std::ranges::common_view<V>::size

 

C++

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独立和托管

语言

标准库

标准库头文件

命名需求

功能测试宏 (C++20)

语言支持库

概念库 (C++20)

元编程库 (C++11)

诊断库

通用实用程序库

字符串库

容器库

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范围库 (C++20)

算法库

数值库

本地化库

输入/输出库

文件系统库 (C++17)

正则表达式库 (C++11)

并发支持库 (C++11)

执行支持库 (C++26)

技术规范

符号索引

外部库

 

范围库

范围访问 begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata empty

范围转换 std::from_range_t std::from_range (C++23)(C++23)     to (C++23)

悬垂迭代器处理 dangling borrowed_iterator_t borrowed_subrange_t

范围原语
range_size_trange_difference_trange_value_t elements_of (C++23)	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_reference_trange_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)

范围概念
range borrowed_range    sized_range	common_range view viewable_range	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	constant_range (C++23)

视图
view_interface	subrange

范围工厂
empty_viewviews::empty	single_viewviews::single	basic_istream_viewviews::istream	iota_viewviews::iota	repeat_viewviews::repeat (C++23)(C++23)

范围适配器
views::all_tviews::all ref_view owning_view as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while concat_viewviews::concat (C++26)(C++26)	drop_viewviews::drop drop_while_viewviews::drop_while join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   lazy_split_viewviews::lazy_split split_viewviews::split views::counted common_viewviews::common	reverse_viewviews::reverse as_const_viewviews::as_const (C++23)(C++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (C++23)(C++23) zip_viewviews::zip (C++23)(C++23) zip_transform_viewviews::zip_transform (C++23)(C++23)	adjacent_viewviews::adjacent (C++23)(C++23) views::pairwise (C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23) views::pairwise_transform (C++23) chunk_viewviews::chunk (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23) stride_viewviews::stride (C++23)(C++23) cartesian_product_viewviews::cartesian_product (C++23)(C++23)

范围生成器 std::generator (C++23)

范围适配器闭包对象 range_adaptor_closure (C++23)

范围适配器对象

辅助项
copyable-box movable-box (直到 C++23)  (C++23)	simple-view non-propagating-cache

 

std::ranges::common_view

成员函数

common_view::common_view

common_view::base

common_view::begin

common_view::end

common_view::size

推断指南

 

constexpr auto size() requires ranges::sized_range<V>;	(1)	(自 C++20)
constexpr auto size() const requires ranges::sized_range<const V>;	(2)	(自 C++20)

返回元素数量。

等同于 return ranges::size(base_);，其中 base_ 是底层视图。

参数

(无)

返回值

元素数量。

示例

运行这段代码

#include <ranges>
#include <string_view>
 
int main()
{
    constexpr static auto v1 = {1, 2, 3, 4, 5};
    constexpr auto common1 { v1 | std::views::common };
    static_assert(common1.size() == 5);
 
    constexpr auto take3 { v1 | std::views::reverse | std::views::take(3) };
    constexpr auto common2 { take3 | std::views::common };
    static_assert(common2.size() == 3);
 
    using namespace std::literals;
    constexpr static auto v2 = { "∧"sv, "∨"sv, "∃"sv, "∀"sv };
    static_assert(std::ranges::views::common(v2).size() == 4);
}

另请参见

ranges::size (C++20)	返回一个等于范围大小的整数 (自定义点对象)
ranges::ssize (C++20)	返回一个等于范围大小的有符号整数 (自定义点对象)