[range.join.view]

# 25 Ranges library [[ranges]](./#ranges)

## 25.7 Range adaptors [[range.adaptors]](range.adaptors#range.join.view)

### 25.7.14 Join view [[range.join]](range.join#view)

#### 25.7.14.2 Class template join_view [range.join.view]

[🔗](#lib:join_view)

namespace std::ranges {template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") V>requires [view](range.view#concept:view "25.4.5 Views [range.view]")<V> && [input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]")<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]](range.join.iterator "25.7.14.3 Class template join_­view​::​iterator"), class template join_view​::​*iterator*template<bool Const>struct *iterator*; // *exposition only*// [[range.join.sentinel]](range.join.sentinel "25.7.14.4 Class template join_­view​::​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](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")<V>*non-propagating-cache*<remove_cv_t<*InnerRng*>> *inner_*; // *exposition only*, present only// if is_reference_v<*InnerRng*> is falsepublic: join_view() requires [default_initializable](concept.default.init#concept:default_initializable "18.4.12 Concept default_­initializable [concept.default.init]")<V> = default; constexpr explicit join_view(V base); constexpr V base() const & requires [copy_constructible](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_­constructible [concept.copyconstructible]")<V> { return *base_*; }constexpr V base() && { return std::move(*base_*); }constexpr auto begin() {if constexpr ([forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")<V>) {constexpr bool use_const = [*simple-view*](range.utility.helpers#concept:simple-view "25.5.2 Helper concepts [range.utility.helpers]")<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() constrequires [forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")<const V> && is_reference_v<range_reference_t<const V>> &&[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]")<range_reference_t<const V>>{ return *iterator*<true>{*this, ranges::begin(*base_*)}; }constexpr auto end() {if constexpr ([forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")<V> && is_reference_v<*InnerRng*> && [forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")<*InnerRng*> &&[common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]")<V> && [common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]")<*InnerRng*>)return *iterator*<[*simple-view*](range.utility.helpers#concept:simple-view "25.5.2 Helper concepts [range.utility.helpers]")<V>>{*this, ranges::end(*base_*)}; elsereturn *sentinel*<[*simple-view*](range.utility.helpers#concept:simple-view "25.5.2 Helper concepts [range.utility.helpers]")<V>>{*this}; }constexpr auto end() constrequires [forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")<const V> && is_reference_v<range_reference_t<const V>> &&[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]")<range_reference_t<const V>> {if constexpr ([forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")<range_reference_t<const V>> &&[common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]")<const V> &&[common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]")<range_reference_t<const V>>)return *iterator*<true>{*this, ranges::end(*base_*)}; elsereturn *sentinel*<true>{*this}; }}; template<class R>explicit join_view(R&&) -> join_view<views::all_t<R>>;}

[🔗](#lib:join_view,constructor)

`constexpr explicit join_view(V base);
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L6756)

*Effects*: Initializes *base_* with std​::​move(base)[.](#1.sentence-1)