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

 

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input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20)	iter_value_titer_difference_titer_reference_titer_const_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++23)(C++20)(C++20)	iterator (C++17 中已弃用) iterator_traits incrementable_traits (C++20) indirectly_readable_traits (C++20)
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std::counted_iterator

成员函数

counted_iterator::counted_iterator

counted_iterator::operator=

counted_iterator::base

counted_iterator::count

counted_iterator::operator*counted_iterator::operator->

counted_iterator::operator[]

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-=

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<std::counted_iterator> (C++20)

 

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

递增或递减底层迭代器 current 和到末尾的距离 length。

如果 length 被设置为负值，这些函数的行为是未定义的。

1) 前递增一次。等效于 ++current; --length; return *this;.

2) 后递增一次。等效于 --length; try { return current++; } catch(...) { ++length; throw; }.

3) 后递增一次。等效于 counted_iterator temp{*this}; ++*this; return temp;.

4) 前递减一次。等效于 --current; ++length; return *this;.

5) 后递减一次。等效于 counted_iterator temp{*this}; --*this; return temp;.

6) 返回一个向前移动了 n 的迭代器适配器。等效于 return counted_iterator(current + n, length - n);.

7) 将迭代器适配器向前移动 n。等效于 current += n; length -= n; return *this;.

8) 返回一个向前移动了 -n 的迭代器适配器。等效于 return counted_iterator(current - n, length + n);.

9) 将迭代器适配器向前移动 -n。等效于 current -= n; length += n; return *this;.

参数

n

-

迭代器适配器递增或递减的步数

返回值

1) *this

2,3) 在更改之前创建的 *this 的副本。

4) *this

5) 在更改之前创建的 *this 的副本。

6) 迭代器适配器，它已前进 n 步。

7) *this

8) 迭代器适配器，它已前进 -n 步。

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)
}

参见

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