[#tour-race]
== race

If multiple <<awaitable, awaitables>> work in parallel,
but we want to be notified if either completes, we shall use <<race, race>>.

[source,cpp]
----
cobalt::generator<int> some_data_source();
cobalt::generator<double> another_data_source();

cobalt::main co_main(int argc, char * argv[])
{
    auto g1 = some_data_source();
    auto g2 = another_data_source();

    int res1    = co_await g1;
    double res2 = co_await g2;

    printf("Result: %f", res1 * res2);

    while (g1 && g2)
    {
        switch(variant2::variant<int, double> nx = co_await cobalt::race(g1, g2))
        {
            case 0:
                res1 = variant2::get<0>(nx);
                break;
            case 1:
                res2 = variant2::get<1>(nx);
                break;
        }
        printf("New result: %f", res1 * res2);
    }

    co_return 0;
}
----

NOTE: `race` in this context will not cause any data loss.