[range.zip] # 25 Ranges library [[ranges]](./#ranges) ## 25.7 Range adaptors [[range.adaptors]](range.adaptors#range.zip) ### 25.7.25 Zip view [range.zip] #### [25.7.25.1](#overview) Overview [[range.zip.overview]](range.zip.overview) [1](#overview-1) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11340) zip_view takes any number of views and produces a view of tuples of references to the corresponding elements of the constituent views[.](#overview-1.sentence-1) [2](#overview-2) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11346) The name views::zip denotes a customization point object ([[customization.point.object]](customization.point.object "16.3.3.3.5 Customization Point Object types"))[.](#overview-2.sentence-1) Given a pack of subexpressions Es..., the expression views::zip(Es...) is expression-equivalent to - [(2.1)](#overview-2.1) auto(views::empty>) if Es is an empty pack, - [(2.2)](#overview-2.2) otherwise, zip_view...>(Es...)[.](#overview-2.sentence-2) [*Example [1](#overview-example-1)*: vector v = {1, 2}; list l = {'a', 'b', 'c'}; auto z = views::zip(v, l); range_reference_t f = z.front(); // f is a tuple// that refers to the first element of v and lfor (auto&& [x, y] : z) { cout << '(' << x << ", " << y << ") "; // prints (1, a) (2, b)} â *end example*] #### [25.7.25.2](#view) Class template zip_view [[range.zip.view]](range.zip.view) [ð](#lib:zip_view_) namespace std::ranges {templateconcept [*zip-is-common*](#concept:zip-is-common "25.7.25.2 Class template zip_view [range.zip.view]") = // *exposition only*(sizeof...(Rs) == 1 && ([common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]") && ...)) ||(!([bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]") && ...) && ([common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]") && ...)) ||(([random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]") && ...) && ([sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]") && ...)); template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]")... Views>requires ([view](range.view#concept:view "25.4.5 Views [range.view]") && ...) && (sizeof...(Views) > 0)class zip_view : public view_interface> { tuple *views_*; // *exposition only*// [[range.zip.iterator]](#iterator "25.7.25.3 Class template zip_view::iterator"), class template zip_view::*iterator*template class *iterator*; // *exposition only*// [[range.zip.sentinel]](#sentinel "25.7.25.4 Class template zip_view::sentinel"), class template zip_view::*sentinel*template class *sentinel*; // *exposition only*public: zip_view() = default; constexpr explicit zip_view(Views... views); constexpr auto begin() requires (!([*simple-view*](range.utility.helpers#concept:simple-view "25.5.2 Helper concepts [range.utility.helpers]") && ...)) {return *iterator*(*tuple-transform*(ranges::begin, *views_*)); }constexpr auto begin() const requires ([range](range.range#concept:range "25.4.2 Ranges [range.range]") && ...) {return *iterator*(*tuple-transform*(ranges::begin, *views_*)); }constexpr auto end() requires (!([*simple-view*](range.utility.helpers#concept:simple-view "25.5.2 Helper concepts [range.utility.helpers]") && ...)) {if constexpr (![*zip-is-common*](#concept:zip-is-common "25.7.25.2 Class template zip_view [range.zip.view]")) {return *sentinel*(*tuple-transform*(ranges::end, *views_*)); } else if constexpr (([random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]") && ...)) {return begin() + iter_difference_t<*iterator*>(size()); } else {return *iterator*(*tuple-transform*(ranges::end, *views_*)); }}constexpr auto end() const requires ([range](range.range#concept:range "25.4.2 Ranges [range.range]") && ...) {if constexpr (![*zip-is-common*](#concept:zip-is-common "25.7.25.2 Class template zip_view [range.zip.view]")) {return *sentinel*(*tuple-transform*(ranges::end, *views_*)); } else if constexpr (([random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]") && ...)) {return begin() + iter_difference_t<*iterator*>(size()); } else {return *iterator*(*tuple-transform*(ranges::end, *views_*)); }}constexpr auto size() requires ([sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]") && ...); constexpr auto size() const requires ([sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]") && ...); }; template zip_view(Rs&&...) -> zip_view...>;} [1](#view-1) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11439) Two zip_view objects have the same underlying sequence if and only if the corresponding elements of *views_* are equal ([[concepts.equality]](concepts.equality "18.2 Equality preservation")) and have the same underlying sequence[.](#view-1.sentence-1) [*Note [1](#view-note-1)*: In particular, comparison of iterators obtained from zip_view objects that do not have the same underlying sequence is not required to produce meaningful results ([[iterator.concept.forward]](iterator.concept.forward "24.3.4.11 Concept forward_iterator"))[.](#view-1.sentence-2) â *end note*] [ð](#lib:zip_view,constructor) `constexpr explicit zip_view(Views... views); ` [2](#view-2) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11455) *Effects*: Initializes *views_* with std::move(views)...