text: #include <vector>
  
  class A
  {
    std::vector<A> _list;
  };
  
  double
  f(const std::vector<double> & input)
  {
    double rv = 0;
    for (auto & element : input)
      rv += element;
    return rv;
  }
  
  int
  main()
  {
    A a;
    std::vector<double> input{1, 2, 3, 4, 5};
    auto rv = f(input);
  }
  