bug#55395: What does (1 2 3 . #2) mean?

[Lars Ingebrigtsen]

Mattias Engdegård <mattiase@acm.org> writes:

> It may have made more sense before the switch of cycle-detection algorithm 
> from Floyd to Brent. This can be fixed by hand-coding the list iteration and 
> explicitly remembering the index of the tortoise, but would that be correct? 
> What's the spec?

I don't think I've ever considered #x to be meaningful outside of
print-circle, but I guess if we wanted to have some semantics here, I
think I would have expected the index of the tortoise?  But...

> If #N means 'Nth object from the top along the path to the current object, 
> starting at 0' then we should have
>
> (rho 2 3) => (1 2 3 4 5 . #2)
> (list (rho 2 3)) => ((1 2 3 4 5 . #3))
>
> ie, adding the print depth to the index in the list. Do you agree?

I've added Stefan to the CCs; I'm sure he has an opinion.

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