// promiseFuture.cpp
#include <future>
#include <iostream>
#include <thread>
#include <utility>
void product(std::promise<int>&& intPromise, int a, int b){
  intPromise.set_value(a*b);
}
struct Div{
  void operator() (std::promise<int>&& intPromise, int a, int b) const {
    intPromise.set_value(a/b);
  }
};
int main(){
  int a= 20;
  int b= 10;
  std::cout << std::endl;
  // define the promises
  std::promise<int> prodPromise;
  std::promise<int> divPromise;
  // get the futures
  std::future<int> prodResult= prodPromise.get_future();
  std::future<int> divResult= divPromise.get_future();
  // calculate the result in a separat thread
  std::thread prodThread(product,std::move(prodPromise),a,b);
  Div div;
  std::thread divThread(div,std::move(divPromise),a,b);
  // get the result
  std::cout << "20*10= " << prodResult.get() << std::endl;
  std::cout << "20/10= " << divResult.get() << std::endl;
  prodThread.join();
  
  divThread.join();
  std::cout << std::endl;
}