std::counted_iterator<I>::operator++,+,+=,--,-,-=

 

C++

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标准库头文件

自立与有宿主实现

具名要求

语言支持库

概念库 (C++20)

诊断库

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容器库

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范围库 (C++20)

算法库

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本地化库

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文件系统库 (C++17)

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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)

 

constexpr counted_iterator& operator++();	(1)	(C++20 起)
decltype(auto) operator++( int );	(2)	(C++20 起)
constexpr counted_iterator operator++( int )   requires std::forward_iterator<I>;	(3)	(C++20 起)
constexpr counted_iterator& operator--()   requires std::bidirectional_iterator<I>;	(4)	(C++20 起)
constexpr counted_iterator operator--( int )   requires std::bidirectional_iterator<I>;	(5)	(C++20 起)
constexpr counted_iterator operator+( std::iter_difference_t<I> n ) const   requires std::random_access_iterator<I>;	(6)	(C++20 起)
constexpr counted_iterator& operator+=( std::iter_difference_t<I> n )   requires std::random_access_iterator<I>;	(7)	(C++20 起)
constexpr counted_iterator operator-( std::iter_difference_t<I> n ) const   requires std::random_access_iterator<I>;	(8)	(C++20 起)
constexpr counted_iterator& operator-=( std::iter_difference_t<I> n )   requires std::random_access_iterator<I>;	(9)	(C++20 起)

增或减底层迭代器 current 和到末尾的距离 length 。

若 length 会被设为负值则这些函数导致未定义行为。

1) 前自增一。等价于 ++current; --length; return *this; 。

2) 后自增一。等价于 --length; try { return current++; } catch(...) { ++length; throw; } 。

3) 后自增一。等价于 counted_iterator temp{*this}; ++*this; return temp; 。

4) 前自减一。等价于 --current; ++length; return *this; 。

5) 后自减一。等价于 counted_iterator temp{*this}; --*this; return temp; 。

6) 返回前进 n 的迭代器。等价于 return counted_iterator(current + n, length - n); 。

7) 令迭代器前进 n 。等价于 current += n; length -= n; return *this; 。

8) 返回前进 -n 的迭代器。等价于 return counted_iterator(current - n, length + n); 。

9) 令迭代器前进 -n 。等价于 current -= n; length += n; return *this; 。

参数

n

-

要增或减迭代器适配器的位置数

返回值

1) *this 。

2-3) 更改前创建的 *this 副本。

4) *this 。

5) 更改前创建的 *this 副本。

6) 前进 n 的迭代器适配器。

7) *this 。

8) 前进 -n 的迭代器适配器。

9) *this 。

示例

运行此代码

#include <cassert>
#include <initializer_list>
#include <iterator>
 
int main()
{
    const auto v = {1, 2, 3, 4, 5, 6};
    std::counted_iterator<std::initializer_list<int>::iterator> it1 {v.begin(), 5};
 
    ++it1;              assert(*it1 == 2 && it1.count() == 4);  // (1)
    auto it2 = it1++;   assert(*it2 == 2 && *it1 == 3);         // (3)
    --it1;              assert(*it1 == 2 && it1.count() == 4);  // (4)
    auto it3 = it1--;   assert(*it3 == 2 && *it1 == 1);         // (5)
    auto it4 = it1 + 3; assert(*it4 == 4 && it4.count() == 2);  // (6)
    auto it5 = it4 - 3; assert(*it5 == 1 && it5.count() == 5);  // (8)
    it1 += 3;           assert(*it1 == 4 && it1.count() == 2);  // (7)
    it1 -= 3;           assert(*it1 == 1 && it1.count() == 5);  // (9)
}

参阅

operator+ (C++20)	令迭代器前进 (函数模板)
operator- (C++20)	计算两个迭代器适配器间的距离 (函数模板)