std::ranges::split_view<V,Pattern>::begin

 

C++

编译器支持

独立和宿主

语言

标准库

标准库头文件

具名要求

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 (until C++23)  (C++23)	simple-view non-propagating-cache

 

std::ranges::split_view

成员函数

split_view::split_view

split_view::base

split_view::begin

split_view::end

split_view::find_next

嵌套类

split_view::iterator

split_view::sentinel

推导指引

 

constexpr /*iterator*/ begin();		(自 C++20 起)

返回指向首个找到的子范围的迭代器。

为了提供 range 概念要求的均摊常数时间复杂度，此函数将结果缓存在 split_view 内部 (通过 cached_begin_ 成员)，以便在后续调用中使用。

设 base_ 为底层的成员。等价于

constexpr /*iterator*/ begin()
{
    if (!cached_begin_.has_value())
        cached_begin_ = this->find_next(ranges::begin(base_));
    return {*this, ranges::begin(base_), cached_begin_.value()};
}

返回值

迭代器。

复杂度

均摊 \(\scriptsize \mathcal{O}(1)\)O(1)。

示例

运行此代码

#include <iomanip>
#include <iostream>
#include <ranges>
#include <string_view>
 
int main()
{
    constexpr std::string_view sentence{"Keep..moving..forward.."};
    constexpr std::string_view delim{".."};
    std::ranges::split_view words{sentence, delim};
 
    std::cout << "begin(): " << std::quoted(std::string_view{*words.begin()})
              << "\nSubstrings: ";
    for (auto word : words)
        std::cout << std::quoted(std::string_view(word)) << ' ';
 
    std::ranges::split_view letters{sentence, std::string_view{""}};
    std::cout << "\nbegin(): " << std::quoted(std::string_view{*letters.begin()})
              << "\nLetters: ";
    for (auto letter : letters)
        std::cout << std::string_view(letter) << ' ';
    std::cout << '\n';
}

输出

begin(): "Keep"
Substrings: "Keep" "moving" "forward" ""
begin(): "K"
Letters: K e e p . . m o v i n g . . f o r w a r d . .

参见

end	返回指向末尾的迭代器或哨位 (公开成员函数)
begin	返回指向开头的迭代器 (std::ranges::lazy_split_view<V,Pattern> 的公开成员函数)
ranges::begin (C++20)	返回指向范围开头的迭代器 (定制点对象)