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hello-world-concurrency.cpp

// "Copyright [2016] <Asit Dhal, dhal.asitk@gmail.com>"

#include <thread>
#include <iostream>
#include <chrono>
#include <string>
#include <sstream>
#include <functional>
#include <algorithm>
#include <vector>

// returns thread id in std::string
std::string get_str_id() {
    auto myid = std::this_thread::get_id();
    std::stringstream ss;
    ss << "[id=" << myid << "] ";
    return ss.str();
}

class worker {
 public:
    explicit worker(std::string name):name(name) {
        thd = std::thread(&worker::execute, this);
    }

    void execute() const {
        std::cout << get_str_id() << name << std::endl;
        heavy_work();
    }

    void heavy_work() const {
        std::cout << get_str_id() << "in heavy work" << std::endl;
        std::this_thread::sleep_for(std::chrono::seconds(2));
    }

    void join() {
        thd.join();
    }

 private:
    std::thread thd;
    std::string name;
};

void do_work(int id) {
    std::cout << get_str_id() << "in do work, id=" << id << std::endl;
    std::this_thread::sleep_for(std::chrono::seconds(2));
}

int main() {
    std::cout << get_str_id() << "Main thread " << std::endl;

    std::vector<std::thread> threads;
    for (int i=0; i < 3; i++) {
        threads.push_back(std::thread(do_work, i));
    }

    std::for_each(threads.begin(), threads.end(),
        std::mem_fn(&std::thread::join));

    std::vector<worker> workers;
    for (int i=0; i < 3; i++) {
        workers.push_back(worker(std::string("thread:") + std::to_string(i)));
    }

    std::for_each(workers.begin(), workers.end(),
        std::mem_fn(&worker::join));

    std::cout << "main ended" << std::endl;

    return 0;
}

auto result = main();

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// As C++ does not allow to redefine symbols, pressing "play" multiple times might cause errors.
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