[.](#view-2.sentence-1) [ð](#lib:size,zip_view) `constexpr auto size() requires ([sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]") && ...); constexpr auto size() const requires ([sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]") && ...); ` [3](#view-3) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11467) *Effects*: Equivalent to:return apply([](auto... sizes) {using CT = *make-unsigned-like-t*>; return ranges::min({CT(sizes)...});}, *tuple-transform*(ranges::size, *views_*)); #### [25.7.25.3](#iterator) Class template zip_view::*iterator* [[range.zip.iterator]](range.zip.iterator) [ð](#lib:zip_view::iterator) namespace std::ranges {template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]")... Views>requires ([view](range.view#concept:view "25.4.5 Views [range.view]") && ...) && (sizeof...(Views) > 0)templateclass zip_view::*iterator* { tuple>...> *current_*; // *exposition only*constexpr explicit *iterator*(tuple>...>); // *exposition only*public:using iterator_category = input_iterator_tag; // not always presentusing iterator_concept = *see below*; using value_type = tuple>...>; using difference_type = common_type_t>...>; *iterator*() = default; constexpr *iterator*(*iterator* i)requires Const && ([convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_to [concept.convertible]"), iterator_t> && ...); constexpr auto operator*() const; constexpr *iterator*& operator++(); constexpr void operator++(int); constexpr *iterator* operator++(int) requires [*all-forward*](range.adaptor.helpers#concept:all-forward "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); constexpr *iterator*& operator--() requires [*all-bidirectional*](range.adaptor.helpers#concept:all-bidirectional "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); constexpr *iterator* operator--(int) requires [*all-bidirectional*](range.adaptor.helpers#concept:all-bidirectional "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); constexpr *iterator*& operator+=(difference_type x)requires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); constexpr *iterator*& operator-=(difference_type x)requires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); constexpr auto operator[](difference_type n) constrequires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); friend constexpr bool operator==(const *iterator*& x, const *iterator*& y)requires ([equality_comparable](concept.equalitycomparable#concept:equality_comparable "18.5.4 Concept equality_comparable [concept.equalitycomparable]")>> && ...); friend constexpr auto operator<=>(const *iterator*& x, const *iterator*& y)requires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); friend constexpr *iterator* operator+(const *iterator*& i, difference_type n)requires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); friend constexpr *iterator* operator+(difference_type n, const *iterator*& i)requires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); friend constexpr *iterator* operator-(const *iterator*& i, difference_type n)requires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); friend constexpr difference_type operator-(const *iterator*& x, const *iterator*& y)requires ([sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")>, iterator_t<*maybe-const*>> && ...); friend constexpr auto iter_move(const *iterator*& i) noexcept(*see below*); friend constexpr void iter_swap(const *iterator*& l, const *iterator*& r) noexcept(*see below*)requires ([indirectly_swappable](alg.req.ind.swap#concept:indirectly_swappable "24.3.7.4 Concept indirectly_swappable [alg.req.ind.swap]")>> && ...); };} [1](#iterator-1) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11540) *iterator*::iterator_concept is defined as follows: - [(1.1)](#iterator-1.1) If [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]") is modeled, then iterator_concept denotes random_access_iterator_tag[.](#iterator-1.1.sentence-1) - [(1.2)](#iterator-1.2) Otherwise, if [*all-bidirectional*](range.adaptor.helpers#concept:all-bidirectional "25.7.5 Range adaptor helpers [range.adaptor.helpers]") is modeled, then iterator_concept denotes bidirectional_iterator_tag[.](#iterator-1.2.sentence-1) - [(1.3)](#iterator-1.3) Otherwise, if [*all-forward*](range.adaptor.helpers#concept:all-forward "25.7.5 Range adaptor helpers [range.adaptor.helpers]") is modeled, then iterator_concept denotes forward_iterator_tag[.](#iterator-1.3.sentence-1) - [(1.4)](#iterator-1.4) Otherwise, iterator_concept denotes input_iterator_tag[.](#iterator-1.4.sentence-1) [2](#iterator-2) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11558) *iterator*::iterator_category is present if and only if [*all-forward*](range.adaptor.helpers#concept:all-forward "25.7.5 Range adaptor helpers [range.adaptor.helpers]") is modeled[.](#iterator-2.sentence-1) [3](#iterator-3) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11562) If the invocation of any non-const member function of *iterator* exits via an exception, the iterator acquires a singular value[.](#iterator-3.sentence-1) [ð](#lib:zip_view::iterator,constructor) `constexpr explicit iterator(tuple>...