Re: Negative nth index

["Sebastián Monía" <sebastian@sebasmonia.com>]

Hello,

Stefan Monnier <monnier@iro.umontreal.ca> writes:
>>>>> Should negative index for nth be valid? e.g.
>>>>> (nth -1 '(1 2)) returns 1
>
> [ I'd make it return 2 otherwise you can't use it to return the
>   last element.  ]
>
>>>> What does this do in other Lisps?
>>> In CL, it errors (ditto for nthcdr with negative index).  Same for (nth
>>> '(1 2 3) -1) in Clojure or (list-ref '(1 2 3) -1) in Scheme.

And for this reason I _would not_ expect it to work with negative
numbers in Elisp.

> 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?

This is "modern"? behaviour that I would expect from seq-elt, because it
is the newest, bell and whistles library.

I have a feeling that keeping `nth' more limited for reasons of
tradition is silly, but...it feels right.

Regards,
Seb

-- 
Sebastián Monía
https://site.sebasmonia.com/