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4457. freestanding for stable_sort, stable_partition and inplace_merge

Section: 26.4 [algorithm.syn] Status: New Submitter: Braden Ganetsky Opened: 2025-11-06 Last modified: 2025-12-18

Priority: Not Prioritized

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Discussion:

Addresses US 157-255

This applies the resolution for US 157-255.

Proposed resolution:

This wording is relative to N5014.

  1. Modify 26.4 [algorithm.syn], as indicated:

    namespace ranges {
  template<random_access_iterator I, sentinel_for<I> S, class Comp = ranges::less,
           class Proj = identity>
    requires sortable<I, Comp, Proj>
    constexpr I stable_sort(I first, S last, Comp comp = {}, Proj proj = {});         // hosted
  template<random_access_range R, class Comp = ranges::less, class Proj = identity>
    requires sortable<iterator_t<R>, Comp, Proj>
    constexpr borrowed_iterator_t<R>
      stable_sort(R&& r, Comp comp = {}, Proj proj = {});                             // hosted

  template<execution-policy Ep, random_access_iterator I, sized_sentinel_for<I> S,
           class Comp = ranges::less, class Proj = identity>
    requires sortable<I, Comp, Proj>
    I stable_sort(Ep&& exec, I first, S last, Comp comp = {},
                  Proj proj = {});                                        // freestanding-deletedhosted
  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>
      stable_sort(Ep&& exec, R&& r, Comp comp = {}, Proj proj = {});      // freestanding-deletedhosted
}

  2. Modify 26.4 [algorithm.syn], as indicated:

    namespace ranges {
  template<bidirectional_iterator I, sentinel_for<I> S, class Proj = identity,
           indirect_unary_predicate<projected<I, Proj>> Pred>
    requires permutable<I>
    constexpr subrange<I> stable_partition(I first, S last, Pred pred,            // hosted
                                           Proj proj = {});
  template<bidirectional_range R, class Proj = identity,
           indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred>
    requires permutable<iterator_t<R>>
    constexpr borrowed_subrange_t<R> stable_partition(R&& r, Pred pred,           // hosted
                                                      Proj proj = {});

  template<execution-policy Ep, random_access_iterator I, sized_sentinel_for<I> S,
           class Proj = identity, indirect_unary_predicate<projected<I, Proj>> Pred>
    requires permutable<I>
    subrange<I>
      stable_partition(Ep&& exec, I first, S last, Pred pred,
                       Proj proj = {});                                   // freestanding-deletedhosted
  template<execution-policy Ep, sized-random-access-range R, class Proj = identity,
           indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred>
    requires permutable<iterator_t<R>>
    borrowed_subrange_t<R>
      stable_partition(Ep&& exec, R&& r, Pred pred, Proj proj = {});      // freestanding-deletedhosted
}

  3. Modify 26.4 [algorithm.syn], as indicated:

    namespace ranges {
  template<bidirectional_iterator I, sentinel_for<I> S, class Comp = ranges::less,
           class Proj = identity>
    requires sortable<I, Comp, Proj>
    constexpr I
      inplace_merge(I first, I middle, S last, Comp comp = {}, Proj proj = {});       // hosted
  template<bidirectional_range R, class Comp = ranges::less, class Proj = identity>
    requires sortable<iterator_t<R>, Comp, Proj>
    constexpr borrowed_iterator_t<R>
      inplace_merge(R&& r, iterator_t<R> middle, Comp comp = {}, Proj proj = {});     // hosted

  template<execution-policy Ep, random_access_iterator I, sized_sentinel_for<I> S,
           class Comp = ranges::less, class Proj = identity>
    requires sortable<I, Comp, Proj>
    I inplace_merge(Ep&& exec, I first, I middle, S last, Comp comp = {},
                    Proj proj = {});                          // freestanding-deletedhosted
  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>
      inplace_merge(Ep&& exec, R&& r, iterator_t<R> middle, Comp comp = {},
                    Proj proj = {});                          // freestanding-deletedhosted
}