future/example6.cpp

// promise::set_exception
#include <iostream>       // std::cin, std::cout, std::ios
#include <functional>     // std::ref
#include <thread>         // std::thread
#include <future>         // std::promise, std::future
#include <exception>      // std::exception, std::current_exception

void get_int (std::promise<int>& prom) {
 int x;
 std::cout << "Please, enter an integer value: ";
 std::cin.exceptions (std::ios::failbit);   // throw on failbit
 try {
   std::cin >> x;                           // sets failbit if input is not int
   prom.set_value(x);
 }
 catch (std::exception&) {
   prom.set_exception(std::current_exception());
 }
}

void print_int (std::future<int>& fut) {
 try {
   int x = fut.get();
   std::cout << "value: " << x << '\n';
 }
 catch (std::exception& e) {
   std::cout << "[exception caught: " << e.what() << "]\n";
 }
}

int main ()
{
 std::promise<int> prom;
 std::future<int> fut = prom.get_future();

 std::thread th1 (print_int, std::ref(fut));
 std::thread th2 (get_int, std::ref(prom));

 th1.join();
 th2.join();
 return 0;
}