std::ranges::join_view<V>::begin

 

C++

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自由（freestanding）与宿主（hosted）

语言

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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

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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 (Ranges library)

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 (Range conversions) std::from_range_t std::from_range (C++23)(C++23)     to (C++23)

悬空迭代器处理 (Dangling iterator handling) dangling borrowed_iterator_t borrowed_subrange_t

范围原语 (Range primitives)
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 concepts)
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 (Range factories)
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 (Range adaptors)
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 (Range generators) std::generator (C++23)

范围适配器闭包对象 (Range adaptor closure objects) range_adaptor_closure (C++23)

范围适配器对象 (Range adaptor objects)

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

 

std::ranges::join_view

成员函数

join_view::join_view

join_view::base

join_view::begin

join_view::end

推导指引

迭代器 (Iterator)

join_view::iterator::iterator

join_view::iterator::operator* join_view::iterator::operator->

join_view::iterator::operator++ join_view::iterator::operator++(int) join_view::iterator::operator-- join_view::iterator::operator--(int)

join_view::iterator::satisfy

operator==(join_view::iterator)

iter_move(join_view::iterator)

iter_swap(join_view::iterator)

哨兵 (Sentinel)

join_view::sentinel::sentinel

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

 

constexpr auto begin();	(1)	(C++20 起)
constexpr auto begin() const     requires ranges::input_range<const V> &&              std::is_reference_v<ranges::range_reference_t<const V>>;	(2)	(C++20 起)

返回指向 join_view 首元素的迭代器。给定 base_ 是底层视图，

1) 等价于

• return /*iterator*/<true>{*this, ranges::begin(base_)}; 如果满足 /*simple-view*/<V> 且 ranges::range_reference_t<V> 是引用类型。否则，
• return /*iterator*/<false>{*this, ranges::begin(base_)};.

2) 等价于 return /*iterator*/<true>{*this, ranges::begin(base_)};。

参数

(无)

返回值

指向第一个元素的迭代器。

注意

当 ranges::range_reference_t<V> 不是引用类型时，即，解引用 V 的迭代器返回一个纯右值临时量，join_view 仅是一个 input_range，在这种情况下只支持单次迭代，并且重复调用 begin() 可能不会给出有意义的结果。

参阅

end	返回一个迭代器或一个哨兵到末尾 (public member function)
ranges::begin (C++20)	返回指向范围开头的迭代器 (customization point object)