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4038. std::text_encoding::aliases_view should have constexpr iterators

Section: 28.4.2.5 [text.encoding.aliases] Status: WP Submitter: Jonathan Wakely Opened: 2024-01-16 Last modified: 2024-04-02

Priority: Not Prioritized

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Discussion:

aliases_view::begin() and aliases_view::end() are constexpr functions, but there is no requirement that you can use the returned iterator and sentinel in constant expressions.

[2024-03-12; Reflector poll]

Set status to Tentatively Ready after seven votes in favour during reflector poll.

[Tokyo 2024-03-23; Status changed: Voting → WP.]

Proposed resolution:

This wording is relative to N4971.

1. Modify 28.4.2.5 [text.encoding.aliases] as indicated:

   struct text_encoding::aliases_view : ranges::view_interface<text_encoding::aliases_view> {
     constexpr implementation-defined begin() const;
     constexpr implementation-defined end() const;
   };
   

   -1- text_encoding::aliases_view models copyable, ranges::view, ranges::random_access_range, and ranges::borrowed_range.

   -2- Both ranges::range_value_t<text_encoding::aliases_view> and ranges::range_reference_t<text_encoding::aliases_view> denote const char*.

   -?- ranges::iterator_t<text_encoding::aliases_view> is a constexpr iterator (24.3.1 [iterator.requirements.general]).