Copyright | © Anders Kaseorg 2010 |
---|---|
License | BSD-style |
Maintainer | Anders Kaseorg <andersk@mit.edu> |
Stability | experimental |
Portability | non-portable (extended exceptions) |
Safe Haskell | Safe-Inferred |
Language | Haskell2010 |
This is a wrapped version of Control.Exception with types generalized
from IO
to all monads in MonadPeelIO
.
Synopsis
- assert :: Bool -> a -> a
- allowInterrupt :: IO ()
- newtype TypeError = TypeError String
- newtype RecUpdError = RecUpdError String
- newtype RecSelError = RecSelError String
- newtype RecConError = RecConError String
- newtype PatternMatchFail = PatternMatchFail String
- data NonTermination = NonTermination
- newtype NoMethodError = NoMethodError String
- data NestedAtomically = NestedAtomically
- mapException :: (Exception e1, Exception e2) => (e1 -> e2) -> a -> a
- throwTo :: Exception e => ThreadId -> e -> IO ()
- data SomeAsyncException = Exception e => SomeAsyncException e
- data Deadlock = Deadlock
- newtype CompactionFailed = CompactionFailed String
- data BlockedIndefinitelyOnSTM = BlockedIndefinitelyOnSTM
- data BlockedIndefinitelyOnMVar = BlockedIndefinitelyOnMVar
- data AsyncException
- newtype AssertionFailed = AssertionFailed String
- data ArrayException
- data AllocationLimitExceeded = AllocationLimitExceeded
- asyncExceptionToException :: Exception e => e -> SomeException
- asyncExceptionFromException :: Exception e => SomeException -> Maybe e
- data MaskingState
- uninterruptibleMask_ :: IO a -> IO a
- uninterruptibleMask :: ((forall a. IO a -> IO a) -> IO b) -> IO b
- mask_ :: IO a -> IO a
- mask :: ((forall a. IO a -> IO a) -> IO b) -> IO b
- interruptible :: IO a -> IO a
- getMaskingState :: IO MaskingState
- data IOException
- data ErrorCall where
- throw :: forall (r :: RuntimeRep) (a :: TYPE r) e. Exception e => e -> a
- class (Typeable e, Show e) => Exception e where
- toException :: e -> SomeException
- fromException :: SomeException -> Maybe e
- displayException :: e -> String
- data ArithException
- data SomeException = Exception e => SomeException e
- throwIO :: (MonadIO m, Exception e) => e -> m a
- ioError :: MonadIO m => IOError -> m a
- catch :: (MonadPeelIO m, Exception e) => m a -> (e -> m a) -> m a
- catches :: MonadPeelIO m => m a -> [Handler m a] -> m a
- data Handler m a = forall e.Exception e => Handler (e -> m a)
- catchJust :: (MonadPeelIO m, Exception e) => (e -> Maybe b) -> m a -> (b -> m a) -> m a
- handle :: (MonadPeelIO m, Exception e) => (e -> m a) -> m a -> m a
- handleJust :: (MonadPeelIO m, Exception e) => (e -> Maybe b) -> (b -> m a) -> m a -> m a
- try :: (MonadPeelIO m, Exception e) => m a -> m (Either e a)
- tryJust :: (MonadPeelIO m, Exception e) => (e -> Maybe b) -> m a -> m (Either b a)
- evaluate :: MonadIO m => a -> m a
- bracket :: MonadPeelIO m => m a -> (a -> m b) -> (a -> m c) -> m c
- bracket_ :: MonadPeelIO m => m a -> m b -> m c -> m c
- bracketOnError :: MonadPeelIO m => m a -> (a -> m b) -> (a -> m c) -> m c
- finally :: MonadPeelIO m => m a -> m b -> m a
- onException :: MonadPeelIO m => m a -> m b -> m a
Documentation
If the first argument evaluates to True
, then the result is the
second argument. Otherwise an AssertionFailed
exception
is raised, containing a String
with the source file and line number of the
call to assert
.
