std::tie

#include <iostream>
#include <string>
#include <set>
#include <tuple>

struct S {
    int n;
    std::string s;
    float d;
    bool operator<(const S& rhs) const
    {
        //  n  rhs.n,
        //  s  rhs.s,
        //  d  rhs.d
        return std::tie(n, s, d) < std::tie(rhs.n, rhs.s, rhs.d);
    }
};

int main()
{
    //   : //

    std::set<S> set_of_s; // S  LessThanComparable

    S value{42, "", 3.14};
    std::set<S>::iterator iter;
    bool inserted;

    //    insert  iter  inserted
    std::tie(iter, inserted) = set_of_s.insert(value);
    assert(inserted);

    // std::tie       C++17: //

    auto position = [](int w) { return std::tuple<int, int>{ 1 * w, 2 * w }; };

    auto [x, y] = position(1);
    assert(x == 1 and y == 2);
    // ...
    std::tie(x, y) = position(2); // reuse x, y with tie
    assert(x == 2 and y == 4);

    // ,   ,  
    auto coordinates = [] { return std::tuple<char, short>(6, 9); };
    // ...
    std::tie(x, y) = coordinates(); //  
    assert(x == 6 and y == 9);
}