/** @file  packaged_task.cpp

*  @note

*  @brief

*  @author

*  @date   2019-8-15

*  @note

*  @history

*  @warning

*/

// packaged_task example

#include <iostream>     // std::cout

#include <future>       // std::packaged_task, std::future

#include <chrono>       // std::chrono::seconds

#include <thread>       // std::thread, std::this_thread::sleep_for

// count down taking a second for each value:

int countdown (int from, int to) {

    for (int i=from; i!=to; --i) {

        std::cout << i << '\n';

        std::this_thread::sleep_for(std::chrono::milliseconds());

    }

    std::cout << "Lift off!\n";

    return from-to;

}

int main ()

{

    std::packaged_task<int(int,int)> tsk (countdown);   // set up packaged_task

    std::future<int> ret = tsk.get_future();            // get future

    std::thread th (std::move(tsk),,);   // spawn thread to count down from 10 to 0

    // ...

    int value = ret.get();                  // wait for the task to finish and get result

    std::cout << "The countdown lasted for " << value << " seconds.\n";

    th.join();

    return ;

}