base-4.0.0.0: Basic libraries Contents Index

Foreign.Marshal.Error Portability portable Stability provisional Maintainer ffi@haskell.org

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

:: => 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 ()

Discard the return value of an IO action

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