25 Ranges library [ranges]

25.7 Range adaptors [range.adaptors]

25.7.14 Join view [range.join]

25.7.14.2 Class template join_view [range.join.view]

namespace std::ranges { template<input_range V> requires view<V> && input_range<range_reference_t<V>> class join_view : public view_interface<join_view<V>> { private: using InnerRng = range_reference_t<V>; // exposition only // [range.join.iterator], class template join_view::iterator template<bool Const> struct iterator; // exposition only // [range.join.sentinel], class template join_view::sentinel template<bool Const> struct sentinel; // exposition only V base_ = V(); // exposition only non-propagating-cache<iterator_t<V>> outer_; // exposition only, present only // when !forward_range<V> non-propagating-cache<remove_cv_t<InnerRng>> inner_; // exposition only, present only // if is_reference_v<InnerRng> is false public: join_view() requires default_initializable<V> = default; constexpr explicit join_view(V base); constexpr V base() const & requires copy_constructible<V> { return base_; } constexpr V base() && { return std::move(base_); } constexpr auto begin() { if constexpr (forward_range<V>) { constexpr bool use_const = simple-view<V> && is_reference_v<InnerRng>; return iterator<use_const>{*this, ranges::begin(base_)}; } else { outer_ = ranges::begin(base_); return iterator<false>{*this}; } } constexpr auto begin() const requires forward_range<const V> && is_reference_v<range_reference_t<const V>> && input_range<range_reference_t<const V>> { return iterator<true>{*this, ranges::begin(base_)}; } constexpr auto end() { if constexpr (forward_range<V> && is_reference_v<InnerRng> && forward_range<InnerRng> && common_range<V> && common_range<InnerRng>) return iterator<simple-view<V>>{*this, ranges::end(base_)}; else return sentinel<simple-view<V>>{*this}; } constexpr auto end() const requires forward_range<const V> && is_reference_v<range_reference_t<const V>> && input_range<range_reference_t<const V>> { if constexpr (forward_range<range_reference_t<const V>> && common_range<const V> && common_range<range_reference_t<const V>>) return iterator<true>{*this, ranges::end(base_)}; else return sentinel<true>{*this}; } }; template<class R> explicit join_view(R&&) -> join_view<views::all_t<R>>; }

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constexpr explicit join_view(V base);

Effects: Initializes base_ with std::move(base).