> current); ` [4](#iterator-4) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11573) *Effects*: Initializes *current_* with std::move(current)[.](#iterator-4.sentence-1) [ð](#lib:zip_view::iterator,constructor_) `constexpr iterator(iterator i) requires Const && ([convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_to [concept.convertible]"), iterator_t> && ...); ` [5](#iterator-5) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11585) *Effects*: Initializes *current_* with std::move(i.*current_*)[.](#iterator-5.sentence-1) [ð](#lib:operator*,izip_view::iterator) `constexpr auto operator*() const; ` [6](#iterator-6) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11596) *Effects*: Equivalent to:return *tuple-transform*([](auto& i) -> decltype(auto) { return *i; }, *current_*); [ð](#lib:operator++,izip_view::iterator) `constexpr iterator& operator++(); ` [7](#iterator-7) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11610) *Effects*: Equivalent to:*tuple-for-each*([](auto& i) { ++i; }, *current_*);return *this; [ð](#lib:operator++,izip_view::iterator_) `constexpr void operator++(int); ` [8](#iterator-8) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11625) *Effects*: Equivalent to ++*this[.](#iterator-8.sentence-1) [ð](#lib:operator++,izip_view::iterator__) `constexpr iterator operator++(int) requires [all-forward](range.adaptor.helpers#concept:all-forward "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); ` [9](#iterator-9) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11636) *Effects*: Equivalent to:auto tmp = *this;++*this;return tmp; [ð](#lib:operator--,izip_view::iterator) `constexpr iterator& operator--() requires [all-bidirectional](range.adaptor.helpers#concept:all-bidirectional "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); ` [10](#iterator-10) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11652) *Effects*: Equivalent to:*tuple-for-each*([](auto& i) { --i; }, *current_*);return *this; [ð](#lib:operator--,izip_view::iterator_) `constexpr iterator operator--(int) requires [all-bidirectional](range.adaptor.helpers#concept:all-bidirectional "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); ` [11](#iterator-11) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11667) *Effects*: Equivalent to:auto tmp = *this;--*this;return tmp; [ð](#lib:operator+=,izip_view::iterator) `constexpr iterator& operator+=(difference_type x) requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); ` [12](#iterator-12) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11684) *Effects*: Equivalent to:*tuple-for-each*([&](I& i) { i += iter_difference_t(x); }, *current_*);return *this; [ð](#lib:operator-=,izip_view::iterator) `constexpr iterator& operator-=(difference_type x) requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); ` [13](#iterator-13) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11700) *Effects*: Equivalent to:*tuple-for-each*([&](I& i) { i -= iter_difference_t(x); }, *current_*);return *this; [ð](#lib:operator%5b%5d,izip_view::iterator) `constexpr auto operator[](difference_type n) const requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); ` [14](#iterator-14) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11716) *Effects*: Equivalent to:return *tuple-transform*([&](I& i) -> decltype(auto) {return i[iter_difference_t(n)];}, *current_*); [ð](#lib:operator==,izip_view::iterator) `friend constexpr bool operator==(const iterator& x, const iterator& y) requires ([equality_comparable](concept.equalitycomparable#concept:equality_comparable "18.5.4 Concept equality_comparable [concept.equalitycomparable]")>> && ...); ` [15](#iterator-15) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11733) *Returns*: - [(15.1)](#iterator-15.1) x.*current_* == y.*current_* if [*all-bidirectional*](range.adaptor.helpers#concept:all-bidirectional "25.7.5 Range adaptor helpers [range.adaptor.helpers]") is true[.](#iterator-15.1.sentence-1) - [(15.2)](#iterator-15.2) Otherwise, true if there exists an integer 0â¤i(x.*current_*) == std::get(y.*current_*)) is true[.](#iterator-15.2.sentence-1) [*Note [1](#iterator-note-1)*: This allows zip_view to model [common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]") when all constituent views model [common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]")[.](#iterator-15.2.sentence-2) â *end note*] - [(15.3)](#iterator-15.3) Otherwise, false[.](#iterator-15.3.sentence-1) [ð](#lib:operator%3c=%3e,izip_view::iterator) `friend constexpr auto operator<=>(const iterator& x, const iterator& y) requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); ` [16](#iterator-16) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11760) *Returns*: x.*current_* <=> y.