std::ranges::common_view<V>::begin
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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.[edit] Return value
An iterator to the beginning of the underlying view.
[edit] Example
Run this code
#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
[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 4012 | C++20 | non-const overload missed simple-view check | added |