
throwM e >> x = throwM e
In other words, throwing an exception short-circuits the rest of the monadic computation.
Methods
throwM :: Exception e => e -> m a Source #
Throw an exception. Note that this throws when this action is run in
the monad m, not when it is applied. It is a generalization of
Control.Exception's throwIO.
Should satisfy the law:
throwM e >> f = throwM e
Instances
class MonadThrow m => MonadCatch (m :: Type -> Type) where Source #
A class for monads which allow exceptions to be caught, in particular
exceptions which were thrown by throwM.
Instances should obey the following law:
catch (throwM e) f = f e
Note that the ability to catch an exception does not guarantee that we can
deal with all possible exit points from a computation. Some monads, such as
continuation-based stacks, allow for more than just a success/failure
strategy, and therefore catch cannot be used by those monads to properly
implement a function such as finally. For more information, see
MonadMask.
Methods
catch :: Exception e => m a -> (e -> m a) -> m a Source #
Provide a handler for exceptions thrown during execution of the first
action. Note that type of the type of the argument to the handler will
constrain which exceptions are caught. See Control.Exception's
catch.
Instances
| MonadCatch IO | |
Defined in Control.Monad.Catch | |
| MonadCatch STM | |
Defined in Control.Monad.Catch | |
| e ~ SomeException => MonadCatch (Either e) | Since: exceptions-0.8.3 |
Defined in Control.Monad.Catch | |
| MonadCatch m => MonadCatch (MaybeT m) | Catches exceptions from the base monad. |
Defined in Control.Monad.Catch | |
| Monad m => MonadCatch (CatchT m) | |
| MonadCatch m => MonadCatch (ListT m) | |
Defined in Control.Monad.Catch | |
| MonadCatch m => MonadCatch (ListT m) | |
| MonadCatch m => MonadCatch (SafeT m) Source # | |
| MonadCatch m => MonadCatch (ExceptT e m) | Catches exceptions from the base monad. |
Defined in Control.Monad.Catch | |
| (MonadCatch m, Monoid w) => MonadCatch (WriterT w m) | |
Defined in Control.Monad.Catch | |
| MonadCatch m => MonadCatch (StateT s m) | |
Defined in Control.Monad.Catch | |
| MonadCatch m => MonadCatch (ReaderT r m) | |
Defined in Control.Monad.Catch | |
| (Error e, MonadCatch m) => MonadCatch (ErrorT e m) | Catches exceptions from the base monad. |
Defined in Control.Monad.Catch | |
| MonadCatch m => MonadCatch (IdentityT m) | |
Defined in Control.Monad.Catch | |
| (MonadCatch m, Monoid w) => MonadCatch (WriterT w m) | |
Defined in Control.Monad.Catch | |
| MonadCatch m => MonadCatch (StateT s m) | |
Defined in Control.Monad.Catch | |
| (MonadCatch m, Monoid w) => MonadCatch (RWST r w s m) | |
Defined in Control.Monad.Catch | |
| (MonadCatch m, Monoid w) => MonadCatch (RWST r w s m) | |
Defined in Control.Monad.Catch | |
| MonadCatch m => MonadCatch (Proxy a' a b' b m) | |
class MonadCatch m => MonadMask (m :: Type -> Type) where Source #
A class for monads which provide for the ability to account for all possible exit points from a computation, and to mask asynchronous exceptions. Continuation-based monads are invalid instances of this class.
Instances should ensure that, in the following code:
fg = f `finally` g
The action g is called regardless of what occurs within f, including
async exceptions. Some monads allow f to abort the computation via other
effects than throwing an exception. For simplicity, we will consider aborting
and throwing an exception to be two forms of "throwing an error".
If f and g both throw an error, the error thrown by fg depends on which
errors we're talking about. In a monad transformer stack, the deeper layers
override the effects of the inner layers; for example, ExceptT e1 (Except
e2) a represents a value of type Either e2 (Either e1 a), so throwing both
an e1 and an e2 will result in Left e2. If f and g both throw an
error from the same layer, instances should ensure that the error from g
wins.
Effects other than throwing an error are also overriden by the deeper layers.
For example, StateT s Maybe a represents a value of type s -> Maybe (a,
s), so if an error thrown from f causes this function to return Nothing,
any changes to the state which f also performed will be erased. As a
result, g will see the state as it was before f. Once g completes,
f's error will be rethrown, so g' state changes will be erased as well.
