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[range.adjacent]
# 25 Ranges library [[ranges]](./#ranges)
## 25.7 Range adaptors [[range.adaptors]](range.adaptors#range.adjacent)
### 25.7.27 Adjacent view [range.adjacent]
#### [25.7.27.1](#overview) Overview [[range.adjacent.overview]](range.adjacent.overview)
[1](#overview-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12539)
adjacent_view takes a view and
produces a view whose Mth element is
a tuple of references to
the Mth through (M+N−1)th elements of
the original view[.](#overview-1.sentence-1)
If the original view has fewer than N elements, the resulting view is empty[.](#overview-1.sentence-2)
[2](#overview-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12547)
The name views​::​adjacent<N> denotes
a range adaptor object ([[range.adaptor.object]](range.adaptor.object "25.7.2 Range adaptor objects"))[.](#overview-2.sentence-1)
Given a subexpression E and a constant expression N,
the expression views​::​adjacent<N>(E) is expression-equivalent to
- [(2.1)](#overview-2.1)
((void)E, auto(views​::​empty<tuple<>>)) if N is equal to 0 anddecltype((E)) models [forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]"),
- [(2.2)](#overview-2.2)
otherwise, adjacent_view<views​::​all_t<decltype((E))>, N>(E)[.](#overview-2.sentence-2)
[*Example [1](#overview-example-1)*: vector v = {1, 2, 3, 4};
for (auto i : v | views::adjacent<2>) { cout << "(" << std::get<0>(i) << ", " << std::get<1>(i) << ") "; // prints (1, 2) (2, 3) (3, 4)} — *end example*]
[3](#overview-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12572)
Define *REPEAT*(T, N) as a pack of N types,
each of which denotes the same type as T[.](#overview-3.sentence-1)
#### [25.7.27.2](#view) Class template adjacent_view [[range.adjacent.view]](range.adjacent.view)
[🔗](#lib:adjacent_view)
namespace std::ranges {template<[forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") V, size_t N>requires [view](range.view#concept:view "25.4.5 Views [range.view]")<V> && (N > 0)class adjacent_view : public view_interface<adjacent_view<V, N>> { V *base_* = V(); // *exposition only*// [[range.adjacent.iterator]](#iterator "25.7.27.3 Class template adjacent_­view​::​iterator"), class template adjacent_view​::​*iterator*template<bool> class *iterator*; // *exposition only*// [[range.adjacent.sentinel]](#sentinel "25.7.27.4 Class template adjacent_­view​::​sentinel"), class template adjacent_view​::​*sentinel*template<bool> class *sentinel*; // *exposition only*struct *as-sentinel*{}; // *exposition only*public: adjacent_view() requires [default_initializable](concept.default.init#concept:default_initializable "18.4.12 Concept default_­initializable [concept.default.init]")<V> = default; constexpr explicit adjacent_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() requires (![*simple-view*](range.utility.helpers#concept:simple-view "25.5.2 Helper concepts [range.utility.helpers]")<V>) {return *iterator*<false>(ranges::begin(*base_*), ranges::end(*base_*)); }constexpr auto begin() const requires [range](range.range#concept:range "25.4.2 Ranges [range.range]")<const V> {return *iterator*<true>(ranges::begin(*base_*), ranges::end(*base_*)); }constexpr auto end() requires (![*simple-view*](range.utility.helpers#concept:simple-view "25.5.2 Helper concepts [range.utility.helpers]")<V>) {if constexpr ([common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]")<V>) {return *iterator*<false>(*as-sentinel*{}, ranges::begin(*base_*), ranges::end(*base_*)); } else {return *sentinel*<false>(ranges::end(*base_*)); }}constexpr auto end() const requires [range](range.range#concept:range "25.4.2 Ranges [range.range]")<const V> {if constexpr ([common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]")<const V>) {return *iterator*<true>(*as-sentinel*{}, ranges::begin(*base_*), ranges::end(*base_*)); } else {return *sentinel*<true>(ranges::end(*base_*)); }}constexpr auto size() requires [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]")<V>; constexpr auto size() const requires [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]")<const V>; constexpr auto reserve_hint() requires [approximately_sized_range](range.approximately.sized#concept:approximately_sized_range "25.4.3 Approximately sized ranges [range.approximately.sized]")<V>; constexpr auto reserve_hint() const requires [approximately_sized_range](range.approximately.sized#concept:approximately_sized_range "25.4.3 Approximately sized ranges [range.approximately.sized]")<const V>; };}
[🔗](#lib:adjacent_view,constructor)