Assertions can normally be turned on or off with a compiler flag
(for GHC, assertions are normally on unless optimisation is turned on
with -O
or the -fignore-asserts
option is given). When assertions are turned off, the first
argument to assert
is ignored, and the second argument is
returned as the result.
allowInterrupt :: IO () #
When invoked inside mask
, this function allows a masked
asynchronous exception to be raised, if one exists. It is
equivalent to performing an interruptible operation (see
#interruptible), but does not involve any actual blocking.
When called outside mask
, or inside uninterruptibleMask
, this
function has no effect.
Since: base-4.4.0.0
An expression that didn't typecheck during compile time was called.
This is only possible with -fdefer-type-errors. The String
gives
details about the failed type check.
Since: base-4.9.0.0
Instances
Exception TypeError | Since: base-4.9.0.0 |
Defined in Control.Exception.Base toException :: TypeError -> SomeException # fromException :: SomeException -> Maybe TypeError # displayException :: TypeError -> String # | |
Show TypeError | Since: base-4.9.0.0 |
newtype RecUpdError #
A record update was performed on a constructor without the
appropriate field. This can only happen with a datatype with
multiple constructors, where some fields are in one constructor
but not another. The String
gives information about the source
location of the record update.
Instances
Exception RecUpdError | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show RecUpdError | Since: base-4.0 |
Defined in Control.Exception.Base showsPrec :: Int -> RecUpdError -> ShowS # show :: RecUpdError -> String # showList :: [RecUpdError] -> ShowS # |
newtype RecSelError #
A record selector was applied to a constructor without the
appropriate field. This can only happen with a datatype with
multiple constructors, where some fields are in one constructor
but not another. The String
gives information about the source
location of the record selector.
Instances
Exception RecSelError | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show RecSelError | Since: base-4.0 |
Defined in Control.Exception.Base showsPrec :: Int -> RecSelError -> ShowS # show :: RecSelError -> String # showList :: [RecSelError] -> ShowS # |
newtype RecConError #
An uninitialised record field was used. The String
gives
information about the source location where the record was
constructed.
Instances
Exception RecConError | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show RecConError | Since: base-4.0 |
Defined in Control.Exception.Base showsPrec :: Int -> RecConError -> ShowS # show :: RecConError -> String # showList :: [RecConError] -> ShowS # |
newtype PatternMatchFail #
A pattern match failed. The String
gives information about the
source location of the pattern.
Instances
Exception PatternMatchFail | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show PatternMatchFail | Since: base-4.0 |
Defined in Control.Exception.Base showsPrec :: Int -> PatternMatchFail -> ShowS # show :: PatternMatchFail -> String # showList :: [PatternMatchFail] -> ShowS # |
data NonTermination #
Thrown when the runtime system detects that the computation is guaranteed not to terminate. Note that there is no guarantee that the runtime system will notice whether any given computation is guaranteed to terminate or not.
Instances
Exception NonTermination | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show NonTermination | Since: base-4.0 |
Defined in Control.Exception.Base showsPrec :: Int -> NonTermination -> ShowS # show :: NonTermination -> String # showList :: [NonTermination] -> ShowS # |
newtype NoMethodError #
A class method without a definition (neither a default definition,
nor a definition in the appropriate instance) was called. The
String
gives information about which method it was.
Instances
Exception NoMethodError | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show NoMethodError | Since: base-4.0 |
Defined in Control.Exception.Base showsPrec :: Int -> NoMethodError -> ShowS # show :: NoMethodError -> String # showList :: [NoMethodError] -> ShowS # |
data NestedAtomically #
Thrown when the program attempts to call atomically
, from the stm
package, inside another call to atomically
.
