C++多返回值

#include <vector>
#include <iostream>

using namespace std;

template <typename T, typename ... Others>
struct _mr : _mr<Others...>
{
    T& value;
    typedef _mr<Others...> base_type;
    _mr(T& t, base_type& father)
        : value(t),
        base_type(father.value, static_cast<typename base_type::base_type&>(father))
    {
    }

    template <typename Arg>
        _mr<Arg, T, Others...> operator ,(Arg& arg) {
            return _mr<Arg, T, Others...>(arg, *this);
        }

    template <typename Container>
        void operator=(Container && c) {
            auto it = c.begin();
            std::advance(it, sizeof...(Others));
            set(it);
        }

    template <typename Iterator>
        void set(Iterator& it) {
            value = *it--;
            base_type::set(it);
        }
};

template <typename T>
struct _mr<T>
{
    T& value;
    typedef _mr<T> base_type;
    _mr(T& t) : value(t) {}

    _mr(T& t, base_type&) : value(t) {}

    template <typename Arg>
        _mr<Arg, T> operator ,(Arg& arg) {
            return _mr<Arg, T>(arg, *this);
        }

    template <typename Container>
        void operator=(Container && c) {
            auto it = c.begin();
            set(it);
        }

    template <typename Iterator>
        void set(Iterator& it) {
            value = *it;
        }
};

struct _mr0
{
    template <typename T>
        _mr<T> operator ,(T& t) {
            return _mr<T>(t);
        }
};

static _mr0 MR;

std::vector<int> foo() {
    return {3, 4, 5};
}

int main()
{
    int a = 1, b = 2, c = 3;
    (MR, a, b, c) = foo();
    cout << a << b << c << endl;

    return 0;
}