`constexpr explicit adjacent_view(V base);
`
[1](#view-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12642)
*Effects*: Initializes *base_* with std​::​move(base)[.](#view-1.sentence-1)
[🔗](#lib:size,adjacent_view)
`constexpr auto size() requires [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]")<V>;
constexpr auto size() const requires [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]")<const V>;
`
[2](#view-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12654)
*Effects*: Equivalent to:using ST = decltype(ranges::size(*base_*));using CT = common_type_t<ST, size_t>;auto sz = static_cast<CT>(ranges::size(*base_*));
sz -= std::min<CT>(sz, N - 1);return static_cast<ST>(sz);
[🔗](#lib:reserve_hint,adjacent_view)
`constexpr auto reserve_hint() requires [approximately_sized_range](range.approximately.sized#concept:approximately_sized_range "25.4.3 Approximately sized ranges [range.approximately.sized]")<V>;
constexpr auto reserve_hint() const requires [approximately_sized_range](range.approximately.sized#concept:approximately_sized_range "25.4.3 Approximately sized ranges [range.approximately.sized]")<const V>;
`
[3](#view-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12673)
*Effects*: Equivalent to:using DT = range_difference_t<decltype((*base_*))>;using CT = common_type_t<DT, size_t>;auto sz = static_cast<CT>(ranges::reserve_hint(*base_*));
sz -= std::min<CT>(sz, N - 1);return *to-unsigned-like*(sz);
#### [25.7.27.3](#iterator) Class template adjacent_view​::​*iterator* [[range.adjacent.iterator]](range.adjacent.iterator)
[🔗](#lib:adjacent_view::iterator)
namespace std::ranges {template<[forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") V, size_t N>requires [view](range.view#concept:view "25.4.5 Views [range.view]")<V> && (N > 0)template<bool Const>class adjacent_view<V, N>::*iterator* {using *Base* = *maybe-const*<Const, V>; // *exposition only* array<iterator_t<*Base*>, N> *current_* = array<iterator_t<*Base*>, N>(); // *exposition only*constexpr *iterator*(iterator_t<*Base*> first, sentinel_t<*Base*> last); // *exposition only*constexpr *iterator*(*as-sentinel*, iterator_t<*Base*> first, iterator_t<*Base*> last); // *exposition only*public:using iterator_category = input_iterator_tag; using iterator_concept = *see below*; using value_type = tuple<*REPEAT*(range_value_t<*Base*>, N)...>; using difference_type = range_difference_t<*Base*>; *iterator*() = default; constexpr *iterator*(*iterator*<!Const> i)requires Const && [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<iterator_t<V>, iterator_t<*Base*>>; constexpr auto operator*() const; constexpr *iterator*& operator++(); constexpr *iterator* operator++(int); constexpr *iterator*& operator--() requires [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; constexpr *iterator* operator--(int) requires [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; constexpr *iterator*& operator+=(difference_type x)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; constexpr *iterator*& operator-=(difference_type x)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; constexpr auto operator[](difference_type n) constrequires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr bool operator==(const *iterator*& x, const *iterator*& y); friend constexpr bool operator<(const *iterator*& x, const *iterator*& y)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr bool operator>(const *iterator*& x, const *iterator*& y)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr bool operator<=(const *iterator*& x, const *iterator*& y)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr bool operator>=(const *iterator*& x, const *iterator*& y)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr auto operator<=>(const *iterator*& x, const *iterator*& y)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*> &&[three_way_comparable](cmp.concept#concept:three_way_comparable "17.12.4 Concept three_­way_­comparable [cmp.concept]")<iterator_t<*Base*>>; friend constexpr *iterator* operator+(const *iterator*& i, difference_type n)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr *iterator* operator+(difference_type n, const *iterator*& i)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr *iterator* operator-(const *iterator*& i, difference_type n)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; 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<*Base*>, iterator_t<*Base*>>; 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]")<iterator_t<*Base*>>; };}