This is the normal interaction between effects in a monad transformer stack.
By contrast, lifted-base's
version of finally always discards all of g's non-IO effects, and g
never sees any of f's non-IO effects, regardless of the layer ordering and
regardless of whether f throws an error. This is not the result of
interacting effects, but a consequence of MonadBaseControl's approach.
Methods
mask :: ((forall a. m a -> m a) -> m b) -> m b Source #
Runs an action with asynchronous exceptions disabled. The action is
provided a method for restoring the async. environment to what it was
at the mask call. See Control.Exception's mask.
uninterruptibleMask :: ((forall a. m a -> m a) -> m b) -> m b Source #
Like mask, but the masked computation is not interruptible (see
Control.Exception's uninterruptibleMask. WARNING:
Only use if you need to mask exceptions around an interruptible operation
AND you can guarantee the interruptible operation will only block for a
short period of time. Otherwise you render the program/thread unresponsive
and/or unkillable.
Arguments
| :: m a | acquire some resource |
| -> (a -> ExitCase b -> m c) | release the resource, observing the outcome of the inner action |
| -> (a -> m b) | inner action to perform with the resource |
| -> m (b, c) |
A generalized version of bracket which uses ExitCase to distinguish
the different exit cases, and returns the values of both the use and
release actions. In practice, this extra information is rarely needed,
so it is often more convenient to use one of the simpler functions which
are defined in terms of this one, such as bracket, finally, onError,
and bracketOnError.
This function exists because in order to thread their effects through the
execution of bracket, monad transformers need values to be threaded from
use to release and from release to the output value.
NOTE This method was added in version 0.9.0 of this
library. Previously, implementation of functions like bracket
and finally in this module were based on the mask and
uninterruptibleMask functions only, disallowing some classes of
tranformers from having MonadMask instances (notably
multi-exit-point transformers like ExceptT). If you are a
library author, you'll now need to provide an implementation for
this method. The StateT implementation demonstrates most of the
subtleties:
generalBracket acquire release use = StateT $ s0 -> do
((b, _s2), (c, s3)) <- generalBracket
(runStateT acquire s0)
((resource, s1) exitCase -> case exitCase of
ExitCaseSuccess (b, s2) -> runStateT (release resource (ExitCaseSuccess b)) s2
-- In the two other cases, the base monad overrides use's state
-- changes and the state reverts to s1.
ExitCaseException e -> runStateT (release resource (ExitCaseException e)) s1
ExitCaseAbort -> runStateT (release resource ExitCaseAbort) s1
)
((resource, s1) -> runStateT (use resource) s1)
return ((b, c), s3)
The StateT s m implementation of generalBracket delegates to the m
implementation of generalBracket. The acquire, use, and release
arguments given to StateT's implementation produce actions of type
StateT s m a, StateT s m b, and StateT s m c. In order to run those
actions in the base monad, we need to call runStateT, from which we
obtain actions of type m (a, s), m (b, s), and m (c, s). Since each
action produces the next state, it is important to feed the state produced
by the previous action to the next action.
In the ExitCaseSuccess case, the state starts at s0, flows through
acquire to become s1, flows through use to become s2, and finally
flows through release to become s3. In the other two cases, release
does not receive the value s2, so its action cannot see the state changes
performed by use. This is fine, because in those two cases, an error was
thrown in the base monad, so as per the usual interaction between effects
in a monad transformer stack, those state changes get reverted. So we start
from s1 instead.
Finally, the m implementation of generalBracket returns the pairs
(b, s) and (c, s). For monad transformers other than StateT, this
will be some other type representing the effects and values performed and
returned by the use and release actions. The effect part of the use
result, in this case _s2, usually needs to be discarded, since those
effects have already been incorporated in the release action.
The only effect which is intentionally not incorporated in the release
action is the effect of throwing an error. In that case, the error must be
re-thrown. One subtlety which is easy to miss is that in the case in which
use and release both throw an error, the error from release should
take priority. Here is an implementation for ExceptT which demonstrates
how to do this.
generalBracket acquire release use = ExceptT $ do
(eb, ec) <- generalBracket
(runExceptT acquire)
(eresource exitCase -> case eresource of
Left e -> return (Left e) -- nothing to release, acquire didn't succeed
Right resource -> case exitCase of
ExitCaseSuccess (Right b) -> runExceptT (release resource (ExitCaseSuccess b))
ExitCaseException e -> runExceptT (release resource (ExitCaseException e))
_ -> runExceptT (release resource ExitCaseAbort))
(either (return . Left) (runExceptT . use))
return $ do
-- The order in which we perform those two Either effects determines
-- which error will win if they are both Lefts. We want the error from
-- release to win.
