template<typename Ret, typename...Args>
struct OpenFrame{

    explicit OpenFrame(const std::function<Ret(Args...)>& f):m_f(f)
    {    }

    Ret start(Args...args){
        return m_f(args...);
    }

    std::function<Ret(Args...)> m_f;
};

double print(int i, double d){
    cout<<"print(int i, double d): "<<i<<","<<d<<endl;
    return i+d;
}

int main(){

    std::function func=print;
    OpenFrame frame{func};
    cout<<frame.start(100,3.14)<<endl;
}