X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Foreign%2FMarshal%2FError.hs;h=ccf514d70d223ee0c1a34ba945f8d9c2db111dc8;hb=41e8fba828acbae1751628af50849f5352b27873;hp=889ab657d708fe8221ba7d7d703eb56c59c1564d;hpb=771f9ba7d06cd1b454d4bf2b133a028887a4d2af;p=ghc-base.git

diff --git a/Foreign/Marshal/Error.hs b/Foreign/Marshal/Error.hs
index 889ab65..ccf514d 100644
--- a/Foreign/Marshal/Error.hs
+++ b/Foreign/Marshal/Error.hs
@@ -1,29 +1,27 @@
-{-# OPTIONS -fno-implicit-prelude #-}
+{-# LANGUAGE CPP, NoImplicitPrelude #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Foreign.Marshal.Error
 -- Copyright   :  (c) The FFI task force 2001
--- License     :  BSD-style (see the file libraries/core/LICENSE)
+-- License     :  BSD-style (see the file libraries/base/LICENSE)
 -- 
 -- Maintainer  :  ffi@haskell.org
 -- Stability   :  provisional
 -- Portability :  portable
 --
--- Marshalling support: Handling of common error conditions
+-- Routines for testing return values and raising a 'userError' exception
+-- in case of values indicating an error state.
 --
 -----------------------------------------------------------------------------
 
 module Foreign.Marshal.Error (
-  -- * Error utilities
-
-  -- |Throw an exception on specific return values
-  --
   throwIf,       -- :: (a -> Bool) -> (a -> String) -> IO a       -> IO a
   throwIf_,      -- :: (a -> Bool) -> (a -> String) -> IO a       -> IO ()
   throwIfNeg,    -- :: (Ord a, Num a) 
-	         -- =>                (a -> String) -> IO a       -> IO a
+                 -- =>                (a -> String) -> IO a       -> IO a
   throwIfNeg_,   -- :: (Ord a, Num a)
-	         -- =>                (a -> String) -> IO a       -> IO ()
+                 -- =>                (a -> String) -> IO a       -> IO ()
   throwIfNull,   -- ::                String        -> IO (Ptr a) -> IO (Ptr a)
 
   -- Discard return value
@@ -34,21 +32,28 @@ module Foreign.Marshal.Error (
 import Foreign.Ptr
 
 #ifdef __GLASGOW_HASKELL__
+#ifdef __HADDOCK__
+import Data.Bool
+import System.IO.Error
+#endif
 import GHC.Base
 import GHC.Num
-import GHC.IOBase
+-- import GHC.IO
+import GHC.IO.Exception
 #endif
 
 -- exported functions
 -- ------------------
 
--- |Guard an 'IO' operation and throw an exception if the result meets the given
--- predicate 
---
--- * the second argument computes an error message from the result of the 'IO'
---   operation
+-- |Execute an 'IO' action, throwing a 'userError' if the predicate yields
+-- 'True' when applied to the result returned by the 'IO' action.
+-- If no exception is raised, return the result of the computation.
 --
-throwIf                 :: (a -> Bool) -> (a -> String) -> IO a -> IO a
+throwIf :: (a -> Bool)  -- ^ error condition on the result of the 'IO' action
+        -> (a -> String) -- ^ computes an error message from erroneous results
+                        -- of the 'IO' action
+        -> IO a         -- ^ the 'IO' action to be executed
+        -> IO a
 throwIf pred msgfct act  = 
   do
     res <- act