std::stack<T,Container>:: swap

#include <iostream>
#include <concepts>
#include <stack>
#include <string>
#include <string_view>
#include <vector>
template<typename Adaptor>
requires (std::ranges::input_range<typename Adaptor::container_type>)
void print(std::string_view name, const Adaptor& adaptor)
{
    struct Printer : Adaptor // 用于访问受保护的 Adaptor::Container c;
    {
        void print(std::string_view name) const
        {
            std::cout << name << " [" << std::size(this->c) << "]: ";
            for (auto const& elem : this->c)
                std::cout << elem << ' ';
            std::cout << '\n';
        }
    };
    static_cast<Printer const&>(adaptor).print(name);
}
int main()
{
    std::vector<std::string> v1{"1","2","3","4"},
                             v2{"Ɐ","B","Ɔ","D","Ǝ"};
    std::stack s1(std::move(v1));
    std::stack s2(std::move(v2));
    print("s1", s1);
    print("s2", s2);
    s1.swap(s2);
    print("s1", s1);
    print("s2", s2);
}