operator+(std::counted_iterator)

 

C++

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技术规范

 

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) 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) 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::counted_iterator

成员函数

counted_iterator::counted_iterator (C++20)

counted_iterator::operator= (C++20)

counted_iterator::base (C++20)

counted_iterator::count (C++20)

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

counted_iterator::operator[] (C++20)

counted_iterator::operator++counted_iterator::operator++(int)counted_iterator::operator+counted_iterator::operator+=counted_iterator::operator--counted_iterator::operator--(int)counted_iterator::operator-counted_iterator::operator-= (C++20)(C++20)(C++20)(C++20)(C++20)(C++20)(C++20)(C++20)

非成员函数

operator==operator<=> (C++20)(C++20)

operator==(default_sentinel_t) (C++20)

operator+ (C++20)

operator- (C++20)

operator-(default_sentinel_t) (C++20)

iter_move (C++20)

iter_swap (C++20)

辅助类

iterator_traits (C++20)

 

friend constexpr counted_iterator operator+(   std::iter_difference_t<I> n, const counted_iterator& x )     requires std::random_access_iterator<I>;		(C++20 起)

返回前进 n 个位置的迭代器适配器。若 n 大于 x 内记录的长度（即若 x + n 导致未定义行为）则行为未定义。

此函数对通常无限定或有限定查找不可见，而只能在 std::counted_iterator<I> 为参数的关联类时由实参依赖查找找到。

参数

n	-	要增加迭代器的位置数
x	-	要增加的迭代器

返回值

等于 x + n 的迭代器适配器。

示例

运行此代码

#include <iostream>
#include <iterator>
#include <list>
#include <vector>
 
int main()
{
    std::vector v { 0, 1, 2, 3, 4, 5 };
    std::counted_iterator<std::vector<int>::iterator> p{ v.begin() + 1, 4 };
    std::cout << "*p:" << *p << ", count:" << p.count() << '\n';
    std::counted_iterator<std::vector<int>::iterator> q{ 2 + p };
    std::cout << "*q:" << *q << ", count:" << q.count() << '\n';
 
    std::list l { 6, 7, 8, 9 };
    std::counted_iterator<std::list<int>::iterator> r{ l.begin(), 3 };
    std::cout << "*r:" << *r << ", count:" << r.count() << '\n';
//  auto s { 2 + r }; // 错误：底层迭代器不实现 std::random_access_iterator
}

输出：

*p:1, count:4
*q:3, count:2
*r:6, count:3

参阅

operator++operator++(int)operator+=operator+operator--operator--(int)operator-=operator- (C++20)	推进或回退迭代器 (公开成员函数)
operator- (C++20)	计算两个迭代器适配器间的距离 (函数模板)
operator-(std::default_sentinel_t) (C++20)	计算到末尾的有符号距离 (函数模板)