c <- ec
b <- eb
return (b, c)
Since: exceptions-0.9.0
Instances
| MonadMask IO | |
Defined in Control.Monad.Catch Methods mask :: ((forall a. IO a -> IO a) -> IO b) -> IO b Source # uninterruptibleMask :: ((forall a. IO a -> IO a) -> IO b) -> IO b Source # generalBracket :: IO a -> (a -> ExitCase b -> IO c) -> (a -> IO b) -> IO (b, c) Source # | |
| e ~ SomeException => MonadMask (Either e) | Since: exceptions-0.8.3 |
Defined in Control.Monad.Catch Methods mask :: ((forall a. Either e a -> Either e a) -> Either e b) -> Either e b Source # uninterruptibleMask :: ((forall a. Either e a -> Either e a) -> Either e b) -> Either e b Source # generalBracket :: Either e a -> (a -> ExitCase b -> Either e c) -> (a -> Either e b) -> Either e (b, c) Source # | |
| MonadMask m => MonadMask (MaybeT m) | Since: exceptions-0.10.0 |
Defined in Control.Monad.Catch Methods mask :: ((forall a. MaybeT m a -> MaybeT m a) -> MaybeT m b) -> MaybeT m b Source # uninterruptibleMask :: ((forall a. MaybeT m a -> MaybeT m a) -> MaybeT m b) -> MaybeT m b Source # generalBracket :: MaybeT m a -> (a -> ExitCase b -> MaybeT m c) -> (a -> MaybeT m b) -> MaybeT m (b, c) Source # | |
| Monad m => MonadMask (CatchT m) | 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 # | |
| MonadMask m => MonadMask (SafeT m) Source # | |
Defined in Pipes.Safe | |
| MonadMask m => MonadMask (ExceptT e m) | Since: exceptions-0.9.0 |
Defined in Control.Monad.Catch Methods mask :: ((forall a. ExceptT e m a -> ExceptT e m a) -> ExceptT e m b) -> ExceptT e m b Source # uninterruptibleMask :: ((forall a. ExceptT e m a -> ExceptT e m a) -> ExceptT e m b) -> ExceptT e m b Source # generalBracket :: ExceptT e m a -> (a -> ExitCase b -> ExceptT e m c) -> (a -> ExceptT e m b) -> ExceptT e m (b, c) Source # | |
| (MonadMask m, Monoid w) => MonadMask (WriterT w m) | |
Defined in Control.Monad.Catch Methods mask :: ((forall a. WriterT w m a -> WriterT w m a) -> WriterT w m b) -> WriterT w m b Source # uninterruptibleMask :: ((forall a. WriterT w m a -> WriterT w m a) -> WriterT w m b) -> WriterT w m b Source # generalBracket :: WriterT w m a -> (a -> ExitCase b -> WriterT w m c) -> (a -> WriterT w m b) -> WriterT w m (b, c) Source # | |
| MonadMask m => MonadMask (StateT s m) | |
Defined in Control.Monad.Catch Methods mask :: ((forall a. StateT s m a -> StateT s m a) -> StateT s m b) -> StateT s m b Source # uninterruptibleMask :: ((forall a. StateT s m a -> StateT s m a) -> StateT s m b) -> StateT s m b Source # generalBracket :: StateT s m a -> (a -> ExitCase b -> StateT s m c) -> (a -> StateT s m b) -> StateT s m (b, c) Source # | |
| MonadMask m => MonadMask (ReaderT r m) | |
Defined in Control.Monad.Catch Methods mask :: ((forall a. ReaderT r m a -> ReaderT r m a) -> ReaderT r m b) -> ReaderT r m b Source # uninterruptibleMask :: ((forall a. ReaderT r m a -> ReaderT r m a) -> ReaderT r m b) -> ReaderT r m b Source # generalBracket :: ReaderT r m a -> (a -> ExitCase b -> ReaderT r m c) -> (a -> ReaderT r m b) -> ReaderT r m (b, c) Source # | |
| (Error e, MonadMask m) => MonadMask (ErrorT e m) | |
