std::ranges::drop_view<V>::size
来自cppreference.com
constexpr auto size() requires ranges::sized_range<V>; |
(1) | (C++20 起) |
constexpr auto size() const requires ranges::sized_range<const V>; |
(2) | (C++20 起) |
返回元素数。
令 base_
为底层视图, count_
为存储的计数(通常为传递给构造函数的数,或若 *this 为默认构造则为 0 )。等价于
const auto s = ranges::size(base_); const auto c = static_cast<decltype(s)>(count_); return s < c ? 0 : s - c;
参数
(无)
返回值
元素数。
示例
运行此代码
#include <array> #include <ranges> int main() { constexpr std::array a{42, 43, 44}; static_assert(std::ranges::drop_view{std::views::all(a), 0}.size() == 3); static_assert(std::ranges::drop_view{std::views::all(a), 1}.size() == 2); static_assert(std::ranges::drop_view{std::views::all(a), 2}.size() == 1); static_assert(std::ranges::drop_view{std::views::all(a), 3}.size() == 0); static_assert(std::ranges::drop_view{std::views::all(a), 4}.size() == 0); }
参阅
(C++20) |
返回等于范围大小的整数 (定制点对象) |
(C++20) |
返回等于范围大小的有符号整数 (定制点对象) |