*current_*[.](#iterator-16.sentence-1) [ð](#lib:operator+,izip_view::iterator) `friend constexpr iterator operator+(const iterator& i, difference_type n) requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); friend constexpr iterator operator+(difference_type n, const iterator& i) requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); ` [17](#iterator-17) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11774) *Effects*: Equivalent to:auto r = i; r += n;return r; [ð](#lib:operator-,izip_view::iterator) `friend constexpr iterator operator-(const iterator& i, difference_type n) requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]"); ` [18](#iterator-18) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11791) *Effects*: Equivalent to:auto r = i; r -= n;return r; [ð](#lib:operator-,izip_view::iterator_) `friend constexpr difference_type operator-(const iterator& x, const iterator& y) requires ([sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")>, iterator_t>> && ...); ` [19](#iterator-19) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11809) Let *DIST*(i) be difference_type(std::get(x.*current_*) - std::get(y.*current_*))[.](#iterator-19.sentence-1) [20](#iterator-20) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11812) *Returns*: The value with the smallest absolute value among *DIST*(n) for all integers 0â¤n>&>())) && ...) &&(is_nothrow_move_constructible_v>> && ...) [ð](#lib:iter_swap,izip_view::iterator) `friend constexpr void iter_swap(const iterator& l, const iterator& r) noexcept(see below) requires ([indirectly_swappable](alg.req.ind.swap#concept:indirectly_swappable "24.3.7.4 Concept indirectly_swappable [alg.req.ind.swap]")>> && ...); ` [23](#iterator-23) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11849) *Effects*: For every integer 0â¤i(l.*current_*), std::get(r.*current_*)) [24](#iterator-24) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11857) *Remarks*: The exception specification is equivalent to the logical and of the following expressions:noexcept(ranges::iter_swap(std::get(l.*current_*), std::get(r.*current_*))) for every integer 0â¤irequires ([view](range.view#concept:view "25.4.5 Views [range.view]") && ...) && (sizeof...(Views) > 0)templateclass zip_view::*sentinel* { tuple>...> *end_*; // *exposition only*constexpr explicit *sentinel*(tuple>...> end); // *exposition only*public:*sentinel*() = default; constexpr *sentinel*(*sentinel* i)requires Const && ([convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_to [concept.convertible]"), sentinel_t> && ...); templaterequires ([sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")>, iterator_t<*maybe-const*>> && ...)friend constexpr bool operator==(const *iterator*& x, const *sentinel*& y); templaterequires ([sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")>, iterator_t<*maybe-const*>> && ...)friend constexpr common_type_t>...>operator-(const *iterator*& x, const *sentinel*& y); templaterequires ([sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")>, iterator_t<*maybe-const*>> && ...)friend constexpr common_type_t>...>operator-(const *sentinel*& y, const *iterator*& x); };} [ð](#lib:zip_view::sentinel,constructor) `constexpr explicit sentinel(tuple>...> end); ` [1](#sentinel-1) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11910) *Effects*: Initializes *end_* with end[.](#sentinel-1.sentence-1) [ð](#lib:zip_view::sentinel,constructor_) `constexpr sentinel(sentinel i) requires Const && ([convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_to [concept.convertible]"), sentinel_t> && ...); ` [2](#sentinel-2) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11922) *Effects*: Initializes *end_* with std::move(i.*end_*)[.](#sentinel-2.sentence-1) [ð](#lib:operator==,zip_view::sentinel) `template requires ([sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")>, iterator_t>> && ...) friend constexpr bool operator==(const iterator& x, const sentinel& y); ` [3](#sentinel-3) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11936) *Returns*: true if there exists an integer 0â¤i(x.*current_*) == std::get(y.*end_*)) is true[.](#sentinel-3.sentence-1) Otherwise, false[.](#sentinel-3.sentence-2) [ð](#lib:operator-,zip_view::sentinel) `template requires ([sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")>, iterator_t>> && ...) friend constexpr common_type_t>...> operator-(const iterator& x, const sentinel& y); ` [4](#sentinel-4) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11954) Let D be the return type[.](#sentinel-4.sentence-1) Let *DIST*(i) beD(std::get(x.*current_*) - std::get(y.*end_*))[.](#sentinel-4.sentence-2) [5](#sentinel-5) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11959) *Returns*: The value with the smallest absolute value among *DIST*(n) for all integers 0â¤n requires ([sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")>, iterator_t>> && ...) friend constexpr common_type_t>...> operator-(const sentinel& y, const iterator& x); ` [6](#sentinel-6) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11975) *Effects*: Equivalent to: return -(x - y);