Defined in Control.Monad.Catch Methods mask :: ((forall a. ErrorT e m a -> ErrorT e m a) -> ErrorT e m b) -> ErrorT e m b Source # uninterruptibleMask :: ((forall a. ErrorT e m a -> ErrorT e m a) -> ErrorT e m b) -> ErrorT e m b Source # generalBracket :: ErrorT e m a -> (a -> ExitCase b -> ErrorT e m c) -> (a -> ErrorT e m b) -> ErrorT e m (b, c) Source # | |
| MonadMask m => MonadMask (IdentityT m) | |
Defined in Control.Monad.Catch Methods mask :: ((forall a. IdentityT m a -> IdentityT m a) -> IdentityT m b) -> IdentityT m b Source # uninterruptibleMask :: ((forall a. IdentityT m a -> IdentityT m a) -> IdentityT m b) -> IdentityT m b Source # generalBracket :: IdentityT m a -> (a -> ExitCase b -> IdentityT m c) -> (a -> IdentityT m b) -> IdentityT m (b, c) Source # | |
| (MonadMask m, Monoid w) => MonadMask (WriterT w m) | |
Defined in Control.Monad.Catch Methods mask :: ((forall a. WriterT w m a -> WriterT w m a) -> WriterT w m b) -> WriterT w m b Source # uninterruptibleMask :: ((forall a. WriterT w m a -> WriterT w m a) -> WriterT w m b) -> WriterT w m b Source # generalBracket :: WriterT w m a -> (a -> ExitCase b -> WriterT w m c) -> (a -> WriterT w m b) -> WriterT w m (b, c) Source # | |
| MonadMask m => MonadMask (StateT s m) | |
Defined in Control.Monad.Catch Methods mask :: ((forall a. StateT s m a -> StateT s m a) -> StateT s m b) -> StateT s m b Source # uninterruptibleMask :: ((forall a. StateT s m a -> StateT s m a) -> StateT s m b) -> StateT s m b Source # generalBracket :: StateT s m a -> (a -> ExitCase b -> StateT s m c) -> (a -> StateT s m b) -> StateT s m (b, c) Source # | |
| (MonadMask m, Monoid w) => MonadMask (RWST r w s m) | |
Defined in Control.Monad.Catch Methods mask :: ((forall a. RWST r w s m a -> RWST r w s m a) -> RWST r w s m b) -> RWST r w s m b Source # uninterruptibleMask :: ((forall a. RWST r w s m a -> RWST r w s m a) -> RWST r w s m b) -> RWST r w s m b Source # generalBracket :: RWST r w s m a -> (a -> ExitCase b -> RWST r w s m c) -> (a -> RWST r w s m b) -> RWST r w s m (b, c) Source # | |
| (MonadMask m, Monoid w) => MonadMask (RWST r w s m) | |
Defined in Control.Monad.Catch Methods mask :: ((forall a. RWST r w s m a -> RWST r w s m a) -> RWST r w s m b) -> RWST r w s m b Source # uninterruptibleMask :: ((forall a. RWST r w s m a -> RWST r w s m a) -> RWST r w s m b) -> RWST r w s m b Source # generalBracket :: RWST r w s m a -> (a -> ExitCase b -> RWST r w s m c) -> (a -> RWST r w s m b) -> RWST r w s m (b, c) Source # | |
| (MonadMask m, MonadIO m) => MonadMask (Proxy a' a b' b m) Source # | |
Defined in Pipes.Safe Methods mask :: ((forall a0. Proxy a' a b' b m a0 -> Proxy a' a b' b m a0) -> Proxy a' a b' b m b0) -> Proxy a' a b' b m b0 Source # uninterruptibleMask :: ((forall a0. Proxy a' a b' b m a0 -> Proxy a' a b' b m a0) -> Proxy a' a b' b m b0) -> Proxy a' a b' b m b0 Source # generalBracket :: Proxy a' a b' b m a0 -> (a0 -> ExitCase b0 -> Proxy a' a b' b m c) -> (a0 -> Proxy a' a b' b m b0) -> Proxy a' a b' b m (b0, c) Source # | |
A MonadMask computation may either succeed with a value, abort with an
exception, or abort for some other reason. For example, in ExceptT e IO
you can use throwM to abort with an exception (ExitCaseException) or
throwE to abort with a value of type e
(ExitCaseAbort).
