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std::move_iterator<Iter>:: operator[]

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Iterator library
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Algorithm concepts and utilities
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(C++20)
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(C++17) (C++20)
(C++17)
(C++17)
/* 未指定 */ operator [ ] ( difference_type n ) const ;
(自 C++17 起为 constexpr)
(C++20 前)
constexpr reference operator [ ] ( difference_type n ) const ;
(自 C++20 起)

返回指定相对位置处元素的引用。

目录

参数

n - 相对于当前位置的偏移量

返回值

std :: move ( current  [ n ] ) (C++20 前) ranges:: iter_move ( current + n ) (C++20 起)

注释

返回类型未指定,因为底层迭代器的 operator [ ] 返回类型同样未指定(参见 LegacyRandomAccessIterator )。

(C++20 前)

示例

#include <cstddef>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <string>
#include <vector>
void print(auto rem, const auto& v)
{
    for (std::cout << rem; const auto& e : v)
        std::cout << std::quoted(e) << ' ';
    std::cout << '\n';
}
int main()
{
    std::vector<std::string> p{"alpha", "beta", "gamma", "delta"}, q;
    print("1) p: ", p);
    std::move_iterator it{p.begin()};
    for (std::size_t t{}; t != p.size(); ++t)
        q.emplace_back(it[t]); 
    print("2) p: ", p);
    print("3) q: ", q);
    std::list l{1, 2, 3};
    std::move_iterator it2{l.begin()};
//  it2[1] = 13; // 编译错误:底层迭代器
                 // 不满足随机访问迭代器要求
//  *it2 = 999;  // 编译错误:将右值用作左值
}

可能的输出:

1) p: "alpha" "beta" "gamma" "delta"
2) p: "" "" "" ""
3) q: "alpha" "beta" "gamma" "delta"

参见

访问所指向的元素
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