Solution: Promise to Deliver

#include <iostream>
#include <thread>
#include <future>
#include <stdexcept>
void asyncDivision(std::promise<double>&& p, double num, double den) {
    if (den == 0.0) {
        // We cannot return an exception, we must store it in the promise
        p.set_exception(std::make_exception_ptr(std::runtime_error("Division by zero error!")));
    } else {
        // Calculation successful, store the value
        p.set_value(num / den);
    }
}
int main() {
    double num = 10.0;
    double den = 0.0; // Change to 2.0 to see success case
    // 1. Create the promise
    std::promise<double> divPromise;
    // 2. Get the future associated with this promise
    std::future<double> divResult = divPromise.get_future();
    // 3. Launch thread, moving the promise into it
    std::thread t(asyncDivision, std::move(divPromise), num, den);
    try {
        std::cout << "Waiting for result...\n";
        // 4. Block and wait. If the thread set an exception, it is thrown here
        double result = divResult.get();
        std::cout << "Result: " << result << "\n";
    } catch (const std::exception& e) {
        // 5. Catch the exception propagated from the background thread
        std::cout << "Caught exception from thread: " << e.what() << "\n";
    }
    t.join(); // Always join manual threads
    return 0;
}