X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Control%2FException.hs;h=1a407809548f6c659329bd9e6522473d89253cad;hb=c1a7d1856f1af6450ae3e04072b9d36960bc2257;hp=ee063de8848df7eee72307c227638eda6cff8722;hpb=2570f264ed329f04017d507250494eb0ab680d64;p=haskell-directory.git

diff --git a/Control/Exception.hs b/Control/Exception.hs
index ee063de..1a40780 100644
--- a/Control/Exception.hs
+++ b/Control/Exception.hs
@@ -11,6 +11,18 @@
 -- This module provides support for raising and catching both built-in
 -- and user-defined exceptions.
 --
+-- In addition to exceptions thrown by 'IO' operations, exceptions may
+-- be thrown by pure code (imprecise exceptions) or by external events
+-- (asynchronous exceptions), but may only be caught in the 'IO' monad.
+-- For more details, see:
+--
+--  * /A semantics for imprecise exceptions/, by Simon Peyton Jones,
+--    Alastair Reid, Tony Hoare, Simon Marlow, Fergus Henderson,
+--    in /PLDI'99/.
+--
+--  * /Asynchronous exceptions in Haskell/, by Simon Marlow, Simon Peyton
+--    Jones, Andy Moran and John Reppy, in /PLDI'01/.
+--
 -----------------------------------------------------------------------------
 
 module Control.Exception (
@@ -140,7 +152,7 @@ import Data.Dynamic
 -- argument.  Otherwise, the result is returned as normal.  For example:
 --
 -- >   catch (openFile f ReadMode) 
--- >       (\e -> hPutStr stderr (\"Couldn\'t open \"++f++\": \" ++ show e))
+-- >       (\e -> hPutStr stderr ("Couldn't open "++f++": " ++ show e))
 --
 -- For catching exceptions in pure (non-'IO') expressions, see the
 -- function 'evaluate'.
@@ -166,11 +178,19 @@ import Data.Dynamic
 -- Also note that the "Prelude" also exports a function called
 -- 'Prelude.catch' with a similar type to 'Control.Exception.catch',
 -- except that the "Prelude" version only catches the IO and user
--- families of exceptions (as required by Haskell 98).  We recommend
--- either hiding the "Prelude" version of
--- 'Prelude.catch' when importing
--- "Control.Exception", or importing
--- "Control.Exception" qualified, to avoid name-clashes.
+-- families of exceptions (as required by Haskell 98).  
+--
+-- We recommend either hiding the "Prelude" version of 'Prelude.catch'
+-- when importing "Control.Exception": 
+--
+-- > import Prelude hiding (catch)
+--
+-- or importing "Control.Exception" qualified, to avoid name-clashes:
+--
+-- > import qualified Control.Exception as C
+--
+-- and then using @C.catch@
+--
 
 catch  	:: IO a 		-- ^ The computation to run
   	-> (Exception -> IO a)	-- ^ Handler to invoke if an exception is raised
@@ -231,7 +251,7 @@ mapException f v = unsafePerformIO (catch (evaluate v)
 -- @('Right' a)@ if no exception was raised, or @('Left' e)@ if an
 -- exception was raised and its value is @e@.
 --
--- >  try a = catch (Right \`liftM\` a) (return . Left)
+-- >  try a = catch (Right `liftM` a) (return . Left)
 --
 -- Note: as with 'catch', it is only polite to use this variant if you intend
 -- to re-throw the exception after performing whatever cleanup is needed.
@@ -352,7 +372,7 @@ userErrors _ = Nothing
 -- The arguments to 'bracket' are in this order so that we can partially apply 
 -- it, e.g.:
 --
--- > withFile name = bracket (openFile name) hClose
+-- > withFile name mode = bracket (openFile name mode) hClose
 --
 bracket 
 	:: IO a		-- ^ computation to run first (\"acquire resource\")
@@ -506,7 +526,8 @@ uncaughtExceptionHandler = unsafePerformIO (newIORef defaultHandler)
           withCString msg $ \cmsg ->
             errorBelch cfmt cmsg
 
-foreign import ccall unsafe errorBelch :: CString -> CString -> IO ()
+foreign import ccall unsafe "RtsMessages.h errorBelch"
+   errorBelch :: CString -> CString -> IO ()
 
 setUncaughtExceptionHandler :: (Exception -> IO ()) -> IO ()
 setUncaughtExceptionHandler = writeIORef uncaughtExceptionHandler