[1](#iterator-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12753)
*iterator*​::​iterator_concept is defined as follows:
- [(1.1)](#iterator-1.1)
If *Base* models [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]"),
then iterator_concept denotes random_access_iterator_tag[.](#iterator-1.1.sentence-1)
- [(1.2)](#iterator-1.2)
Otherwise, if *Base* models [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]"),
then iterator_concept denotes bidirectional_iterator_tag[.](#iterator-1.2.sentence-1)
- [(1.3)](#iterator-1.3)
Otherwise, iterator_concept denotes forward_iterator_tag[.](#iterator-1.3.sentence-1)
[2](#iterator-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12766)
If the invocation of any non-const member function of *iterator* exits via an exception, the *iterator* acquires a singular value[.](#iterator-2.sentence-1)
[🔗](#lib:adjacent_view::iterator,constructor)
`constexpr iterator(iterator_t<Base> first, sentinel_t<Base> last);
`
[3](#iterator-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12776)
*Postconditions*: *current_*[0] == first is true, and
for every integer 1≤i<N,*current_*[i] == ranges​::​next(*current_*[i-1], 1, last) is true[.](#iterator-3.sentence-1)
[🔗](#lib:adjacent_view::iterator,constructor_)
`constexpr iterator(as-sentinel, iterator_t<Base> first, iterator_t<Base> last);
`
[4](#iterator-4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12790)
*Postconditions*: If *Base* does not model [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]"),
each element of *current_* is equal to *last*[.](#iterator-4.sentence-1)
Otherwise, *current_*[N-1] == last is true, and
for every integer 0≤i<(N−1),*current_*[i] == ranges​::​prev(*current_*[i+1], 1, first) is true[.](#iterator-4.sentence-2)
[🔗](#lib:adjacent_view::iterator,constructor__)
`constexpr iterator(iterator<!Const> i)
requires Const && [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<iterator_t<V>, iterator_t<Base>>;
`
[5](#iterator-5)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12807)
*Effects*: Initializes each element of *current_* with the corresponding element of i.*current_* as an xvalue[.](#iterator-5.sentence-1)
[🔗](#lib:operator*,adjacent_view::iterator)
`constexpr auto operator*() const;
`
[6](#iterator-6)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12819)
*Effects*: Equivalent to:return *tuple-transform*([](auto& i) -> decltype(auto) { return *i; }, *current_*);
[🔗](#lib:operator++,adjacent_view::iterator)
`constexpr iterator& operator++();
`
[7](#iterator-7)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12833)
*Preconditions*: *current_*.back() is incrementable[.](#iterator-7.sentence-1)
[8](#iterator-8)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12837)
*Postconditions*: Each element of *current_* is equal to ranges​::​next(i),
where i is the value of that element before the call[.](#iterator-8.sentence-1)
[9](#iterator-9)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12842)
*Returns*: *this[.](#iterator-9.sentence-1)
[🔗](#lib:operator++,adjacent_view::iterator_)
`constexpr iterator operator++(int);
`
[10](#iterator-10)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12853)
*Effects*: Equivalent to:auto tmp = *this;++*this;return tmp;
[🔗](#lib:operator--,adjacent_view::iterator)
`constexpr iterator& operator--() requires [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`
[11](#iterator-11)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12869)
*Preconditions*: *current_*.front() is decrementable[.](#iterator-11.sentence-1)
[12](#iterator-12)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12873)
*Postconditions*: Each element of *current_* is equal to ranges​::​prev(i),
where i is the value of that element before the call[.](#iterator-12.sentence-1)
[13](#iterator-13)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12878)
*Returns*: *this[.](#iterator-13.sentence-1)
[🔗](#lib:operator--,adjacent_view::iterator_)
`constexpr iterator operator--(int) requires [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`
[14](#iterator-14)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12889)
*Effects*: Equivalent to:auto tmp = *this;--*this;return tmp;
[🔗](#lib:operator+=,adjacent_view::iterator)
`constexpr iterator& operator+=(difference_type x)
requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`
[15](#iterator-15)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12906)
*Preconditions*: *current_*.back() + x has well-defined behavior[.](#iterator-15.sentence-1)
[16](#iterator-16)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12910)
