) where
#ifdef __GLASGOW_HASKELL__
-import GHC.Base ( assert )
-import GHC.IOBase
-import GHC.Exception as ExceptionBase hiding (Exception, catch)
+import GHC.IOBase as ExceptionBase hiding ( catch )
+import GHC.Exception hiding ( Exception )
import GHC.Conc ( throwTo, ThreadId )
import Data.IORef ( IORef, newIORef, readIORef, writeIORef )
import Foreign.C.String ( CString, withCString )
-- These imports are so we can define Typeable instances
-- It'd be better to give Typeable instances in the modules themselves
-- but they all have to be compiled before Typeable
-import GHC.IOBase ( IO, MVar, Exception, ArithException, IOException,
- ArrayException, AsyncException, Handle )
+import GHC.IOBase ( IO, MVar, Exception, ArithException, IOException,
+ ArrayException, AsyncException, Handle, block )
import GHC.ST ( ST )
import GHC.STRef ( STRef )
import GHC.Ptr ( Ptr, FunPtr )
import GHC.Stable ( StablePtr, newStablePtr, freeStablePtr,
deRefStablePtr, castStablePtrToPtr,
castPtrToStablePtr )
-import GHC.Exception ( block )
import GHC.Arr ( Array, STArray )
#endif
#ifdef __GLASGOW_HASKELL__
import GHC.Base ( Int, Monad(..), (.), not )
import GHC.Err ( undefined )
-import GHC.Exception ( block, unblock, throw, catchException, catchAny )
-import GHC.IOBase ( IO, IORef, newIORef, readIORef, writeIORef, )
+import GHC.Exception ( throw )
+import GHC.IOBase ( IO, IORef, newIORef, readIORef, writeIORef
+ block, unblock, catchAny )
import GHC.List ( elem, length )
import GHC.Num ( Num(..) )
#else
import GHC.Read ( Read )
import GHC.Enum ( Enum )
#endif
-import GHC.Exception ( catchException, catchAny, throw, block, unblock )
+import GHC.Exception ( throw )
import GHC.Pack ( packCString# )
import GHC.Ptr ( Ptr(..), plusPtr, FunPtr(..) )
import GHC.STRef
-----------------------------------------------------------------------------
-- #hide
-module GHC.Exception
- ( module GHC.Exception,
- throwIO, ioError )
- where
+module GHC.Exception where
import Data.Maybe
import {-# SOURCE #-} Data.Typeable
import GHC.Base
-import GHC.IOBase hiding (Exception)
-import qualified GHC.IOBase
import GHC.Show
\end{code}
fromException = Just
\end{code}
-For now at least, make the monolithic Exception type an instance.
-
-\begin{code}
-instance Exception GHC.IOBase.Exception
-\end{code}
-
%*********************************************************
%* *
-\subsection{Primitive catch and throw}
+\subsection{Primitive throw}
%* *
%*********************************************************
-catchException used to handle the passing around of the state to the
-action and the handler. This turned out to be a bad idea - it meant
-that we had to wrap both arguments in thunks so they could be entered
-as normal (remember IO returns an unboxed pair...).
-
-Now catch# has type
-
- catch# :: IO a -> (b -> IO a) -> IO a
-
-(well almost; the compiler doesn't know about the IO newtype so we
-have to work around that in the definition of catchException below).
-
\begin{code}
-catchException :: Exception e => IO a -> (e -> IO a) -> IO a
-catchException (IO io) handler = IO $ catch# io handler'
- where handler' e = case fromException e of
- Just e' -> unIO (handler e')
- Nothing -> raise# e
-
-catchAny :: IO a -> (forall e . Exception e => e -> IO a) -> IO a
-catchAny (IO io) handler = IO $ catch# io handler'
- where handler' (SomeException e) = unIO (handler e)
-
--- | The 'catch' function establishes a handler that receives any 'IOError'
--- raised in the action protected by 'catch'. An 'IOError' is caught by
--- the most recent handler established by 'catch'. These handlers are
--- not selective: all 'IOError's are caught. Exception propagation
--- must be explicitly provided in a handler by re-raising any unwanted
--- exceptions. For example, in
---
--- > f = catch g (\e -> if IO.isEOFError e then return [] else ioError e)
---
--- the function @f@ returns @[]@ when an end-of-file exception
--- (cf. 'System.IO.Error.isEOFError') occurs in @g@; otherwise, the
--- exception is propagated to the next outer handler.
---
--- When an exception propagates outside the main program, the Haskell
--- system prints the associated 'IOError' value and exits the program.
---
--- Non-I\/O exceptions are not caught by this variant; to catch all
--- exceptions, use 'Control.Exception.catch' from "Control.Exception".
-catch :: IO a -> (IOError -> IO a) -> IO a
-catch m k = catchException m handler
- where handler (IOException err) = k err
- handler other = throw other
-
-- | Throw an exception. Exceptions may be thrown from purely
-- functional code, but may only be caught within the 'IO' monad.
throw :: Exception e => e -> a
throw e = raise# (toException e)
-
--- | A variant of 'throw' that can be used within the 'IO' monad.