Instances
Exception NestedAtomically | Since: base-4.0 |
Defined in Control.Exception.Base | |
Show NestedAtomically | Since: base-4.0 |
Defined in Control.Exception.Base showsPrec :: Int -> NestedAtomically -> ShowS # show :: NestedAtomically -> String # showList :: [NestedAtomically] -> ShowS # |
mapException :: (Exception e1, Exception e2) => (e1 -> e2) -> a -> a #
This function maps one exception into another as proposed in the paper "A semantics for imprecise exceptions".
throwTo :: Exception e => ThreadId -> e -> IO () #
throwTo
raises an arbitrary exception in the target thread (GHC only).
Exception delivery synchronizes between the source and target thread:
throwTo
does not return until the exception has been raised in the
target thread. The calling thread can thus be certain that the target
thread has received the exception. Exception delivery is also atomic
with respect to other exceptions. Atomicity is a useful property to have
when dealing with race conditions: e.g. if there are two threads that
can kill each other, it is guaranteed that only one of the threads
will get to kill the other.
Whatever work the target thread was doing when the exception was raised is not lost: the computation is suspended until required by another thread.
If the target thread is currently making a foreign call, then the
exception will not be raised (and hence throwTo
will not return)
until the call has completed. This is the case regardless of whether
the call is inside a mask
or not. However, in GHC a foreign call
can be annotated as interruptible
, in which case a throwTo
will
cause the RTS to attempt to cause the call to return; see the GHC
documentation for more details.
Important note: the behaviour of throwTo
differs from that described in
the paper "Asynchronous exceptions in Haskell"
(http://research.microsoft.com/~simonpj/Papers/asynch-exns.htm).
In the paper, throwTo
is non-blocking; but the library implementation adopts
a more synchronous design in which throwTo
does not return until the exception
is received by the target thread. The trade-off is discussed in Section 9 of the paper.
Like any blocking operation, throwTo
is therefore interruptible (see Section 5.3 of
the paper). Unlike other interruptible operations, however, throwTo
is always interruptible, even if it does not actually block.
There is no guarantee that the exception will be delivered promptly,
although the runtime will endeavour to ensure that arbitrary
delays don't occur. In GHC, an exception can only be raised when a
thread reaches a safe point, where a safe point is where memory
allocation occurs. Some loops do not perform any memory allocation
inside the loop and therefore cannot be interrupted by a throwTo
.
If the target of throwTo
is the calling thread, then the behaviour
is the same as throwIO
, except that the exception
is thrown as an asynchronous exception. This means that if there is
an enclosing pure computation, which would be the case if the current
IO operation is inside unsafePerformIO
or unsafeInterleaveIO
, that
computation is not permanently replaced by the exception, but is
suspended as if it had received an asynchronous exception.
Note that if throwTo
is called with the current thread as the
target, the exception will be thrown even if the thread is currently
inside mask
or uninterruptibleMask
.
data SomeAsyncException #
Superclass for asynchronous exceptions.
Since: base-4.7.0.0
Exception e => SomeAsyncException e |
Instances
Exception SomeAsyncException | Since: base-4.7.0.0 |
Defined in GHC.IO.Exception | |
Show SomeAsyncException | Since: base-4.7.0.0 |
Defined in GHC.IO.Exception showsPrec :: Int -> SomeAsyncException -> ShowS # show :: SomeAsyncException -> String # showList :: [SomeAsyncException] -> ShowS # |
There are no runnable threads, so the program is deadlocked.
The Deadlock
exception is raised in the main thread only.
Instances
Exception Deadlock | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception toException :: Deadlock -> SomeException # fromException :: SomeException -> Maybe Deadlock # displayException :: Deadlock -> String # | |
Show Deadlock | Since: base-4.1.0.0 |
newtype CompactionFailed #
Compaction found an object that cannot be compacted. Functions
cannot be compacted, nor can mutable objects or pinned objects.
See compact
.
