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4012.common_view::begin/end are missing the simple-view check
Section: 25.7.20.2 [range.common.view] Status: WP Submitter: Hewill Kang Opened: 2023-11-11 Last modified: 2024-04-02
Priority: Not Prioritized
View all other issues in [range.common.view].
View all issues with WP status.
Discussion:
common_view::begin/end have exactly the same implementation as their corresponding const versions, which implies that when the underlying V satisfies simple-view, it is sufficient to just provide const-qualified members.
[2024-03-11; Reflector poll]
Set status to Tentatively Ready after six votes in favour during reflector poll.
[Tokyo 2024-03-23; Status changed: Voting → WP.]
Proposed resolution:
This wording is relative to N4964.
Modify 25.7.20.2 [range.common.view] as indicated:
namespace std::ranges {
template<view V>
requires (!common_range<V> && copyable<iterator_t<V>>)
class common_view : public view_interface<common_view<V>> {
private:
V base_ = V(); // exposition only
public:
[…]
constexpr auto begin() requires (!simple-view<V>) {
if constexpr (random_access_range<V> && sized_range<V>)
return ranges::begin(base_);
else
return common_iterator<iterator_t<V>, sentinel_t<V>>(ranges::begin(base_));
}
constexpr auto begin() const requires range<const V> {
if constexpr (random_access_range<const V> && sized_range<const V>)
return ranges::begin(base_);
else
return common_iterator<iterator_t<const V>, sentinel_t<const V>>(ranges::begin(base_));
}
constexpr auto end() requires (!simple-view<V>) {
if constexpr (random_access_range<V> && sized_range<V>)
return ranges::begin(base_) + ranges::distance(base_);
else
return common_iterator<iterator_t<V>, sentinel_t<V>>(ranges::end(base_));
}
constexpr auto end() const requires range<const V> {
if constexpr (random_access_range<const V> && sized_range<const V>)
return ranges::begin(base_) + ranges::distance(base_);
else
return common_iterator<iterator_t<const V>, sentinel_t<const V>>(ranges::end(base_));
}
[…]
};
[…]
}
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