33 Foreign.Marshal.Error
Date: 2010-07-20 13:11:00

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## Chapter 33
Foreign.Marshal.Error

module Foreign.Marshal.Error (
throwIf, throwIf_, throwIfNeg, throwIfNeg_, throwIfNull, void
) where

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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