-% ------------------------------------------------------------------------------
-% $Id: Exception.lhs,v 1.2 2001/07/03 14:13:32 simonmar Exp $
-%
-% (c) The University of Glasgow, 1998-2000
-%
-
-Exceptions and exception-handling functions.
-
\begin{code}
{-# OPTIONS -fno-implicit-prelude #-}
+-----------------------------------------------------------------------------
+-- |
+-- Module : GHC.Exception
+-- Copyright : (c) The University of Glasgow, 1998-2002
+-- License : see libraries/base/LICENSE
+--
+-- Maintainer : cvs-ghc@haskell.org
+-- Stability : internal
+-- Portability : non-portable (GHC extensions)
+--
+-- Exceptions and exception-handling functions.
+--
+-----------------------------------------------------------------------------
#ifndef __HUGS__
module GHC.Exception
catch :: IO a -> (Exception -> IO a) -> IO a
catch m k = catchException m handler
where handler err@(IOException _) = k err
- handler err@(UserError _) = k err
handler other = throw other
\end{code}
%*********************************************************
\begin{code}
-#ifndef __HUGS__
+-- | 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 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'.
block :: IO a -> IO a
-block (IO io) = IO $ blockAsyncExceptions# io
+-- | 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
+
+#ifndef __HUGS__
+block (IO io) = IO $ blockAsyncExceptions# io
unblock (IO io) = IO $ unblockAsyncExceptions# io
#else
--- Not implemented yet in Hugs.
-block :: IO a -> IO a
-block (IO io) = IO io
-
unblock :: IO a -> IO a
unblock (IO io) = IO io
#endif