Since: base-4.10.0.0
Instances
Exception CompactionFailed | Since: base-4.10.0.0 |
Defined in GHC.IO.Exception | |
Show CompactionFailed | Since: base-4.10.0.0 |
Defined in GHC.IO.Exception showsPrec :: Int -> CompactionFailed -> ShowS # show :: CompactionFailed -> String # showList :: [CompactionFailed] -> ShowS # |
data BlockedIndefinitelyOnSTM #
The thread is waiting to retry an STM transaction, but there are no
other references to any TVar
s involved, so it can't ever continue.
Instances
Exception BlockedIndefinitelyOnSTM | Since: base-4.1.0.0 |
Show BlockedIndefinitelyOnSTM | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception showsPrec :: Int -> BlockedIndefinitelyOnSTM -> ShowS # show :: BlockedIndefinitelyOnSTM -> String # showList :: [BlockedIndefinitelyOnSTM] -> ShowS # |
data BlockedIndefinitelyOnMVar #
The thread is blocked on an MVar
, but there are no other references
to the MVar
so it can't ever continue.
Instances
Exception BlockedIndefinitelyOnMVar | Since: base-4.1.0.0 |
Show BlockedIndefinitelyOnMVar | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception showsPrec :: Int -> BlockedIndefinitelyOnMVar -> ShowS # show :: BlockedIndefinitelyOnMVar -> String # showList :: [BlockedIndefinitelyOnMVar] -> ShowS # |
data AsyncException #
Asynchronous exceptions.
StackOverflow | The current thread's stack exceeded its limit. Since an exception has been raised, the thread's stack will certainly be below its limit again, but the programmer should take remedial action immediately. |
HeapOverflow | The program's heap is reaching its limit, and the program should take action to reduce the amount of live data it has. Notes:
|
ThreadKilled | This exception is raised by another thread
calling |
UserInterrupt | This exception is raised by default in the main thread of the program when the user requests to terminate the program via the usual mechanism(s) (e.g. Control-C in the console). |
Instances
Exception AsyncException | Since: base-4.7.0.0 |
Defined in GHC.IO.Exception | |
Show AsyncException | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception showsPrec :: Int -> AsyncException -> ShowS # show :: AsyncException -> String # showList :: [AsyncException] -> ShowS # | |
Eq AsyncException | Since: base-4.2.0.0 |
Defined in GHC.IO.Exception (==) :: AsyncException -> AsyncException -> Bool # (/=) :: AsyncException -> AsyncException -> Bool # | |
Ord AsyncException | Since: base-4.2.0.0 |
Defined in GHC.IO.Exception compare :: AsyncException -> AsyncException -> Ordering # (<) :: AsyncException -> AsyncException -> Bool # (<=) :: AsyncException -> AsyncException -> Bool # (>) :: AsyncException -> AsyncException -> Bool # (>=) :: AsyncException -> AsyncException -> Bool # max :: AsyncException -> AsyncException -> AsyncException # min :: AsyncException -> AsyncException -> AsyncException # |
newtype AssertionFailed #
Instances
Exception AssertionFailed | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
Show AssertionFailed | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception showsPrec :: Int -> AssertionFailed -> ShowS # show :: AssertionFailed -> String # showList :: [AssertionFailed] -> ShowS # |
data ArrayException #
Exceptions generated by array operations
IndexOutOfBounds String | An attempt was made to index an array outside its declared bounds. |
UndefinedElement String | An attempt was made to evaluate an element of an array that had not been initialized. |
Instances
Exception ArrayException | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
Show ArrayException | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception showsPrec :: Int -> ArrayException -> ShowS # show :: ArrayException -> String # showList :: [ArrayException] -> ShowS # | |
Eq ArrayException | Since: base-4.2.0.0 |
Defined in GHC.IO.Exception (==) :: ArrayException -> ArrayException -> Bool # (/=) :: ArrayException -> ArrayException -> Bool # | |
Ord ArrayException | Since: base-4.2.0.0 |
Defined in GHC.IO.Exception compare :: ArrayException -> ArrayException -> Ordering # (<) :: ArrayException -> ArrayException -> Bool # (<=) :: ArrayException -> ArrayException -> Bool # (>) :: ArrayException -> ArrayException -> Bool # (>=) :: ArrayException -> ArrayException -> Bool # max :: ArrayException -> ArrayException -> ArrayException # min :: ArrayException -> ArrayException -> ArrayException # |
data AllocationLimitExceeded #
This thread has exceeded its allocation limit. See
setAllocationCounter
and
enableAllocationLimit
.
