Fixed; thanks. I made a couple of changes:

- Use "argument" rather than "arg", to be consistent with the original code (but admittedly not consistent with the rest of the module, where there doesn't seem to be any consistent choice between "arg" and "argument").
- Reformat C and test code to avoid long lines.
- Slight rearrangement of the C code so that all of the "i" handling is in one place.