std::iterator_traits<std::common_iterator>

 

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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迭代器库

迭代器概念
indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) input_or_output_iterator (C++20) sentinel_for (C++20) sized_sentinel_for (C++20)	input_iterator (C++20) output_iterator (C++20) forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
迭代器原语
iterator_traits input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20) iterator (C++17 中弃用)	incrementable_traits (C++20) indirectly_readable_traits (C++20) iter_value_titer_difference_titer_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++20)(C++20)
算法概念与工具
间接可调用概念
indirectly_unary_invocableindirectly_regular_unary_invocable (C++20)(C++20) indirect_unary_predicate (C++20)	indirect_binary_predicate (C++20) indirect_equivalence_relation (C++20) indirect_strict_weak_order (C++20)
常用算法要求
indirectly_movable (C++20) indirectly_movable_storable (C++20) indirectly_copyable (C++20) indirectly_copyable_storable (C++20)	indirectly_swappable (C++20) indirectly_comparable (C++20) permutable (C++20) mergeable (C++20) sortable (C++20)
工具
indirect_result_t	projected
迭代器适配器
reverse_iterator move_iterator (C++11) move_sentinel (C++20) common_iterator (C++20) counted_iterator (C++20) basic_const_iterator (C++23) const_iterator (C++23) const_sentinel (C++23) back_insert_iterator front_insert_iterator insert_iterator	make_reverse_iterator (C++14) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20) make_const_iterator (C++23) make_const_sentinel (C++23) back_inserter front_inserter inserter
流迭代器
istream_iterator ostream_iterator	istreambuf_iterator ostreambuf_iterator
迭代器定制点
ranges::iter_move (C++20)
ranges::iter_swap (C++20)
迭代器操作
advance distance prev (C++11) next (C++11)	ranges::advance (C++20) ranges::distance (C++20) ranges::prev (C++20) ranges::next (C++20)
范围访问
begincbegin (C++11)(C++14) endcend (C++11)(C++14) sizessize (C++17)(C++20)	rbegincrbegin (C++14)(C++14) rendcrend (C++14)(C++14) empty (C++17) data (C++17)

 

std::common_iterator

成员函数

common_iterator::common_iterator (C++20)

common_iterator::operator= (C++20)

common_iterator::operator*common_iterator::operator-> (C++20)(C++20)

common_iterator::operator++common_iterator::operator++(int) (C++20)(C++20)

非成员函数

operator== (C++20)

operator- (C++20)

iter_move (C++20)

iter_swap (C++20)

辅助类

incrementable_traits (C++20)

iterator_traits (C++20)

 

在标头 <iterator> 定义
template< std::input_iterator I, class S > struct iterator_traits<std::common_iterator<I, S>>;		(C++20 起)

提供对于 std::common_iterator 类型的属性的统一接口。

成员类型

成员类型	定义
iterator_concept	std::forward_iterator_tag ，若 I 实现 std::forward_iterator ； 否则为 std::input_iterator_tag
iterator_category	std::forward_iterator_tag ，若 std::iterator_traits<I>​::​iterator_category 合法并指代实现 std::derived_from<std::forward_iterator_tag> 的类型； 否则为 std::input_iterator_tag
value_type	std::iter_value_t<I>
difference_type	std::iter_difference_t<I>
pointer	decltype(c.operator->()) ，若它为良构，其中 c 为 const std::common_iterator<I, S> 类型左值； 否则为 void
reference	std::iter_reference_t<I>

示例

运行此代码

#include <vector>
#include <iterator>
#include <type_traits>
 
int main() {
    std::vector v{1,2,3,4};
    using CV = std::common_iterator<
                    std::counted_iterator<std::vector<int>::iterator>,
                    std::default_sentinel_t>;
    CV i { std::counted_iterator { v.begin(), 3 } };
    using TRCV = std::iterator_traits<decltype(i)>;
    static_assert(std::is_same<TRCV::iterator_concept, std::forward_iterator_tag>());
    static_assert(std::is_same<TRCV::iterator_category, std::forward_iterator_tag>());
    static_assert(std::is_same<TRCV::value_type, int>());
    static_assert(std::is_same<TRCV::difference_type, std::vector<int>::difference_type>());
    static_assert(std::is_same<TRCV::pointer, decltype(i.operator->())>());
    static_assert(std::is_same<TRCV::reference, int&>());
 
    CV s { std::default_sentinel };
    using TRCS = std::iterator_traits<decltype(s)>;
    static_assert(std::is_same<TRCS::iterator_concept, std::forward_iterator_tag>());
    static_assert(std::is_same<TRCS::iterator_category, std::forward_iterator_tag>());
    static_assert(std::is_same<TRCS::value_type, int>());
    static_assert(std::is_same<TRCS::difference_type, std::vector<int>::difference_type>());
    static_assert(std::is_same<TRCS::pointer, decltype(s.operator->())>());
    static_assert(std::is_same<TRCS::reference, int&>());
}

参阅

iterator_traits	为迭代器各项性质提供统一接口 (类模板)
std::incrementable_traits<std::common_iterator> (C++20)	计算 std::common_iterator 类型的关联差类型 (类模板特化)