---
--- Although 'throwIO' has a type that is an instance of the type of 'throw', the
--- two functions are subtly different:
---
--- > throw e `seq` x ===> throw e
--- > throwIO e `seq` x ===> x
---
--- The first example will cause the exception @e@ to be raised,
--- whereas the second one won\'t. In fact, 'throwIO' will only cause
--- an exception to be raised when it is used within the 'IO' monad.
--- The 'throwIO' variant should be used in preference to 'throw' to
--- raise an exception within the 'IO' monad because it guarantees
--- ordering with respect to other 'IO' operations, whereas 'throw'
--- does not.
-throwIO :: Exception e => e -> IO a
-throwIO e = IO (raiseIO# (toException e))
\end{code}
-
-%*********************************************************
-%* *
-\subsection{Controlling asynchronous exception delivery}
-%* *
-%*********************************************************
-
-\begin{code}
--- | Applying 'block' to a computation will
--- execute that computation with asynchronous exceptions
--- /blocked/. That is, any thread which
--- attempts to raise an exception in the current thread with 'Control.Exception.throwTo' will be
--- blocked until asynchronous exceptions are enabled again. There\'s
--- no need to worry about re-enabling asynchronous exceptions; that is
--- done automatically on exiting the scope of
--- 'block'.
---
--- Threads created by 'Control.Concurrent.forkIO' inherit the blocked
--- state from the parent; that is, to start a thread in blocked mode,
--- use @block $ forkIO ...@. This is particularly useful if you need to
--- establish an exception handler in the forked thread before any
--- asynchronous exceptions are received.
-block :: IO a -> IO a
-
--- | To re-enable asynchronous exceptions inside the scope of
--- 'block', 'unblock' can be
--- used. It scopes in exactly the same way, so on exit from
--- 'unblock' asynchronous exception delivery will
--- be disabled again.
-unblock :: IO a -> IO a
-
-block (IO io) = IO $ blockAsyncExceptions# io
-unblock (IO io) = IO $ unblockAsyncExceptions# io
-
--- | returns True if asynchronous exceptions are blocked in the
--- current thread.
-blocked :: IO Bool
-blocked = IO $ \s -> case asyncExceptionsBlocked# s of
- (# s', i #) -> (# s', i /=# 0# #)
-\end{code}
-
-\begin{code}
--- | Forces its argument to be evaluated when the resultant 'IO' action
--- is executed. It can be used to order evaluation with respect to
--- other 'IO' operations; its semantics are given by
---
--- > evaluate x `seq` y ==> y
--- > evaluate x `catch` f ==> (return $! x) `catch` f
--- > evaluate x >>= f ==> (return $! x) >>= f
---
--- /Note:/ the first equation implies that @(evaluate x)@ is /not/ the
--- same as @(return $! x)@. A correct definition is
---
--- > evaluate x = (return $! x) >>= return
---
-evaluate :: a -> IO a
-evaluate a = IO $ \s -> case a `seq` () of () -> (# s, a #)
- -- NB. can't write
- -- a `seq` (# s, a #)
- -- because we can't have an unboxed tuple as a function argument
-\end{code}
+++ /dev/null
-
-\begin{code}
-{-# OPTIONS_GHC -XNoImplicitPrelude #-}
-
-module GHC.Exception where
-
-import {-# SOURCE #-} qualified GHC.IOBase as IOB
-
-class Exception e
-
-data SomeException
-
-instance Exception IOB.Exception
-
-throwIO :: Exception e => e -> IOB.IO a
-
-toException :: Exception e => e -> SomeException
-\end{code}
-
import GHC.Read ( Read )
import GHC.List
import GHC.IOBase
-import GHC.Exception ( block, catchException, catchAny, throw, throwIO )
+import GHC.Exception ( throw )
import GHC.Enum
import GHC.Num ( Integer(..), Num(..) )
import GHC.Show
import GHC.Num
import GHC.Show
import GHC.List
-import GHC.Exception ( ioError, catch )
#ifdef mingw32_HOST_OS
import GHC.Conc
stackOverflow, heapOverflow, ioException,
IOError, IOException(..), IOErrorType(..), ioError, userError,
ExitCode(..),
+ throwIO, block, unblock, catch, catchAny, catchException,
+ evaluate,
-- The RTS calls this
nonTermination,
) where
import GHC.List
import GHC.Read
import Foreign.C.Types (CInt)
-import {-# SOURCE #-} GHC.Exception ( SomeException, toException, throwIO )
+import GHC.Exception hiding (Exception)
+import qualified GHC.Exception as Exc
#ifndef __HADDOCK__
import {-# SOURCE #-} Data.Typeable ( showsTypeRep )
nonTermination :: SomeException
nonTermination = toException NonTermination
+-- For now at least, make the monolithic Exception type an instance of
+-- the Exception class
+instance Exc.Exception Exception
+
-- |The type of arithmetic exceptions
data ArithException
= Overflow
data IOMode = ReadMode | WriteMode | AppendMode | ReadWriteMode
deriving (Eq, Ord, Ix, Enum, Read, Show)
\end{code}
+
+%*********************************************************
+%* *
+\subsection{Primitive catch and throwIO}
+%* *
+%*********************************************************
+
+catchException used to handle the passing around of the state to the
+action and the handler. This turned out to be a bad idea - it meant
+that we had to wrap both arguments in thunks so they could be entered
+as normal (remember IO returns an unboxed pair...).
