iter_swap (std::common_iterator)

交换两个底层迭代器所指向的对象。如果 x 未持有 I 对象或 y 未持有 I2 对象（即 x 和 y 中至少有一个未持有迭代器），则行为未定义。

函数体等价于 ranges:: iter_swap ( std :: get < I > ( x. var ) , std :: get < I2 > ( y. var ) ) 。

此函数模板对普通的 非限定查找 或 限定查找 不可见，仅当 std::common_iterator<I,S> 作为参数的关联类时，才能通过 实参依赖查找 找到该模板。

#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>
int main()
{
    std::vector<std::string> v1{"1", "2", "3", "4", "5"},
                             v2{"α", "β", "γ", "δ", "ε"};
    using CI = std::common_iterator<
                   std::counted_iterator<std::vector<std::string>::iterator>,
                   std::default_sentinel_t
                   >;
    CI first1{std::counted_iterator{v1.begin(), 3}};
    CI first2{std::counted_iterator{v2.begin(), 4}};
    CI last{std::default_sentinel};
    auto print = [&](auto rem)
    {
        std::cout << rem << "v1 = ";
        std::ranges::copy(v1, std::ostream_iterator<std::string>{std::cout, " "});
        std::cout << "\nv2 = ";
        std::ranges::copy(v2, std::ostream_iterator<std::string>{std::cout, " "});
        std::cout << '\n';
    };
    print("Before iter_swap:\n");
    for (; first1 != last && first2 != last; ++first1, ++first2)
        iter_swap(first1, first2); // ADL
    print("After iter_swap:\n");
}

Before iter_swap:
v1 = 1 2 3 4 5 
v2 = α β γ δ ε 
After iter_swap:
v1 = α β γ 4 5 
v2 = 1 2 3 δ ε