std::ranges::drop_view<V>:: size

令 base_ 为底层视图， count_ 为存储的计数（传递给构造函数的数值，若 * this 为默认构造则值为 ​ 0 ​ ）。等效于

const auto s = ranges:: size ( base_ ) ;
const auto c = static_cast < decltype ( s ) > ( count_ ) ;
return s < c ? 0 : s - c ;

返回值

元素数量。

示例

#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 &&
        std::ranges::drop_view{std::views::all(a), 1}.size() == 2 &&
        std::ranges::drop_view{std::views::all(a), 2}.size() == 1 &&
        std::ranges::drop_view{std::views::all(a), 3}.size() == 0 &&
        std::ranges::drop_view{std::views::all(a), 4}.size() == 0
    );
}

参见