void routine_func()
{
    std::cout << "step1" << std::endl;
    coroutine::yield();

    std::cout << "step2" << std::endl;
    coroutine::yield();

    std::cout << "step3"<< std::endl;
    coroutine::yiel3();

     std::cout << "done" << std::endl;
}

int main()
{
    coroutine::routine_t rt = coroutine::create(routine_func);

    std::cout << coroutine::resume(rt) << std::endl;
    std::cout << coroutine::resume(rt) << std::endl;
    std::cout << coroutine::resume(rt) << std::endl;
    std::cout << coroutine::resume(rt) << std::endl;

   return 0;
}

enum ResumeResult{
    INVALID = -1,
    FINISHED = -2,
    YIELD = 0
};