Re: Negative nth index

[Stefan Monnier <monnier@iro.umontreal.ca>]

> I don't see a strong argument in favor of making it index from the end
> rather than signal an error.  What would the implementation look like?
> Would it be significantly more efficient than doing it "by hand" e.g.:
>
>     (let ((l (length X)))
>       (nth (if (< i 0) (- l i) i) X))

AFAICT so far people were only able to fix my code but not answer my
question, which suggests the answer is no, which would be a good
argument in favor of staying with the current behavior: the change
wouldn't save us from going down the list twice.


        Stefan