Re: [hub] on the specialized iteration over elements

Am 17.04.26 um 03:27 schrieb Jean-Louis Leroy via Boost:
> It seems to me that 'visit' is useful and legal only in combination
> with 'operator++',
> 'operator--' and the likes of 'std::next', 'std::prev',
> 'std::advance', etc. For example:
>
>      int main() {
>          boost::container::hub<int> h {1, 3, 5, 7, 9};
>          auto first = h.begin();
>          auto middle = std::next(first, h.size() / 2);
>          auto last = h.end();
>          h.visit(first, middle, [](int i){
>              std::print("{} ", i);
>          });
>          std::print(" | ");
>          h.visit(middle, last, [](int i){
>              std::print("{} ", i);
>          });
>      }
>
> (https://godbolt.org/z/1e5E413r8)
>
> Important use cases are divide-and-conquer algorithms and parallelization.
>
> >From here, two things.
>
> If 'visit' is faster than just "ranging over", it probably (?) means
> that we need
> 'hub::advance' etc as well.
>
> But then an integer displacement is always involved, be it 1 or -1.
> Doesn't it suggest
> that 'visit' should take offsets, not iterators? That would take care
> of Andrzej's
> concern. And there is no need for public 'advance' etc members.

You'd probably still want iterator support not (only) offsets as you 
might want to process all elements until or after the element returned 
by e.g. `std::find`

As for `advance`: That sounds like an ADL-enabled `next` similar to `swap`

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