c++ - Base and derived classes in Boost.Python -

i have 2 classes - lets , b. class b child class of , both have function h, such that:

class a{   public:   a(){;;}  // ctor   virtual ~a(){ ;; } // destr.   virtual double h(int i,int j){      std::cout<<"calling base function h. level abstract\n";     exit(0);     return 0.0;   }// h };// class 

the derived class b is:

class b : public a{   public:   b(){;;}  // ctor   ~b(){ ;; } // destr.   double h(int i,int j){      return 1.0;   }// h };// class b 

i have function takes arguments of class type:

double f(a x){   return x.h(1,1);  } 

i want use object of derived type b argument function in python. so, export 2 classes , function explained here:

boost_python_module(modab){   class_<a>("a", no_init);    class_<b, bases<a> >("b", init<>())     .def("h", &b::h)   ;        def("f", &f); } 

so in python do:

>>> modab import * >>> x = b() >>> res = f(x) 

as output see method h called base class, not derived class expected:

calling base function h. level abstract 

so, question i'm wrong , possibly miss?

double f(a x) passes x value passing object of type b slice off derived virtual functions.

to fix need pass const a&:

double f(const a& x)