#include <cassert>
#include <condition_variable>
#include <iostream>
#include <mutex>
#include <stop_token>
#include <thread>

int main() {
    int sum = 0;
    {
        std::jthread worker([&] {
            for (int i = 1; i <= 100; ++i) sum += i;
        });
    }
    assert(sum == 5050);

    std::mutex mutex;
    std::condition_variable_any changed;
    bool cancelled = false;
    std::jthread waiter([&](std::stop_token token) {
        std::unique_lock<std::mutex> lock(mutex);
        const bool ready = changed.wait(lock, token, [] { return false; });
        cancelled = !ready && token.stop_requested();
    });
    waiter.request_stop();
    waiter.join();
    assert(cancelled);
    assert(!waiter.joinable());
    std::cout << sum << ' ' << cancelled << '\n';
}