std::ranges::zip_view<Views...>::size

 

C++

编译器支持

独立和托管

语言

标准库

标准库头文件

命名要求

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

迭代器库

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

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

 

std::ranges::zip_view

成员函数

zip_view::zip_view

zip_view::begin

zip_view::end

zip_view::size

推导指南

迭代器

成员函数

zip_view::iterator::iterator

zip_view::iterator::operator*

zip_view::iterator::operator[]

zip_view::iterator::operator++ zip_view::iterator::operator++(int) zip_view::iterator::operator-- zip_view::iterator::operator--(int) zip_view::iterator::operator+= zip_view::iterator::operator-=

非成员函数

operator==(zip_view::iterator) operator<(zip_view::iterator) operator>(zip_view::iterator) operator<=(zip_view::iterator) operator>=(zip_view::iterator) operator<=>(zip_view::iterator)

operator+(zip_view::iterator) operator-(zip_view::iterator)

iter_move(zip_view::iterator)

iter_swap(zip_view::iterator)

哨兵

成员函数

zip_view::sentinel::sentinel

非成员函数

operator==(zip_view::iterator,zip_view::sentinel)

operator-(zip_view::iterator,zip_view::sentinel)

 

constexpr auto size()     requires (ranges::sized_range<Views> && ...);	(1)	(自 C++23 起)
constexpr auto size() const     requires (ranges::sized_range<const Views> && ...);	(2)	(自 C++23 起)

返回 zip_view 中的元素数量。仅当每个底层（自适应）范围满足 sized_range 时才提供。

等效于

return std::apply
(
    [](auto... sizes)
    {
        using CT = /*make-unsigned-like-t*/<std::common_type_t<decltype(sizes)...>>;
        return ranges::min({CT(sizes)...});
    },
    /*tuple-transform*/(ranges::size, views_)
);

参数

(无)

返回值

元素数量，它是所有自适应 view 大小中的最小值。

示例

运行此代码

#include <algorithm>
#include <cassert>
#include <deque>
#include <forward_list>
#include <ranges>
#include <vector>
 
int main()
{
    auto x = std::vector{1, 2, 3, 4, 5};
    auto y = std::deque{'a', 'b', 'c'};
    auto z = std::forward_list{1., 2.};
 
    auto v1 = std::views::zip(x, y);
    assert(v1.size() == std::min(x.size(), y.size()));
    assert(v1.size() == 3);
 
    [[maybe_unused]] auto v2 = std::views::zip(x, z);
//  auto sz = v2.size(); // Error, v2 does not have size():
    static_assert(not std::ranges::sized_range<decltype(z)>);
}

参见

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