std::tuple_size<std:ranges::subrange>

 

C++

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功能特性测试宏 (C++20)

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符号索引

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范围库

范围访问
begin cbegin end cend	rbegin crbegin rend crend	size ssize data cdata	empty
范围转换器
to (C++23)
范围原语
range_size_trange_difference_t range_value_t	range_reference_trange_const_reference_trange_rvalue_reference_t (C++23)	iterator_tconst_iterator_tsentinel_t (C++23)
悬垂迭代器处理
dangling	borrowed_iterator_t	borrowed_subrange_t
范围概念
range borrowed_range    sized_range constant_range (C++23)	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
视图
view_interface	subrange
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empty_viewviews::empty single_viewviews::single	iota_viewviews::iota repeat_viewviews::repeat (C++23)(C++23)	basic_istream_viewviews::istream cartesian_product_viewviews::cartesian_product_view (C++23)(C++23)
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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	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)
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范围适配器闭包对象
range_adaptor_closure (C++23)
辅助项
copyable-box	simple-view

 

std::ranges::subrange

成员函数

subrange::subrange (C++20)

subrange::operator PairLike (C++20)

观察器

subrange::begin (C++20)

subrange::end (C++20)

subrange::empty (C++20)

subrange::size (C++20)

迭代器操作

subrange::advance (C++20)

subrange::next (C++20)

subrange::prev (C++20)

推导指引

非成员函数

get (C++20)

辅助类型

subrange_kind (C++20)

tuple_size (C++20)

tuple_element (C++20)

 

在标头 <ranges> 定义
template< class I, class S, ranges::subrange_kind K > struct tuple_size<ranges::subrange<I, S, K>>     : std::integral_constant<std::size_t, 2> {};		(C++20 起)

std::tuple_size 对 std::ranges::subrange 的部分特化提供编译时获得 subrange 的组分数量的方式，该数始终为 2 。它是为结构化绑定支持提供的。

继承自 std::integral_constant

成员常量

value [静态]

常量值 2 (公开静态成员常量)

成员函数

operator std::size_t	将对象转换到 std::size_t，返回 value (公开成员函数)
operator() (C++14)	返回 value (公开成员函数)

成员类型

类型	定义
value_type	std::size_t
type	std::integral_constant<std::size_t, value>

示例

运行此代码

#include <array>
#include <iostream>
#include <iterator>
#include <ranges>
 
int main()
{
    static_assert(2 == std::tuple_size_v<std::ranges::subrange<int*, int*>>);
 
    using array5 = std::array<int, 5>;
 
    static_assert(2 == std::tuple_size<std::ranges::subrange<
        array5::const_iterator, array5::const_iterator>>{});
 
    constexpr array5 a{ 1, 2, 3, 4, 5 };
 
    std::ranges::subrange sub_a1{a};
 
    for (std::cout << "sub_a1: { "; int e : sub_a1) { std::cout << e << ' '; }
    std::cout << "}\n";
 
    std::ranges::subrange sub_a2{std::next(cbegin(a)), std::prev(cend(a))};
 
    const auto [first, last] = sub_a2;
    std::cout << "sub_a2 size = " << std::distance(first, last) << '\n';
 
    for (std::cout << "sub_a2: { "; int e : sub_a2) { std::cout << e << ' '; }
    std::cout << "}\n";
}

输出：

sub_a1: { 1 2 3 4 5 }
sub_a2 size = 3
sub_a2: { 2 3 4 }

参阅

结构化绑定 (C++17)	绑定指定的名字到初始化器的子对象或元组元素
tuple_size (C++11)	获得元组式类型的元素数 (类模板)
std::tuple_element<std::ranges::subrange> (C++20)	获得 std::ranges::subrange 的迭代器或哨位的类型 (类模板特化)