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3946. The definition of const_iterator_t should be reworked

Section: 25.2 [ranges.syn] Status: WP Submitter: Christopher Di Bella Opened: 2023-06-13 Last modified: 2023-11-22

Priority: Not Prioritized

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Discussion:

During the reflector discussion of P2836, consensus was reached that const_iterator_t<R> doesn't necessarily provide the same type as decltype(ranges::cbegin(r)), and that it should be changed to the proposed resolution below so that they're consistent.

[Varna 2023-06-14; Move to Ready]

[2023-11-11 Approved at November 2023 meeting in Kona. Status changed: Voting → WP.]

Proposed resolution:

This wording is relative to N4950.

1. Modify 25.2 [ranges.syn], header <ranges> synopsis, as indicated:

   […]
   template<range R>
     using const_iterator_t = decltype(ranges::cbegin(declval<R&>()))const_iterator<iterator_t<R>>; // freestanding
   template<range R>
     using const_sentinel_t = decltype(ranges::cend(declval<R&>()))const_sentinel<sentinel_t<R>>;   // freestanding
   […]