+
+Now catch# has type
+
+ catch# :: IO a -> (b -> IO a) -> IO a
+
+(well almost; the compiler doesn't know about the IO newtype so we
+have to work around that in the definition of catchException below).
+
+\begin{code}
+catchException :: Exception e => IO a -> (e -> IO a) -> IO a
+catchException (IO io) handler = IO $ catch# io handler'
+ where handler' e = case fromException e of
+ Just e' -> unIO (handler e')
+ Nothing -> raise# e
+
+catchAny :: IO a -> (forall e . Exception e => e -> IO a) -> IO a
+catchAny (IO io) handler = IO $ catch# io handler'
+ where handler' (SomeException e) = unIO (handler e)
+
+-- | A variant of 'throw' that can be used within the 'IO' monad.
+--
+-- Although 'throwIO' has a type that is an instance of the type of 'throw', the
+-- two functions are subtly different:
+--
+-- > throw e `seq` x ===> throw e
+-- > throwIO e `seq` x ===> x
+--
+-- The first example will cause the exception @e@ to be raised,
+-- whereas the second one won\'t. In fact, 'throwIO' will only cause
+-- an exception to be raised when it is used within the 'IO' monad.
+-- The 'throwIO' variant should be used in preference to 'throw' to
+-- raise an exception within the 'IO' monad because it guarantees
+-- ordering with respect to other 'IO' operations, whereas 'throw'
+-- does not.
+throwIO :: Exception e => e -> IO a
+throwIO e = IO (raiseIO# (toException e))
+\end{code}
+
+
+%*********************************************************
+%* *
+\subsection{Controlling asynchronous exception delivery}
+%* *
+%*********************************************************
+
+\begin{code}
+-- | Applying 'block' to a computation will
+-- execute that computation with asynchronous exceptions
+-- /blocked/. That is, any thread which
+-- attempts to raise an exception in the current thread with 'Control.Exception.throwTo' will be
+-- blocked until asynchronous exceptions are enabled again. There\'s
+-- no need to worry about re-enabling asynchronous exceptions; that is
+-- done automatically on exiting the scope of
+-- 'block'.
+--
+-- Threads created by 'Control.Concurrent.forkIO' inherit the blocked
+-- state from the parent; that is, to start a thread in blocked mode,
+-- use @block $ forkIO ...@. This is particularly useful if you need to
+-- establish an exception handler in the forked thread before any
+-- asynchronous exceptions are received.
+block :: IO a -> IO a
+
+-- | To re-enable asynchronous exceptions inside the scope of
+-- 'block', 'unblock' can be
+-- used. It scopes in exactly the same way, so on exit from
+-- 'unblock' asynchronous exception delivery will
+-- be disabled again.
+unblock :: IO a -> IO a
+
+block (IO io) = IO $ blockAsyncExceptions# io
+unblock (IO io) = IO $ unblockAsyncExceptions# io
+\end{code}
+
+\begin{code}
+-- | Forces its argument to be evaluated when the resultant 'IO' action
+-- is executed. It can be used to order evaluation with respect to
+-- other 'IO' operations; its semantics are given by
+--
+-- > evaluate x `seq` y ==> y
+-- > evaluate x `catch` f ==> (return $! x) `catch` f
+-- > evaluate x >>= f ==> (return $! x) >>= f
+--
+-- /Note:/ the first equation implies that @(evaluate x)@ is /not/ the
+-- same as @(return $! x)@. A correct definition is
+--
+-- > evaluate x = (return $! x) >>= return
+--
+evaluate :: a -> IO a
+evaluate a = IO $ \s -> case a `seq` () of () -> (# s, a #)
+ -- NB. can't write
+ -- a `seq` (# s, a #)
+ -- because we can't have an unboxed tuple as a function argument
+\end{code}
+
module GHC.IOBase where
data Exception
-data IO a
\end{code}
import Foreign
import Foreign.C
import GHC.IOBase
-import GHC.Exception ( catchException )
import GHC.Prim
import GHC.Conc
import GHC.Weak
#endif
#ifdef __GLASGOW_HASKELL__
-import GHC.Exception as ExceptionBase hiding (catch)
+import GHC.IOBase as ExceptionBase
#endif
#ifdef __HUGS__
import Hugs.Exception as ExceptionBase
projects / ghc-base.git / commitdiff