#include <cassert>
#include <exception>
#include <future>
#include <iostream>
#include <stdexcept>
#include <thread>

int main() {
    auto answer = std::async(std::launch::async, [] { return 6 * 7; });
    bool ran = false;
    auto deferred = std::async(std::launch::deferred, [&] {
        ran = true;
        return 7;
    });
    assert(!ran);
    const int delayed = deferred.get();
    assert(ran && delayed == 7);
    assert(!deferred.valid());
    const int value = answer.get();
    assert(value == 42);

    std::promise<int> promise;
    auto failure = promise.get_future();
    std::thread worker([&] {
        try {
            throw std::invalid_argument("negative input");
        } catch (...) {
            promise.set_exception(std::current_exception());
        }
    });
    worker.join();
    bool caught = false;
    try {
        (void)failure.get();
    } catch (const std::invalid_argument&) {
        caught = true;
    }
    assert(caught);
    std::cout << value << ' ' << delayed << ' ' << caught << '\n';
}