03_async.cpp

#include <future>
#include <iostream>
#include <string>

void printing() {
  std::cout << "printing runs on-" << std::this_thread::get_id() << std::endl;
}

int addition(int x, int y) {
  std::cout << "addition runs on-" << std::this_thread::get_id() << std::endl;
  return x + y;
}

int substract(int x, int y) {
  std::cout << "substract runs on-" << std::this_thread::get_id() << std::endl;
  return x - y;
}

int main() {
  std::cout << "main thread id -" << std::this_thread::get_id() << std::endl;

  int x = 100;
  int y = 50;

  // Runs on different thread
  std::future<void> f1 = std::async(std::launch::async, printing);

  // Runs deferred on the same thread
  std::future<int> f2 = std::async(std::launch::deferred, addition, x, y);

  // Compiler decides.
  std::future<int> f3 =
      std::async(std::launch::deferred | std::launch::async, substract, x, y);

  f1.get();
  std::cout << "value recieved using f2 future -" << f2.get() << std::endl;
  std::cout << "value recieved using f2 future -" << f3.get() << std::endl;
}