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Showing content from https://en.cppreference.com/w/cpp/language/../algorithm/ranges/../../ranges/elements_view.html below:

std::ranges::views::elements, std::ranges::elements_view - cppreference.com

std::ranges::elements_view (1) (since C++20) namespace views { template< std::size_t N > constexpr /* unspecified */ elements = /* unspecified */; } (2) (since C++20)

Call signature

(since C++20)

Helper concepts

(3) (until C++23)
(exposition only*) (since C++23)
(exposition only*) (4) (exposition only*) 1)

Accepts a

view

of tuple-like values, and issues a view with a value type of the

N^th

element of the adapted view's value-type.

3)

Ensures that the elements of the underlying view are tuple-like values

, see tuple-like(since C++23)

4) Ensures that dangling references cannot be returned.

elements_view models the concepts random_access_range, bidirectional_range, forward_range, input_range, common_range, and sized_range when the underlying view V models respective concepts.

[edit] Data members Member Description V base_ the underlying view
(exposition-only member object*) [edit] Member functions constructs a elements_view
(public member function) [edit] returns a copy of the underlying (adapted) view
(public member function) [edit] returns an iterator to the beginning
(public member function) [edit] returns an iterator or a sentinel to the end
(public member function) [edit] returns the number of elements, provided only if the underlying (adapted) range satisfies sized_range
(public member function) [edit] returns the approximate size of the resulting approximately_sized_range
(public member function) [edit] Inherited from std::ranges::view_interface 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] returns a constant iterator to the beginning of the range
(public member function of std::ranges::view_interface<D>) [edit] returns a sentinel for the constant iterator of the range
(public member function of std::ranges::view_interface<D>) [edit] 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<D>) [edit] returns the first element in the derived view, provided if it satisfies forward_range
(public member function of std::ranges::view_interface<D>) [edit] 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] 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] Nested classes the iterator type
(exposition-only member class template*) the sentinel type
(exposition-only member class template*) [edit] Helper templates

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

[edit] Example

#include <iostream>
#include <ranges>
#include <string>
#include <tuple>
#include <vector>
 
int main()
{
    const std::vector<std::tuple<int, char, std::string>> vt
    {
        {1, 'A', "Î±"},
        {2, 'B', "Î²"},
        {3, 'C', "Î³"},
        {4, 'D', "Î´"},
        {5, 'E', "Îµ"},
    };
 
    for (int const e : std::views::elements<0>(vt))
        std::cout << e << ' ';
    std::cout << '\n';
 
    for (char const e : vt | std::views::elements<1>)
        std::cout << e << ' ';
    std::cout << '\n';
 
    for (std::string const& e : std::views::elements<2>(vt))
        std::cout << e << ' ';
    std::cout << '\n';
}

Output:

1 2 3 4 5
A B C D E
Î± Î² Î³ Î´ Îµ

[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 3494 C++20 elements_view was never a borrowed_range it is a borrowed_range
if its underlying view is LWG 3502 C++20 dangling reference could be obtained from elements_view such usage is forbidden [edit] See also

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