std::ranges::views::adjacent,std::ranges::adjacent_view,std::ranges::views::pairwise

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Ranges library

Range access

begin
cbegin
end
cend

rbegin
crbegin
rend
crend

size
ssize
data
cdata

reserve_hint (C++26)
empty

Range conversions
std::from_range_t std::from_range (C++23)(C++23)
to (C++23)

Dangling iterator handling
dangling
borrowed_iterator_t
borrowed_subrange_t

Range primitives

range_size_trange_difference_trange_value_t
elements_of (C++23)

iterator_tconst_iterator_tsentinel_tconst_sentinel_t

(C++23)(C++23)

range_reference_trange_const_reference_trange_rvalue_reference_trange_common_reference_t

(C++23)

Range concepts

range
borrowed_range
common_range

sized_range
viewable_range
view

input_range
output_range
forward_range

bidirectional_range
random_access_range
contiguous_range

approximately_sized_range (C++26)
constant_range (C++23)

empty_viewviews::empty

single_viewviews::single

basic_istream_viewviews::istream

iota_viewviews::iota

repeat_viewviews::repeat

(C++23)(C++23)

Range adaptors

views::all_tviews::all
as_rvalue_viewviews::as_rvalue (C++23)(C++23)
filter_viewviews::filter
transform_viewviews::transform
take_viewviews::take
take_while_viewviews::take_while
common_viewviews::common
views::counted
to_input_viewviews::to_input (C++26)(C++26)

ref_view
drop_viewviews::drop
drop_while_viewviews::drop_while
lazy_split_viewviews::lazy_split
split_viewviews::split
join_viewviews::join
join_with_viewviews::join_with (C++23)(C++23)
concat_viewviews::concat (C++26)(C++26)
cache_latest_viewviews::cache_latest (C++26)(C++26)

owning_view
reverse_viewviews::reverse
as_const_viewviews::as_const (C++23)(C++23)
elements_viewviews::elements
keys_viewviews::keys
values_viewviews::values
enumerate_viewviews::enumerate (C++23)(C++23)
zip_viewviews::zip (C++23)(C++23)
zip_transform_viewviews::zip_transform (C++23)(C++23)

adjacent_viewviews::adjacent (C++23)(C++23)
views::pairwise (C++23)
adjacent_transform_viewviews::adjacent_transform (C++23)(C++23)
views::pairwise_transform (C++23)
chunk_viewviews::chunk (C++23)(C++23)
slide_viewviews::slide (C++23)(C++23)
chunk_by_viewviews::chunk_by (C++23)(C++23)
stride_viewviews::stride (C++23)(C++23)
cartesian_product_viewviews::cartesian_product (C++23)(C++23)

Range generators
std::generator (C++23)

Range adaptor closure objects
range_adaptor_closure (C++23)

Range adaptor objects

Helper items

copyable-box
movable-box

(until C++23) (C++23)

simple-view
non-propagating-cache

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std::ranges::adjacent_view

Member functions
adjacent_view::adjacent_view
adjacent_view::begin
adjacent_view::end
adjacent_view::size
adjacent_view::reserve_hint (C++26)
Iterator
Member functions
adjacent_view::iterator::iterator
adjacent_view::iterator::operator*
adjacent_view::iterator::operator[]
adjacent_view::iterator::operator++ adjacent_view::iterator::operator++(int) adjacent_view::iterator::operator-- adjacent_view::iterator::operator--(int) adjacent_view::iterator::operator+= adjacent_view::iterator::operator-=
Non-member functions
operator==(adjacent_view::iterator) operator<(adjacent_view::iterator) operator>(adjacent_view::iterator) operator<=(adjacent_view::iterator) operator>=(adjacent_view::iterator) operator<=>(adjacent_view::iterator)
operator+(adjacent_view::iterator) operator-(adjacent_view::iterator)
iter_move(adjacent_view::iterator)
iter_swap(adjacent_view::iterator)
Sentinel
Member functions
adjacent_view::sentinel::sentinel
Non-member functions
operator==(adjacent_view::iterator,adjacent_view::sentinel)
operator-(adjacent_view::iterator,adjacent_view::sentinel)

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Defined in header`<ranges>`
template<ranges::forward_range V,std::size_t N> requiresranges::view<V>&&(N>0) class adjacent_view :publicranges::view_interface<adjacent_view<V, N>>	(1)	(since C++23)
namespace views{ template<std::size_t N> constexpr/* unspecified / adjacent=/ unspecified */; }	(2)	(since C++23)
namespace views{ inlineconstexprauto pairwise= adjacent<2>; }	(3)	(since C++23)
Call signature
template<ranges::viewable_range R> requires/* see below */ constexprranges::viewauto adjacent<N>( R&& r);		(since C++23)

1)adjacent_view is a range adaptor that takes aview, and produces aview whosei^th element (a “window”) is astd::tuple that holdsN references to the elements[i, i + N - 1] of the original view.

LetS be the size of the original view. Then the size of produced view is:

S- N+1, ifS >= N,
0 otherwise, and the resulting view is empty.