Since: base-4.8.0.0
Instances
Exception AllocationLimitExceeded | Since: base-4.8.0.0 |
Show AllocationLimitExceeded | Since: base-4.7.1.0 |
Defined in GHC.IO.Exception showsPrec :: Int -> AllocationLimitExceeded -> ShowS # show :: AllocationLimitExceeded -> String # showList :: [AllocationLimitExceeded] -> ShowS # |
asyncExceptionToException :: Exception e => e -> SomeException #
Since: base-4.7.0.0
asyncExceptionFromException :: Exception e => SomeException -> Maybe e #
Since: base-4.7.0.0
data MaskingState #
Describes the behaviour of a thread when an asynchronous exception is received.
Unmasked | asynchronous exceptions are unmasked (the normal state) |
MaskedInterruptible | the state during |
MaskedUninterruptible | the state during |
Instances
Show MaskingState | Since: base-4.3.0.0 |
Defined in GHC.IO showsPrec :: Int -> MaskingState -> ShowS # show :: MaskingState -> String # showList :: [MaskingState] -> ShowS # | |
Eq MaskingState | Since: base-4.3.0.0 |
Defined in GHC.IO (==) :: MaskingState -> MaskingState -> Bool # (/=) :: MaskingState -> MaskingState -> Bool # |
uninterruptibleMask_ :: IO a -> IO a #
Like uninterruptibleMask
, but does not pass a restore
action
to the argument.
uninterruptibleMask :: ((forall a. IO a -> IO a) -> IO b) -> IO b #
Like mask
, but the masked computation is not interruptible (see
Control.Exception). THIS SHOULD BE USED WITH
GREAT CARE, because if a thread executing in uninterruptibleMask
blocks for any reason, then the thread (and possibly the program,
if this is the main thread) will be unresponsive and unkillable.
This function should only be necessary if you need to mask
exceptions around an interruptible operation, and you can guarantee
that the interruptible operation will only block for a short period
of time.
mask :: ((forall a. IO a -> IO a) -> IO b) -> IO b #
Executes an IO computation with asynchronous
exceptions masked. That is, any thread which attempts to raise
an exception in the current thread with throwTo
will be blocked until asynchronous exceptions are unmasked again.
The argument passed to mask
is a function that takes as its
argument another function, which can be used to restore the
prevailing masking state within the context of the masked
computation. For example, a common way to use mask
is to protect
the acquisition of a resource:
mask $ \restore -> do x <- acquire restore (do_something_with x) `onException` release release
This code guarantees that acquire
is paired with release
, by masking
asynchronous exceptions for the critical parts. (Rather than write
this code yourself, it would be better to use
bracket
which abstracts the general pattern).
Note that the restore
action passed to the argument to mask
does not necessarily unmask asynchronous exceptions, it just
restores the masking state to that of the enclosing context. Thus
if asynchronous exceptions are already masked, mask
cannot be used
to unmask exceptions again. This is so that if you call a library function
with exceptions masked, you can be sure that the library call will not be
able to unmask exceptions again. If you are writing library code and need
to use asynchronous exceptions, the only way is to create a new thread;
see forkIOWithUnmask
.
Asynchronous exceptions may still be received while in the masked state if the masked thread blocks in certain ways; see Control.Exception.
Threads created by forkIO
inherit the
MaskingState
from the parent; that is, to start a thread in the
MaskedInterruptible
state,
use mask_ $ forkIO ...
