[Haskell-cafe] FFI Newbie: c functions that want pointers to objects

16 Oct 2008

      Hi,

Some functions in C changes data using pointers,
like this example:

void change_int (int *n)
{
   *n ++;
}

What is the proper way to handle that? I
guess I should wrap it like this:

foreign ccall "change_int" change_int
  :: Ptr CInt -> IO ()

Can I use that on a CInt in Haskell code?
Like this obviously wrong code, but that
probably shows what I want:

do
   let myN = 5
   change_int myN

Thanks,
Maurício

Mauricio