Using a boost coroutine for lazily generating an endless sequence of numbers.

coroutine.cpp

#include <algorithm>
#include <iostream>
#include <vector>

#include <boost/asio/coroutine.hpp>
#include <boost/asio/yield.hpp>

using namespace std;
using namespace boost::asio;

struct endless : coroutine {
    int i = 0;

    int operator()() {
        reenter(this) while (true) {
            yield return i++;
        }
    }
};

int main() {
    endless e;

    for (int i = 0; i < 5; ++i) {
        cout << e() << "\n";
    }
}