# Pastebin KfZMf1Tg
main = do
  -- Let's read a number from input...
  putStrLn "Enter a nonnegative integer: "
  s <- getLine
  let n = read s :: CInt
  -- use this number with the C function a couple times
  stuff <- createStuff n
  doubleStuff <- createStuff (n * 2)
  -- then finally print the return value of the C function!
  traverse f stuff
  traverse f doubleStuff
  -- note that f does not deallocate its argument
  -- that is done automatically by the GC later
  -- withForeignPtr is used to "downgrade" ForeignPtr to a Ptr
  where
    f fPtr = withForeignPtr fPtr
             (\p -> do
                 -- convert a C char* to a
                 -- Haskell String
                 xs <- peekCString p
                 putStrLn xs)