What would be a “Hello, World!” example for “std::ref”?

Question

Can somebody give a simple example which demonstrates the functionality of std::ref? I mean an example in which some other constructs (like tuples, or data type tem

Answer 1

// Producer Consumer Problem

#include 
#include 
#include 
#include 
#include 
using namespace std;

class Buffer {

    std::mutex m;
    std::condition_variable cv;
    std::deque queue;
    const unsigned long size = 1000;

    public:
    void addNum(int num) {
        std::unique_lock lock(m);
        cv.wait(lock, [this]() { return queue.size() <= size; });
        queue.push_back(num);
        cout << "Pushed " << num << endl;
        lock.unlock();
        cv.notify_all();
    }
    int removeNum() {
        std::unique_lock lock(m);
        cv.wait(lock, [this]() { return queue.size()>0; });
        int num = queue.back();
        queue.pop_back();
        cout << "Poped " << num << endl;
        lock.unlock();
        cv.notify_all();
        return num;
    }

};

void producer(int val, Buffer& buf) {
    for(int i=0; i

Just another use of std::ref in main while passing Buffer object as reference in producer and consumer. If std::ref not used then this code will not compile.