2) The nameviews::adjacent<N> denotes aRangeAdaptorObject. Given a subexpressione and a constant expressionN, the expressionviews::adjacent<N>(e) isexpression-equivalent to

((void)e,auto(views::empty<tuple<>>)) ifN is equal to0 anddecltype((e)) modelsforward_range,
adjacent_view<views::all_t<decltype((e))>, N>(e) otherwise.

3) The nameviews::pairwise denotes aRangeAdaptorObject that behaves exactly asviews::adjacent<2>.

adjacent_view always modelsforward_range, and modelsbidirectional_range,random_access_range, orsized_range if adaptedview type models the corresponding concept.

[edit]Data members

Member	Description
`Vbase_`	the underlying`view` (exposition-only member object*)

[edit]Member functions

(constructor)	constructs a`adjacent_view` (public member function)[edit]
begin	returns an iterator to the beginning (public member function)[edit]
end	returns an iterator or a sentinel to the end (public member function)[edit]
size	returns the number of elements, provided only if the underlying (adapted) range satisfies`sized_range` (public member function)[edit]
reserve_hint (C++26)	returns the approximate size of the resulting`approximately_sized_range` (public member function)[edit]
Inherited fromstd::ranges::view_interface
empty	returns whether the derived view is empty, provided only if it satisfies`sized_range` or`forward_range` (public member function of`std::ranges::view_interface<D>`)[edit]
cbegin (C++23)	returns a constant iterator to the beginning of the range (public member function of`std::ranges::view_interface<D>`)[edit]
cend (C++23)	returns a sentinel for the constant iterator of the range (public member function of`std::ranges::view_interface<D>`)[edit]
operator bool	returns whether the derived view is not empty, provided only ifranges::empty is applicable to it (public member function of`std::ranges::view_interface<D>`)[edit]
front	returns the first element in the derived view, provided if it satisfies`forward_range` (public member function of`std::ranges::view_interface<D>`)[edit]
back	returns the last element in the derived view, provided only if it satisfies`bidirectional_range` and`common_range` (public member function of`std::ranges::view_interface<D>`)[edit]
operator[]	returns the`n`^th element in the derived view, provided only if it satisfies`random_access_range` (public member function of`std::ranges::view_interface<D>`)[edit]

[edit]Deduction guides

(none)

[edit]Nested classes

iterator	the iterator type (exposition-only member class template*)
sentinel	the sentinel type used when`adjacent_view` is not a`common_range` (exposition-only member class template*)

[edit]Helper templates

template<class V, size_t N> constexprboolranges::enable_borrowed_range<adjacent_view<V, N>>= ranges::enable_borrowed_range<V>;		(since C++23)

This specialization ofranges::enable_borrowed_range makesadjacent_view satisfyborrowed_range when the underlying view satisfies it.

[edit]Notes

views::adjacent only accepts forward ranges even whenN is0.

There are similarities betweenranges::adjacent_view andranges::slide_view:

Both create “sliding window” of sizeN.
Both have the same sizeS - N + 1, whereS is the size of an adaptedview such thatS >= N > 0.

The following table shows the differences between these adaptors:

View adaptor	`value_type`	The window size`N`
ranges::adjacent_view	std::tuple	A template parameter
ranges::slide_view	ranges::range	A runtime argument

Feature-test macro	Value	Std	Feature
`__cpp_lib_ranges_zip`	`202110L`	(C++23)	ranges::zip_view, ranges::zip_transform_view, `ranges::adjacent_view`, ranges::adjacent_transform_view

[edit]Example

Run this code

#include <array>#include <format>#include <iostream>#include <ranges>#include <tuple> int main(){constexprstd::array v{1,2,3,4,5,6};std::cout<<"v = [1 2 3 4 5 6]\n"; for(int i{};std::tuple t: v| std::views::adjacent<3>){auto[t0, t1, t2]= t;std::cout<<std::format("e = {:<{}}[{} {} {}]\n","",2* i++, t0, t1, t2);}}

Output:

v = [1 2 3 4 5 6]e = [1 2 3]e =   [2 3 4]e =     [3 4 5]e =       [4 5 6]

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 4098	C++23	views::adjacent<0> used to accept input-only ranges	made rejected

[edit]References

C++23 standard (ISO/IEC 14882:2024):

26.7.25 Adjacent view [range.adjacent]

[edit]See also

ranges::adjacent_transform_viewviews::adjacent_transform (C++23)	a`view` consisting of results of application of a transformation function to adjacent elements of the adapted view (class template)(range adaptor object)[edit]
ranges::slide_viewviews::slide (C++23)	a`view` whose M^th element is a`view` over the M^th through (M + N - 1)^th elements of another`view` (class template)(range adaptor object)[edit]
ranges::chunk_viewviews::chunk (C++23)	a range of`view`s that are`N`-sized non-overlapping successive chunks of the elements of another`view` (class template)(range adaptor object)[edit]
ranges::stride_viewviews::stride (C++23)	a`view` consisting of elements of another`view`, advancing over N elements at a time (class template)(range adaptor object)[edit]