Title
ranges::rotate do not handle sized-but-not-sized-sentinel ranges correctly
Status
wp
Section
[alg.rotate] [partial.sort] [alg.nth.element] [alg.merge]
Submitter
Tomasz Kamiński

Created on 2025-11-03.00:00:00 last changed 1 month ago

Messages

Date: 2025-11-11.10:48:55

Proposed resolution:

This wording is relative to N5014.

  1. Modify [alg.rotate] as indicated:

    template<execution-policy Ep, sized-random-access-range R>
      requires permutable<iterator_t<R>>
      borrowed_subrange_t<R> ranges::rotate(Ep&& exec, R&& r, iterator_t<R> middle);
    
    

    -6- Effects Equivalent to: return ranges::rotate(std::forward<Ep>(exec), ranges::begin(r), middle, ranges::end(r)ranges::begin(r) + ranges::distance(r));

    […]
    template<execution-policy Ep, sized-random-access-range R, sized-random-access-range OutR>
      requires indirectly_copyable<iterator_t<R>, iterator_t<OutR>>
      ranges::rotate_copy_truncated_result<borrowed_iterator_t<R>, borrowed_iterator_t<OutR>>
    	  ranges::rotate_copy(Ep&& exec, R&& r, iterator_t<R> middle, OutR&& result_r);
    

    -18- Effects Equivalent to: return ranges::rotate(std::forward<Ep>(exec), ranges::begin(r), middle, ranges::end(r)ranges::begin(r) + ranges::distance(r), ranges::begin(result_r), ranges::end(result_r)ranges::begin(result_r) + ranges::distance(result_r));

  2. Modify [partial.sort] as indicated:

    template<execution-policy Ep, sized-random-access-range R,
             class Comp = ranges::less, class Proj = identity>
      requires sortable<iterator_t<R>, Comp, Proj>
      borrowed_iterator_t<R>
        ranges::partial_sort(Ep&& exec, R&& r, iterator_t<R> middle, Comp comp = {},
                             Proj proj = {});
    

    -7- Effects Equivalent to: return ranges::partial_sort(std::forward<Ep>(exec), ranges::begin(r), middle, ranges::end(r)ranges::begin(r) + ranges::distance(r), comp, proj);

  3. Modify [alg.nth.element] as indicated:

    template<execution-policy Ep, sized-random-access-range R, class Comp = ranges::less,
             class Proj = identity>
      requires sortable<iterator_t<R>, Comp, Proj>
      borrowed_iterator_t<R>
        ranges::nth_element(Ep&& exec, R&& r, iterator_t<R> nth, Comp comp = {}, Proj proj = {});
    

    -7- Effects Equivalent to: return ranges::nth_element(std::forward<Ep>(exec), ranges::begin(r), nth, ranges::end(r)ranges::begin(r) + ranges::distance(r), comp, proj);

  4. Modify [alg.merge] as indicated:

    template<execution-policy Ep, sized-random-access-range R, class Comp = ranges::less,
             class Proj = identity>
      requires sortable<iterator_t<R>, Comp, Proj>
      borrowed_iterator_t<R>
        ranges::inplace_merge(Ep&& exec, R&& r, iterator_t<R> middle, Comp comp = {},
                              Proj proj = {});
    

    -14- Effects Equivalent to: return ranges::inplace_merge(std::forward<Ep>(exec), ranges::begin(r), middle, ranges::end(r)ranges::begin(r) + ranges::distance(r), comp, proj);

Date: 2025-11-11.10:48:55

[ Kona 2025-11-08; Status changed: Immediate → WP. ]

Date: 2025-11-04.02:56:53

[ Kona 2025-11-03; approved by LWG. Status changed: New → Immediate. ]

Date: 2025-11-03.00:00:00
Addresses US 161-258

These do not handle sized-but-not-sized-sentinel ranges correctly.

History
Date User Action Args
2025-11-11 10:48:55adminsetmessages: + msg15694
2025-11-11 10:48:55adminsetstatus: immediate -> wp
2025-11-04 02:56:53adminsetmessages: + msg15491
2025-11-04 02:56:53adminsetstatus: new -> immediate
2025-11-04 01:08:04adminsetmessages: + msg15483
2025-11-03 00:00:00admincreate