Copyright	(c) The FFI task force 2001
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	ffi@haskell.org
Stability	provisional
Portability	portable
Safe Haskell	Trustworthy
Language	Haskell2010

Foreign.Marshal.Error

Description

Routines for testing return values and raising a userError exception in case of values indicating an error state.

Synopsis

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)
void :: IO a -> IO ()

Documentation

throwIf #

Arguments

:: (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

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 () #

Like throwIf, but discarding the result

throwIfNeg :: (Ord a, Num a) => (a -> String) -> IO a -> IO a #

Guards against negative result values

throwIfNeg_ :: (Ord a, Num a) => (a -> String) -> IO a -> IO () #

Like throwIfNeg, but discarding the result

throwIfNull :: String -> IO (Ptr a) -> IO (Ptr a) #

Guards against null pointers

void :: IO a -> IO () #

Deprecated: use void instead

Discard the return value of an IO action