Re: [PATCH 1/5] lib: add find_nth(,and,andnot)_bit()

[Andy Shevchenko]

On Fri, Jul 8, 2022 at 10:55 AM Rasmus Villemoes
<linux@xxxxxxxxxxxxxxxxxx> wrote:
> On 07/07/2022 23.03, Yury Norov wrote:
>
> >> And I don't
> >> like that the index is apparently 1-based (and that surprising API isn't
> >> spelled out anywhere).
> >
> > Yeah... My motivation to start counting from 1 is to keep consistency
> > with ffs: __ffs(word) <=> fns(word, 1).
>
> I understand that you're translating that second f in ffs (find First
> set) to a 1. But I disagree that that's necessarily a logical thing to
> do. Everybody understands that (given a C or python or... context) when
> some prose talks about "the first element in an array", it's the one at
> [0]. So I find it much more natural that the set bits in a word are
> enumerated 0, 1, ..., popcount(w)-1.

I agree that here we operate with an array of bits, which naturally
starts from bit 0.

-- 
With Best Regards,
Andy Shevchenko