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std::ranges::common_view<V>::begin - cppreference.com

From cppreference.com

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:

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

See also

returns an iterator to the end
(public member function) [edit]
returns an iterator to the beginning of a range
(customization point object)[edit]
returns a sentinel indicating the end of a range
(customization point object)[edit]