Brian Hulley
My other question is what happens if I want to have a function that takes more than one ForeignPtr as argument ie
foreign import ccall duma_test :: Ptr (Window a) -> Ptr (Window a) -> IO ()
test :: ForeignPtr (Window a) -> ForeignPtr (Window a) -> IO () test p q = withForeignPtr p (\p' -> withForeignPtr q $ duma_test p')
Is this the only way to achieve this? It seems a bit long-winded and possibly a bit inefficient...
I use: \begin{code} {-# INLINE with2ForeignPtrs #-} {-# INLINE with3ForeignPtrs #-} with2ForeignPtrs :: ForeignPtr a -> ForeignPtr b -> (Ptr a -> Ptr b -> IO c) -> IO c with2ForeignPtrs f1 f2 m = withForeignPtr f1 (withForeignPtr f2 . m) \end{code} \begin{code} with3ForeignPtrs :: ForeignPtr a -> ForeignPtr b -> ForeignPtr c -> (Ptr a -> Ptr b -> Ptr c -> IO d) -> IO d with3ForeignPtrs f1 f2 f3 m = withForeignPtr f1 (with2ForeignPtrs f2 f3 . m) \end{code}
foreign import ccall duma_init :: IO ()
^^^^ Any relation with duma.sourceforge.net ? ``D.U.M.A. - Detect Unintended Memory Access'' We just used that for hunting down memory leaks in a C library we produced an FFI binding to... Wolfram