#include <iostream>
#include <functional>
#include <memory>
 
struct A {
  virtual void operator()() {
    std::cout << "classA" << std::endl;
  }
  virtual ~A() {}
};
 
struct B : public A {
  void operator()() {
    std::cout << "classB" << std::endl;
  }
};
 
struct C : public B {
  void operator()() final {
    std::cout << "classC" << std::endl;
  }
};
 
int main()
{
  std::function<void(void)>func[] = {
    A(),
    B(),
    C(),
  };
 
  for (auto a : func)
    a();
}

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