gistfile1.cpp

    struct counter : resource { int c; } r;
    counter r2;

    std::function<bool(int&)> is7 = [](int& x) -> bool { return x == 7; };
    r2.with_do([&]() {
        if( r2.c != 7 )
        {
            std::cout << "Waiting for c to become 7.\n";
        }
        r.await(std::bind(is7, std::ref(r2.c))); // r != r2
        std::cout << "c is 7!\n";
    });