. This is particularly useful if you need
to establish an exception handler in the forked thread before any
asynchronous exceptions are received. To create a new thread in
an unmasked state use forkIOWithUnmask
.
interruptible :: IO a -> IO a #
Allow asynchronous exceptions to be raised even inside mask
, making
the operation interruptible (see the discussion of "Interruptible operations"
in Exception
).
When called outside mask
, or inside uninterruptibleMask
, this
function has no effect.
Since: base-4.9.0.0
getMaskingState :: IO MaskingState #
Returns the MaskingState
for the current thread.
data IOException #
Exceptions that occur in the IO
monad.
An IOException
records a more specific error type, a descriptive
string and maybe the handle that was used when the error was
flagged.
Instances
Exception IOException | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception | |
Show IOException | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception showsPrec :: Int -> IOException -> ShowS # show :: IOException -> String # showList :: [IOException] -> ShowS # | |
Eq IOException | Since: base-4.1.0.0 |
Defined in GHC.IO.Exception (==) :: IOException -> IOException -> Bool # (/=) :: IOException -> IOException -> Bool # |
This is thrown when the user calls error
. The first String
is the
argument given to error
, second String
is the location.
Instances
Exception ErrorCall | Since: base-4.0.0.0 |
Defined in GHC.Exception toException :: ErrorCall -> SomeException # fromException :: SomeException -> Maybe ErrorCall # displayException :: ErrorCall -> String # | |
Show ErrorCall | Since: base-4.0.0.0 |
Eq ErrorCall | Since: base-4.7.0.0 |
Ord ErrorCall | Since: base-4.7.0.0 |
Defined in GHC.Exception |
throw :: forall (r :: RuntimeRep) (a :: TYPE r) e. Exception e => e -> a #
Throw an exception. Exceptions may be thrown from purely
functional code, but may only be caught within the IO
monad.
class (Typeable e, Show e) => Exception e where #
Any type that you wish to throw or catch as an exception must be an
instance of the Exception
class. The simplest case is a new exception
type directly below the root:
data MyException = ThisException | ThatException deriving Show instance Exception MyException
The default method definitions in the Exception
class do what we need
in this case. You can now throw and catch ThisException
and
ThatException
as exceptions:
*Main> throw ThisException `catch` \e -> putStrLn ("Caught " ++ show (e :: MyException)) Caught ThisException
In more complicated examples, you may wish to define a whole hierarchy of exceptions:
--------------------------------------------------------------------- -- Make the root exception type for all the exceptions in a compiler data SomeCompilerException = forall e . Exception e => SomeCompilerException e instance Show SomeCompilerException where show (SomeCompilerException e) = show e instance Exception SomeCompilerException compilerExceptionToException :: Exception e => e -> SomeException compilerExceptionToException = toException . SomeCompilerException compilerExceptionFromException :: Exception e => SomeException -> Maybe e compilerExceptionFromException x = do SomeCompilerException a <- fromException x cast a --------------------------------------------------------------------- -- Make a subhierarchy for exceptions in the frontend of the compiler data SomeFrontendException = forall e . Exception e => SomeFrontendException e instance Show SomeFrontendException where show (SomeFrontendException e) = show e instance Exception SomeFrontendException where toException = compilerExceptionToException fromException = compilerExceptionFromException frontendExceptionToException :: Exception e => e -> SomeException frontendExceptionToException = toException . SomeFrontendException frontendExceptionFromException :: Exception e => SomeException -> Maybe e frontendExceptionFromException x = do SomeFrontendException a <- fromException x cast a --------------------------------------------------------------------- -- Make an exception type for a particular frontend compiler exception data MismatchedParentheses = MismatchedParentheses deriving Show instance Exception MismatchedParentheses where toException = frontendExceptionToException fromException = frontendExceptionFromException
We can now catch a MismatchedParentheses
exception as
MismatchedParentheses
, SomeFrontendException
or
SomeCompilerException
, but not other types, e.g. IOException
:
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: MismatchedParentheses)) Caught MismatchedParentheses *Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: SomeFrontendException)) Caught MismatchedParentheses *Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: SomeCompilerException)) Caught MismatchedParentheses *Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: IOException)) *** Exception: MismatchedParentheses
Nothing
toException :: e -> SomeException #
fromException :: SomeException -> Maybe e #
displayException :: e -> String #
Render this exception value in a human-friendly manner.
