/usr/lib/hugs/packages/base/Foreign/Marshal/Error.hs is in libhugs-base-bundled 98.200609.21-5.3ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 | {-# OPTIONS_GHC -fno-implicit-prelude #-}
-----------------------------------------------------------------------------
-- |
-- Module : Foreign.Marshal.Error
-- Copyright : (c) The FFI task force 2001
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : ffi@haskell.org
-- Stability : provisional
-- Portability : portable
--
-- Routines for testing return values and raising a 'userError' exception
-- in case of values indicating an error state.
--
-----------------------------------------------------------------------------
module Foreign.Marshal.Error (
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
throwIfNeg_, -- :: (Ord a, Num a)
-- => (a -> String) -> IO a -> IO ()
throwIfNull, -- :: String -> IO (Ptr a) -> IO (Ptr a)
-- Discard return value
--
void -- IO a -> IO ()
) where
import Foreign.Ptr
-- exported functions
-- ------------------
-- |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) -- ^ 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
(if pred res then ioError . userError . msgfct else return) res
-- |Like 'throwIf', but discarding the result
--
throwIf_ :: (a -> Bool) -> (a -> String) -> IO a -> IO ()
throwIf_ pred msgfct act = void $ throwIf pred msgfct act
-- |Guards against negative result values
--
throwIfNeg :: (Ord a, Num a) => (a -> String) -> IO a -> IO a
throwIfNeg = throwIf (< 0)
-- |Like 'throwIfNeg', but discarding the result
--
throwIfNeg_ :: (Ord a, Num a) => (a -> String) -> IO a -> IO ()
throwIfNeg_ = throwIf_ (< 0)
-- |Guards against null pointers
--
throwIfNull :: String -> IO (Ptr a) -> IO (Ptr a)
throwIfNull = throwIf (== nullPtr) . const
-- |Discard the return value of an 'IO' action
--
void :: IO a -> IO ()
void act = act >> return ()
|