std::ranges::common_view<V>::begin

constexpr auto begin() requires (!/simple_view/<V>);	(1)	(since C++20)
constexpr auto begin() const requires range<const V>;	(2)	(since C++20)

1) Returns an iterator to the first element of the common_view, that is:

ranges::begin(base_), if both ranges::random_access_range<V> and ranges::sized_range<V> are satisfied,
std::common_iterator<ranges::iterator_t<V>,ranges::sentinel_t<V>>(ranges::begin(base_)) otherwise.

2) Same as (1), but V is const-qualified.

Return value

An iterator to the beginning of the underlying view.

Example

#include <iostream>
#include <numeric>
#include <ranges>
#include <string_view>

int main()
{
    constexpr auto common = std::views::iota(1)
                          | std::views::take(3)
                          | std::views::common
                          ;

    for (int i{}; int e : common)
        std::cout << (i++ ? " + " : "") << e;

    std::cout << " = " << std::accumulate(common.begin(), common.end(), 0) << '\n';
}

Output:

1 + 2 + 3 = 6

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 4012	C++20	non-const overload missed simple-view check	added

end	returns an iterator to the end (public member function)
ranges::begin (C++20)	returns an iterator to the beginning of a range (customization point object)
ranges::end (C++20)	returns a sentinel indicating the end of a range (customization point object)

std::ranges::common_view<V>::begin

Return value

Example

Defect reports

See also