On Mon, 9 Mar 2020 13:31:06 -0000 (UTC)
Martin Gregorie  wrote:

> On Mon, 09 Mar 2020 10:02:00 +0000, Ahem A Rivet's Shot wrote:
>
> > Instead of 'next' the pointer field contains 'next xor previous'
> > provided you know where you came from 'last' you go to 'last xor
> > pointer'
> > to continue in the same direction.
> >
> Very nice!

 Very much mixed feelings - wherever possible use two pointers, when
you can't it's a lifesaver. Now x & -x OTOH - that's just neat (two's
complement machines only).

> I hope it was well commented, though, for the benefit of whoever would
> modify the code next (this included yourself!)

 Oh yes GPFO comment with lots of detail.

> .....
>
> The worst piece of tricksy, undocumented and uncommented code I remember
> seeing was 60 lines (one lineprinter page) of 1900 assembler. It used no
> variables or labels: all data was held in the 8 accumulators and all
> control transfers were relative jumps. The only comment in the entire
> mess was:
>
> Calculate last day in month. Works until Feb 2100.

 Sounds a lot like the source of the BASIC for the Camputer's Lynx
which I was unfortunate enough to see. Sixteen kilobytes of almost
completely uncommented Z80 assembler - the only comments were clearly
reminders for overnight breaks and hopelessly cryptic. It had apparently
been written in six weeks - it looked like it!

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