Section: 26.6.3.2 [range.single.view] Status: New Submitter: Hewill Kang Opened: 2023-12-31 Last modified: 2024-01-15 04:53:24 UTC
Priority: Not Prioritized
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Discussion:
Although single_view::empty can be synthesized through view_interface, it seems more worthwhile to provide a static empty for it which eliminates the need to pass in an object parameter, guarantees noexcept-ness, and is consistent with the design of empty_view (demo):
#include <ranges>
auto empty = std::views::empty<int>;
static_assert(noexcept(empty.empty()));
static_assert(noexcept(empty.size()));
auto single = std::views::single(0);
static_assert(noexcept(single.empty())); // fire
static_assert(noexcept(single.size()));
Proposed resolution:
This wording is relative to N4971.
Modify 26.6.3.2 [range.single.view] as indicated:
[…]namespace std::ranges { template<move_constructible T> requires is_object_v<T> class single_view : public view_interface<single_view<T>> { […] public: […] constexpr T* begin() noexcept; constexpr const T* begin() const noexcept; constexpr T* end() noexcept; constexpr const T* end() const noexcept; static constexpr bool empty() noexcept; static constexpr size_t size() noexcept; constexpr T* data() noexcept; constexpr const T* data() const noexcept; }; […] }constexpr T* end() noexcept; constexpr const T* end() const noexcept;-5- Effects: Equivalent to: return data() + 1;
static constexpr bool empty() noexcept;-?- Effects: Equivalent to: return false;