Constructors
| ExitCaseSuccess a | |
| ExitCaseException SomeException | |
| ExitCaseAbort |
data SomeException #
Instances
| Show SomeException | |
Defined in GHC.Exception.Type Methods showsPrec :: Int -> SomeException -> ShowS show :: SomeException -> String showList :: [SomeException] -> ShowS | |
| Exception SomeException | |
Defined in GHC.Exception.Type Methods toException :: SomeException -> SomeException # fromException :: SomeException -> Maybe SomeException # displayException :: SomeException -> String # | |
class (Typeable e, Show e) => Exception e where #
Minimal complete definition
Nothing
Methods
toException :: e -> SomeException #
fromException :: SomeException -> Maybe e #
displayException :: e -> String #
Instances
| Exception SomeException | |
Defined in GHC.Exception.Type Methods toException :: SomeException -> SomeException # fromException :: SomeException -> Maybe SomeException # displayException :: SomeException -> String # | |
| Exception ArithException | |
Defined in GHC.Exception.Type Methods toException :: ArithException -> SomeException # fromException :: SomeException -> Maybe ArithException # displayException :: ArithException -> String # | |
| Exception AllocationLimitExceeded | |
Defined in GHC.IO.Exception Methods toException :: AllocationLimitExceeded -> SomeException # fromException :: SomeException -> Maybe AllocationLimitExceeded # displayException :: AllocationLimitExceeded -> String # | |
| Exception ArrayException | |
Defined in GHC.IO.Exception Methods toException :: ArrayException -> SomeException # fromException :: SomeException -> Maybe ArrayException # displayException :: ArrayException -> String # | |
| Exception AssertionFailed | |
Defined in GHC.IO.Exception Methods toException :: AssertionFailed -> SomeException # fromException :: SomeException -> Maybe AssertionFailed # displayException :: AssertionFailed -> String # | |
| Exception AsyncException | |
Defined in GHC.IO.Exception Methods toException :: AsyncException -> SomeException # fromException :: SomeException -> Maybe AsyncException # displayException :: AsyncException -> String # | |
| Exception BlockedIndefinitelyOnMVar | |
Defined in GHC.IO.Exception Methods toException :: BlockedIndefinitelyOnMVar -> SomeException # fromException :: SomeException -> Maybe BlockedIndefinitelyOnMVar # displayException :: BlockedIndefinitelyOnMVar -> String # | |
| Exception BlockedIndefinitelyOnSTM | |
Defined in GHC.IO.Exception Methods toException :: BlockedIndefinitelyOnSTM -> SomeException # fromException :: SomeException -> Maybe BlockedIndefinitelyOnSTM # displayException :: BlockedIndefinitelyOnSTM -> String # | |
| Exception CompactionFailed | |
Defined in GHC.IO.Exception Methods toException :: CompactionFailed -> SomeException # fromException :: SomeException -> Maybe CompactionFailed # displayException :: CompactionFailed -> String # | |
| Exception Deadlock | |
Defined in GHC.IO.Exception Methods toException :: Deadlock -> SomeException # fromException :: SomeException -> Maybe Deadlock # displayException :: Deadlock -> String # | |
| Exception IOException | |
Defined in GHC.IO.Exception Methods toException :: IOException -> SomeException # fromException :: SomeException -> Maybe IOException # displayException :: IOException -> String # | |
| Exception SomeAsyncException | |
Defined in GHC.IO.Exception Methods toException :: SomeAsyncException -> SomeException # fromException :: SomeException -> Maybe SomeAsyncException # displayException :: SomeAsyncException -> String # | |
| Exception Void | |
Defined in Data.Void Methods toException :: Void -> SomeException # fromException :: SomeException -> Maybe Void # displayException :: Void -> String # | |
| Exception ExitCode | |
Defined in GHC.IO.Exception Methods toException :: ExitCode -> SomeException # fromException :: SomeException -> Maybe ExitCode # displayException :: ExitCode -> String # | |
| Exception FixIOException | |
Defined in GHC.IO.Exception Methods toException :: FixIOException -> SomeException # fromException :: SomeException -> Maybe FixIOException # displayException :: FixIOException -> String # | |
data SomeException #
Constructors
| Exception e => SomeException e |
Instances
| Show SomeException | |
Defined in GHC.Exception.Type Methods showsPrec :: Int -> SomeException -> ShowS show :: SomeException -> String showList :: [SomeException] -> ShowS | |
