#include <iostream>
#include <string>
#include <vector>
#include <set>

class Base {
};

template <typename T>
class Derived_CRTP : public Base {
public:

  // a single getter which returns "by name" any object with the name 'data' regardless of its type.
  auto& get_data() { return static_cast<T*>(this)->data; }

};

class Derived1 : public Derived_CRTP<Derived1> {
public:
  // here data is a vector of doubles
  std::vector<double> data = {1,2,3};
};


class Derived2 : public Derived_CRTP<Derived2> {
public:
  // but here its a set of integers
  std::set<int> data = {1};
};



int main() {

  Derived1 d1;
  Derived2 d2;

  // in either case, the get_data function returns the underlying member by name, regardless of its type.
  auto a_vector = d1.get_data();
  auto a_set = d2.get_data();

  // pretty close to duck typing if you ask me!

  return 0;
}