*Postconditions*: Each element of *current_* is equal to i + x,
where i is the value of that element before the call[.](#iterator-16.sentence-1)
[17](#iterator-17)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12915)
*Returns*: *this[.](#iterator-17.sentence-1)
[🔗](#lib:operator-=,adjacent_view::iterator)
`constexpr iterator& operator-=(difference_type x)
requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`
[18](#iterator-18)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12927)
*Preconditions*: *current_*.front() - x has well-defined behavior[.](#iterator-18.sentence-1)
[19](#iterator-19)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12931)
*Postconditions*: Each element of *current_* is equal to i - x,
where i is the value of that element before the call[.](#iterator-19.sentence-1)
[20](#iterator-20)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12936)
*Returns*: *this[.](#iterator-20.sentence-1)
[🔗](#lib:operator%5b%5d,adjacent_view::iterator)
`constexpr auto operator[](difference_type n) const
requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`
[21](#iterator-21)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12948)
*Effects*: Equivalent to:return *tuple-transform*([&](auto& i) -> decltype(auto) { return i[n]; }, *current_*);
[🔗](#lib:operator==,adjacent_view::iterator)
`friend constexpr bool operator==(const iterator& x, const iterator& y);
`
[22](#iterator-22)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12962)
*Returns*: x.*current_*.back() == y.*current_*.back()[.](#iterator-22.sentence-1)
[🔗](#lib:operator%3c,adjacent_view::iterator)
`friend constexpr bool operator<(const iterator& x, const iterator& y)
requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`
[23](#iterator-23)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12974)
*Returns*: x.*current_*.back() < y.*current_*.back()[.](#iterator-23.sentence-1)
[🔗](#lib:operator%3e,adjacent_view::iterator)
`friend constexpr bool operator>(const iterator& x, const iterator& y)
requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`
[24](#iterator-24)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12986)
*Effects*: Equivalent to: return y < x;
[🔗](#lib:operator%3c=,adjacent_view::iterator)
`friend constexpr bool operator<=(const iterator& x, const iterator& y)
requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`
[25](#iterator-25)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L12998)
*Effects*: Equivalent to: return !(y < x);
[🔗](#lib:operator%3e=,adjacent_view::iterator)
`friend constexpr bool operator>=(const iterator& x, const iterator& y)
requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`
[26](#iterator-26)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13010)
*Effects*: Equivalent to: return !(x < y);
[🔗](#lib:operator%3c=%3e,adjacent_view::iterator)
`friend constexpr auto operator<=>(const iterator& x, const iterator& y)
requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base> &&
[three_way_comparable](cmp.concept#concept:three_way_comparable "17.12.4 Concept three_­way_­comparable [cmp.concept]")<iterator_t<Base>>;
`
[27](#iterator-27)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13023)
*Returns*: x.*current_*.back() <=> y.*current_*.back()[.](#iterator-27.sentence-1)
[🔗](#lib:operator+,adjacent_view::iterator)
`friend constexpr iterator operator+(const iterator& i, difference_type n)
requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
friend constexpr iterator operator+(difference_type n, const iterator& i)
requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`
[28](#iterator-28)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13037)
*Effects*: Equivalent to:auto r = i;
r += n;return r;
[🔗](#lib:operator-,adjacent_view::iterator)
`friend constexpr iterator operator-(const iterator& i, difference_type n)
requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`
[29](#iterator-29)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13054)
*Effects*: Equivalent to:auto r = i;
r -= n;return r;
[🔗](#lib:operator-,adjacent_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<Base>, iterator_t<Base>>;
`
[30](#iterator-30)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13071)
*Effects*: Equivalent to:return x.*current_*.back() - y.*current_*.back();
[🔗](#lib:iter_move,adjacent_view::iterator)
`friend constexpr auto iter_move(const iterator& i) noexcept(see below);
`
[31](#iterator-31)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13083)
