packaged_task.cpp

#include <iostream>
#include <thread>
#include <future>
#include <deque>
using namespace std;


std::deque<std::packaged_task<int()>> task_q;
std::mutex mu;
std::condition_variable cond;

int factorial(int N) {
    int res = 1;
    for(int i=N;i>1;i--){
        res *= i;
    }   
    cout <<"The result is : " << res << endl;
    return res;
}

void thread_1(){
    std::packaged_task<int()> t;
    {
        std::unique_lock<std::mutex> locker(mu);
        cond.wait(locker, [](){
            return !task_q.empty();
        });
        t = std::move(task_q.front());
        task_q.pop_front();
    }

    t();
}

int main(){

    std::thread t1(thread_1);
    std::packaged_task<int()> t(std::bind(factorial, 6));
    std::future<int> fu = t.get_future();
    {
        std::lock_guard<std::mutex> locker(mu);
        task_q.push_back(std::move(t));
    }

    cond.notify_one();

    cout << fu.get();
    t1.join();


    return 0;
}