[project @ 2002-05-09 13:16:29 by simonmar]

[ghc-base.git] / Control / Exception.hs

diff --git a/Control/Exception.hs b/Control/Exception.hs
index 444ac87..8a66e97 100644 (file)
--- a/Control/Exception.hs
+++ b/Control/Exception.hs
@@ -1,15 +1,13 @@
 -----------------------------------------------------------------------------
--- 
+-- |
 -- Module      :  Control.Exception
 -- Copyright   :  (c) The University of Glasgow 2001
--- License     :  BSD-style (see the file libraries/core/LICENSE)
+-- License     :  BSD-style (see the file libraries/base/LICENSE)
 -- 
 -- Maintainer  :  libraries@haskell.org
 -- Stability   :  experimental
 -- Portability :  non-portable
 --
--- $Id: Exception.hs,v 1.1 2001/06/28 14:15:01 simonmar Exp $
---
 -- The External API for exceptions.  The functions provided in this
 -- module allow catching of exceptions in the IO monad.
 --
@@ -29,9 +27,12 @@ module Control.Exception (
        catch,     -- :: IO a -> (Exception -> IO a) -> IO a
        catchJust, -- :: (Exception -> Maybe b) -> IO a -> (b -> IO a) -> IO a
 
+       handle,    -- :: (Exception -> IO a) -> IO a -> IO a
+       handleJust,-- :: (Exception -> Maybe b) -> (b -> IO a) -> IO a -> IO a
+
        evaluate,  -- :: a -> IO a
 
-       -- Exception predicates (for catchJust, tryJust)
+       -- Exception predicates (for tryJust, catchJust, handleJust)
 
        ioErrors,               -- :: Exception -> Maybe IOError
        arithExceptions,        -- :: Exception -> Maybe ArithException
@@ -44,10 +45,7 @@ module Control.Exception (
        -- Throwing exceptions
 
        throw,          -- :: Exception -> a
-#ifndef __STGHUGS__
-       -- for now
        throwTo,        -- :: ThreadId -> Exception -> a
-#endif
 
        -- Dynamic exceptions
 
@@ -76,7 +74,8 @@ module Control.Exception (
 
 #ifdef __GLASGOW_HASKELL__
 import Prelude                 hiding (catch)
-import GHC.Prim                ( assert )
+import System.IO.Error
+import GHC.Base                ( assert )
 import GHC.Exception   hiding (try, catch, bracket, bracket_)
 import GHC.Conc                ( throwTo, ThreadId )
 import GHC.IOBase      ( IO(..) )
@@ -105,10 +104,10 @@ INSTANCE_TYPEABLE0(AsyncException,asyncExceptionTc,"AsyncException")
 -----------------------------------------------------------------------------
 -- Catching exceptions
 
--- PrelException defines 'catchException' for us.
+-- GHC.Exception defines 'catchException' for us.
 
-catch :: IO a -> (Exception -> IO a) -> IO a
-catch =  catchException
+catch    :: IO a -> (Exception -> IO a) -> IO a
+catch    =  catchException
 
 catchJust :: (Exception -> Maybe b) -> IO a -> (b -> IO a) -> IO a
 catchJust p a handler = catch a handler'
@@ -116,6 +115,12 @@ catchJust p a handler = catch a handler'
                        Nothing -> throw e
                        Just b  -> handler b
 
+handle    :: (Exception -> IO a) -> IO a -> IO a
+handle     =  flip catch
+
+handleJust :: (Exception -> Maybe b) -> (b -> IO a) -> IO a -> IO a
+handleJust p =  flip (catchJust p)
+
 -----------------------------------------------------------------------------
 -- evaluate
 
@@ -193,7 +198,7 @@ dynExceptions _ = Nothing
 asyncExceptions (AsyncException e) = Just e
 asyncExceptions _ = Nothing
 
-userErrors (UserError e) = Just e
+userErrors e | isUserError e = Just (ioeGetErrorString e)
 userErrors _ = Nothing
 
 -----------------------------------------------------------------------------