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

 

C++

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迭代器概念
indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) is-integer-like is-signed-integer-like (C++20)(C++20)	sentinel_for (C++20) sized_sentinel_for (C++20) input_iterator (C++20) output_iterator (C++20) input_or_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
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 中弃用) iterator_traits incrementable_traits (C++20) indirectly_readable_traits (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)
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indirect_result_t (C++20)	projected (C++20)	projected_value_t (C++26)
迭代器适配器
reverse_iterator make_reverse_iterator (C++14) move_iterator (C++11) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20)	front_insert_iterator back_insert_iterator inserter insert_iterator front_inserter back_inserter 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) make_const_iterator (C++23) make_const_sentinel (C++23)
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) rbegincrbegin (C++14)(C++14)   endcend (C++11)(C++14) rendcrend (C++14)(C++14)   sizessize (C++17)(C++20) empty (C++17) data (C++17)

 

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)	(C++20 起)
constexpr 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的行为未定义。

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 的副本。

4) *this

5) 更改前创建的 *this 的副本。

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)