Default implementation:
.show
Since: base-4.8.0.0
Instances
data ArithException #
Arithmetic exceptions.
Overflow | |
Underflow | |
LossOfPrecision | |
DivideByZero | |
Denormal | |
RatioZeroDenominator | Since: base-4.6.0.0 |
Instances
Exception ArithException | Since: base-4.0.0.0 |
Defined in GHC.Exception.Type | |
Show ArithException | Since: base-4.0.0.0 |
Defined in GHC.Exception.Type showsPrec :: Int -> ArithException -> ShowS # show :: ArithException -> String # showList :: [ArithException] -> ShowS # | |
Eq ArithException | Since: base-3.0 |
Defined in GHC.Exception.Type (==) :: ArithException -> ArithException -> Bool # (/=) :: ArithException -> ArithException -> Bool # | |
Ord ArithException | Since: base-3.0 |
Defined in GHC.Exception.Type compare :: ArithException -> ArithException -> Ordering # (<) :: ArithException -> ArithException -> Bool # (<=) :: ArithException -> ArithException -> Bool # (>) :: ArithException -> ArithException -> Bool # (>=) :: ArithException -> ArithException -> Bool # max :: ArithException -> ArithException -> ArithException # min :: ArithException -> ArithException -> ArithException # |
data SomeException #
The SomeException
type is the root of the exception type hierarchy.
When an exception of type e
is thrown, behind the scenes it is
encapsulated in a SomeException
.
Exception e => SomeException e |
Instances
Exception SomeException | Since: base-3.0 |
Defined in GHC.Exception.Type | |
Show SomeException | Since: base-3.0 |
Defined in GHC.Exception.Type showsPrec :: Int -> SomeException -> ShowS # show :: SomeException -> String # showList :: [SomeException] -> ShowS # |
:: (MonadPeelIO m, Exception e) | |
=> m a | The computation to run |
-> (e -> m a) | Handler to invoke if an exception is raised |
-> m a |
Generalized version of catch
.
:: (MonadPeelIO m, Exception e) | |
=> (e -> Maybe b) | Predicate to select exceptions |
-> m a | Computation to run |
-> (b -> m a) | Handler |
-> m a |
Generalized version of catchJust
.
handle :: (MonadPeelIO m, Exception e) => (e -> m a) -> m a -> m a Source #
Generalized version of handle
.
handleJust :: (MonadPeelIO m, Exception e) => (e -> Maybe b) -> (b -> m a) -> m a -> m a Source #
Generalized version of handleJust
.
tryJust :: (MonadPeelIO m, Exception e) => (e -> Maybe b) -> m a -> m (Either b a) Source #
Generalized version of tryJust
.
:: MonadPeelIO m | |
=> m a | computation to run first ("acquire resource") |
-> (a -> m b) | computation to run last ("release resource") |
-> (a -> m c) | computation to run in-between |
-> m c |
Generalized version of bracket
. Note, any monadic side
effects in m
of the "release" computation will be discarded; it
is run only for its side effects in IO
.
bracket_ :: MonadPeelIO m => m a -> m b -> m c -> m c Source #
:: MonadPeelIO m | |
=> m a | computation to run first ("acquire resource") |
-> (a -> m b) | computation to run last ("release resource") |
-> (a -> m c) | computation to run in-between |
-> m c |
Generalized version of bracketOnError
.
:: MonadPeelIO m | |
=> m a | computation to run first |
-> m b | computation to run afterward (even if an exception was raised) |
-> m a |
Generalized version of finally
. Note, any monadic side
effects in m
of the "afterward" computation will be discarded.
onException :: MonadPeelIO m => m a -> m b -> m a Source #
Generalized version of onException
.