| Exception SomeException | |
Defined in GHC.Exception.Type Methods toException :: SomeException -> SomeException # fromException :: SomeException -> Maybe SomeException # displayException :: SomeException -> String # | |
class (Typeable e, Show e) => Exception e where #
Minimal complete definition
Nothing
Methods
toException :: e -> SomeException #
fromException :: SomeException -> Maybe e #
displayException :: e -> String #
Instances
| Exception SomeException | |
Defined in GHC.Exception.Type Methods toException :: SomeException -> SomeException # fromException :: SomeException -> Maybe SomeException # displayException :: SomeException -> String # | |
| Exception ArithException | |
Defined in GHC.Exception.Type Methods toException :: ArithException -> SomeException # fromException :: SomeException -> Maybe ArithException # displayException :: ArithException -> String # | |
| Exception AllocationLimitExceeded | |
Defined in GHC.IO.Exception Methods toException :: AllocationLimitExceeded -> SomeException # fromException :: SomeException -> Maybe AllocationLimitExceeded # displayException :: AllocationLimitExceeded -> String # | |
| Exception ArrayException | |
Defined in GHC.IO.Exception Methods toException :: ArrayException -> SomeException # fromException :: SomeException -> Maybe ArrayException # displayException :: ArrayException -> String # | |
| Exception AssertionFailed | |
Defined in GHC.IO.Exception Methods toException :: AssertionFailed -> SomeException # fromException :: SomeException -> Maybe AssertionFailed # displayException :: AssertionFailed -> String # | |
| Exception AsyncException | |
Defined in GHC.IO.Exception Methods toException :: AsyncException -> SomeException # fromException :: SomeException -> Maybe AsyncException # displayException :: AsyncException -> String # | |
| Exception BlockedIndefinitelyOnMVar | |
Defined in GHC.IO.Exception Methods toException :: BlockedIndefinitelyOnMVar -> SomeException # fromException :: SomeException -> Maybe BlockedIndefinitelyOnMVar # displayException :: BlockedIndefinitelyOnMVar -> String # | |
| Exception BlockedIndefinitelyOnSTM | |
Defined in GHC.IO.Exception Methods toException :: BlockedIndefinitelyOnSTM -> SomeException # fromException :: SomeException -> Maybe BlockedIndefinitelyOnSTM # displayException :: BlockedIndefinitelyOnSTM -> String # | |
| Exception CompactionFailed | |
Defined in GHC.IO.Exception Methods toException :: CompactionFailed -> SomeException # fromException :: SomeException -> Maybe CompactionFailed # displayException :: CompactionFailed -> String # | |
| Exception Deadlock | |
Defined in GHC.IO.Exception Methods toException :: Deadlock -> SomeException # fromException :: SomeException -> Maybe Deadlock # displayException :: Deadlock -> String # | |
| Exception IOException | |
Defined in GHC.IO.Exception Methods toException :: IOException -> SomeException # fromException :: SomeException -> Maybe IOException # displayException :: IOException -> String # | |
| Exception SomeAsyncException | |
Defined in GHC.IO.Exception Methods toException :: SomeAsyncException -> SomeException # fromException :: SomeException -> Maybe SomeAsyncException # displayException :: SomeAsyncException -> String # | |
| Exception Void | |
Defined in Data.Void Methods toException :: Void -> SomeException # fromException :: SomeException -> Maybe Void # displayException :: Void -> String # | |
| Exception ExitCode | |
Defined in GHC.IO.Exception Methods toException :: ExitCode -> SomeException # fromException :: SomeException -> Maybe ExitCode # displayException :: ExitCode -> String # | |
| Exception FixIOException | |
Defined in GHC.IO.Exception Methods toException :: FixIOException -> SomeException # fromException :: SomeException -> Maybe FixIOException # displayException :: FixIOException -> String # | |
Orphan instances
| (MonadMask m, MonadIO m) => MonadMask (Proxy a' a b' b m) Source # | |
Methods mask :: ((forall a0. Proxy a' a b' b m a0 -> Proxy a' a b' b m a0) -> Proxy a' a b' b m b0) -> Proxy a' a b' b m b0 Source # uninterruptibleMask :: ((forall a0. Proxy a' a b' b m a0 -> Proxy a' a b' b m a0) -> Proxy a' a b' b m b0) -> Proxy a' a b' b m b0 Source # generalBracket :: Proxy a' a b' b m a0 -> (a0 -> ExitCase b0 -> Proxy a' a b' b m c) -> (a0 -> Proxy a' a b' b m b0) -> Proxy a' a b' b m (b0, c) Source # | |