std::counted_iterator<I>::operator[]

 

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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)
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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)
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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)
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indirect_result_t	projected
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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
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istream_iterator ostream_iterator	istreambuf_iterator ostreambuf_iterator
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advance distance prev (C++11) next (C++11)	ranges::advance (C++20) ranges::distance (C++20) ranges::prev (C++20) ranges::next (C++20)
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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 decltype(auto) operator[]( std::iter_difference_t<I> n ) const     requires std::random_access_iterator<I>;		(C++20 起)

访问位于给定位置的元素。若 n 不小于记录的到末尾的距离则行为未定义。

参数

n

-

相对当前位置的位移

返回值

this->base()[n] 。

示例

运行此代码

#include <iostream>
#include <iterator>
#include <array>
#include <list>
 
int main()
{
    std::array array{'A', 'B', 'C', 'D', 'E'};
 
    std::counted_iterator it{ array.begin() + 1, /*count:*/ 3 };
 
    for (int i{}; i != it.count(); ++i)
        std::cout << it[i] << ' ';
    std::cout << '\n';
 
    for (int i{}; i != it.count(); ++i)
        it[i] += ('E' - 'A');
 
    for (int i{}; i != it.count(); ++i)
        std::cout << it[i] << ' ';
    std::cout << '\n';
 
    std::list list {'X', 'Y', 'Z', 'W'};
    std::counted_iterator it2{ list.begin(), 3 };
//  char x = it2[0]; // 错误：不满足要求 `random_access_iterator`
    std::cout << *it2 << '\n'; // OK
}

输出：

B C D
F G H
X

参阅

operator*operator-> (C++20)

访问被指向的元素 (公开成员函数)