std::ranges::adjacent_view<V,N>::size

 

C++

编译器支持

自立实现与有宿主实现

语言

标准库

标准库标头

具名要求

功能特性测试宏 (C++20)

语言支持库

概念库 (C++20)

诊断库

内存管理库

元编程库 (C++11)

通用工具库

容器库

迭代器库

范围库 (C++20)

算法库

字符串库

文本处理库

数值库

日期和时间库

输入/输出库

文件系统库 (C++17)

并发支持库 (C++11)

执行控制库 (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 reserve_hint (C++26)   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    common_range	sized_range viewable_range    view	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	approximately_sized_range (C++26) 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 as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while common_viewviews::common views::counted to_input_viewviews::to_input (C++26)(C++26)	ref_view drop_viewviews::drop drop_while_viewviews::drop_while lazy_split_viewviews::lazy_split split_viewviews::split join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   concat_viewviews::concat (C++26)(C++26) cache_latest_viewviews::cache_latest (C++26)(C++26)	owning_view 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 (C++23 前)  (C++23)	simple-view non-propagating-cache

 

std::ranges::adjacent_view

成员函数

adjacent_view::adjacent_view

adjacent_view::begin

adjacent_view::end

adjacent_view::size

adjacent_view::reserve_hint (C++26)

迭代器

成员函数

adjacent_view::iterator::iterator

adjacent_view::iterator::operator*

adjacent_view::iterator::operator[]

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

非成员函数

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

operator+(adjacent_view::iterator) operator-(adjacent_view::iterator)

iter_move(adjacent_view::iterator)

iter_swap(adjacent_view::iterator)

哨位

成员函数

adjacent_view::sentinel::sentinel

非成员函数

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

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

 

constexpr auto size() requires ranges::sized_range<V>;		(C++23 起)
constexpr auto size() const requires ranges::sized_range<const V>;		(C++23 起)

返回元素的数量。

令 base_ 为底层视图。等价于：

using SizeType = decltype(ranges::size(base_));
using CommonType = ranges::common_type_t<SizeType, std::size_t>;
auto size = static_cast<CommonType>(ranges::size(base_));
size -= std::min<CommonType>(size, N - 1);
return static_cast<SizeType>(size);

参数

（无）

返回值

元素的数量，当 ranges::size(base_) 小于 N 值时可能为 0。

示例

运行此代码

#include <ranges>

int main()
{
    constexpr static auto v = {1, 2, 3, 4, 5, 6};

    constexpr int width1 {4};
    constexpr auto view1 {std::views::adjacent<width1>(v)};
    static_assert(view1.size() == 3);
    static_assert(view1.size() == (v.size() - width1 + 1));

    constexpr int width2 {8};
    constexpr auto view2 {std::views::adjacent<width2>(v)};
    // 窗口过宽，所以 view2 无元素：
    static_assert(view2.size() == 0);
}

参阅

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