*Effects*: Equivalent to:return *tuple-transform*(ranges​::​iter_move, i.*current_*);
[32](#iterator-32)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13088)
*Remarks*: The exception specification is equivalent to:noexcept(ranges::iter_move(declval<const iterator_t<*Base*>&>())) && is_nothrow_move_constructible_v<range_rvalue_reference_t<*Base*>>
[🔗](#lib:iter_swap,adjacent_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]")<iterator_t<Base>>;
`
[33](#iterator-33)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13104)
*Preconditions*: None of the iterators in l.*current_* is equal to
an iterator in r.*current_*[.](#iterator-33.sentence-1)
[34](#iterator-34)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13109)
*Effects*: For every integer 0≤i<N,
performsranges​::​iter_swap(l.*current_*[i], r.*current_*[i])[.](#iterator-34.sentence-1)
[35](#iterator-35)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13115)
*Remarks*: The exception specification is equivalent to:noexcept(ranges::iter_swap(declval<iterator_t<*Base*>>(), declval<iterator_t<*Base*>>()))
#### [25.7.27.4](#sentinel) Class template adjacent_view​::​*sentinel* [[range.adjacent.sentinel]](range.adjacent.sentinel)
[🔗](#lib:adjacent_view::sentinel)
namespace std::ranges {template<[forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") V, size_t N>requires [view](range.view#concept:view "25.4.5 Views [range.view]")<V> && (N > 0)template<bool Const>class adjacent_view<V, N>::*sentinel* {using *Base* = *maybe-const*<Const, V>; // *exposition only* sentinel_t<*Base*> *end_* = sentinel_t<*Base*>(); // *exposition only*constexpr explicit *sentinel*(sentinel_t<*Base*> end); // *exposition only*public:*sentinel*() = default; constexpr *sentinel*(*sentinel*<!Const> i)requires Const && [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<sentinel_t<V>, sentinel_t<*Base*>>; template<bool OtherConst>requires [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<sentinel_t<*Base*>, iterator_t<*maybe-const*<OtherConst, V>>>friend constexpr bool operator==(const *iterator*<OtherConst>& x, const *sentinel*& y); template<bool OtherConst>requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<sentinel_t<*Base*>, iterator_t<*maybe-const*<OtherConst, V>>>friend constexpr range_difference_t<*maybe-const*<OtherConst, V>>operator-(const *iterator*<OtherConst>& x, const *sentinel*& y); template<bool OtherConst>requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<sentinel_t<*Base*>, iterator_t<*maybe-const*<OtherConst, V>>>friend constexpr range_difference_t<*maybe-const*<OtherConst, V>>operator-(const *sentinel*& y, const *iterator*<OtherConst>& x); };}
[🔗](#lib:adjacent_view::sentinel,constructor)
`constexpr explicit sentinel(sentinel_t<Base> end);
`
[1](#sentinel-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13164)
*Effects*: Initializes *end_* with end[.](#sentinel-1.sentence-1)
[🔗](#lib:adjacent_view::sentinel,constructor_)
`constexpr sentinel(sentinel<!Const> i)
requires Const && [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<sentinel_t<V>, sentinel_t<Base>>;
`
[2](#sentinel-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13176)
*Effects*: Initializes *end_* with std​::​move(i.*end_*)[.](#sentinel-2.sentence-1)
[🔗](#lib:operator==,adjacent_view::sentinel)
`template<bool OtherConst>
requires [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<sentinel_t<Base>, iterator_t<maybe-const<OtherConst, V>>>
friend constexpr bool operator==(const iterator<OtherConst>& x, const sentinel& y);
`
[3](#sentinel-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13189)
*Effects*: Equivalent to: return x.*current_*.back() == y.*end_*;
[🔗](#lib:operator-,adjacent_view::sentinel)
`template<bool OtherConst>
requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<sentinel_t<Base>, iterator_t<maybe-const<OtherConst, V>>>
friend constexpr range_difference_t<maybe-const<OtherConst, V>>
operator-(const iterator<OtherConst>& x, const sentinel& y);
`
[4](#sentinel-4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13203)
*Effects*: Equivalent to: return x.*current_*.back() - y.*end_*;
[🔗](#lib:operator-,adjacent_view::sentinel_)
`template<bool OtherConst>
requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<sentinel_t<Base>, iterator_t<maybe-const<OtherConst, V>>>
friend constexpr range_difference_t<maybe-const<OtherConst, V>>
operator-(const sentinel& y, const iterator<OtherConst>& x);
`
[5](#sentinel-5)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L13217)
*Effects*: Equivalent to: return y.*end_* - x.*current_*.back();