[project @ 2001-07-31 14:34:23 by simonmar]

add a couple of useful variants of catch & catchJust:

	handle	   :: (Exception -> IO a) -> IO a -> IO a
	handleJust :: (Exception -> Maybe b) -> (b -> IO a) -> IO a -> IO a

diff --git a/Control/Exception.hs b/Control/Exception.hs
index 444ac87..041b222 100644 (file)
--- a/Control/Exception.hs
+++ b/Control/Exception.hs
@@ -8,7 +8,7 @@
 -- Stability   :  experimental
 -- Portability :  non-portable
 --
--- $Id: Exception.hs,v 1.1 2001/06/28 14:15:01 simonmar Exp $
+-- $Id: Exception.hs,v 1.2 2001/07/31 14:34:23 simonmar Exp $
 --
 -- The External API for exceptions.  The functions provided in this
 -- module allow catching of exceptions in the IO monad.
@@ -29,9 +29,12 @@ 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
@@ -105,10 +108,10 @@ 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 +119,12 @@ 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