24 Ranges library [ranges]

24.7 Range adaptors [range.adaptors]

24.7.16 Common view [range.common]

24.7.16.2 Class template common_­view [range.common.view]

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: common_view() requires default_­initializable<V> = default; constexpr explicit common_view(V r); constexpr V base() const& requires copy_­constructible<V> { return base_; } constexpr V base() && { return std::move(base_); } constexpr auto begin() { 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() { if constexpr (random_­access_­range<V> && sized_­range<V>) return ranges::begin(base_) + ranges::size(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::size(base_); else return common_iterator<iterator_t<const V>, sentinel_t<const V>>(ranges::end(base_)); } constexpr auto size() requires sized_­range<V> { return ranges::size(base_); } constexpr auto size() const requires sized_­range<const V> { return ranges::size(base_); } }; template<class R> common_view(R&&) -> common_view<views::all_t<R>>; }
constexpr explicit common_view(V base);
Effects: Initializes base_­ with std​::​move(base).