std::ranges::views::adjacent, std::ranges::adjacent_view, std::ranges::views::pairwise - cppreference.com (original) (raw)

std::ranges::adjacent_view

Defined in header
template< ranges::forward_range V, std::size_t N > requires ranges::view<V> && (N > 0) class adjacent_view : public ranges::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 { inline constexpr auto pairwise = adjacent<2>; } (3) (since C++23)
Call signature
template< ranges::viewable_range R > requires /* see below */ constexpr ranges::view auto adjacent<N>( R&& r ); (since C++23)
  1. adjacent_view is a range adaptor that takes a view, and produces a view whose _i_th element (a “window”) is a std::tuple that holds _N_ references to the elements [ _i_ , _i + N - 1_ ] of the original view.

Let _S_ be the size of the original view. Then the size of produced view is:

  1. The name views::pairwise denotes a RangeAdaptorObject that behaves exactly as views::adjacent<2>.

adjacent_view always models forward_range, and models bidirectional_range, random_access_range, or sized_range if adapted view type models the corresponding concept.

Contents

[edit] Data members

Member Description
V base_ 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 from std::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) [edit]
cbegin(C++23) returns a constant iterator to the beginning of the range (public member function of std::ranges::view_interface) [edit]
cend(C++23) returns a sentinel for the constant iterator of the range (public member function of std::ranges::view_interface) [edit]
operator bool returns whether the derived view is not empty, provided only if ranges::empty is applicable to it (public member function of std::ranges::view_interface) [edit]
front returns the first element in the derived view, provided if it satisfies forward_range (public member function of std::ranges::view_interface) [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) [edit]
operator[] returns the nth element in the derived view, provided only if it satisfies random_access_range (public member function of std::ranges::view_interface) [edit]

[edit] Deduction guides

(none)

[edit] Nested classes

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

[edit] Helper templates

This specialization of ranges::enable_borrowed_range makes adjacent_view satisfy borrowed_range when the underlying view satisfies it.

[edit] Notes

views::adjacent only accepts forward ranges even when N is 0.

There are similarities between ranges::adjacent_view and ranges::slide_view:

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

#include #include #include #include #include   int main() { constexpr std::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

[edit] See also