TheArtOfHPC_vol3_cppf08programming/Code/object/polymorph2.cpp

/****************************************************************
 ****
 **** This file belongs with the course
 **** Introduction to Scientific Programming in C++/Fortran2003
 **** copyright 2016-2021 Victor Eijkhout eijkhout@tacc.utexas.edu
 ****
 **** polymorphic2.cxx : example
 ****
 ****************************************************************/

#include <iostream>
using std::cin;
using std::cout;

#include <vector>
using std::vector;

#include <functional>
using std::function;

class lib {
public:
  lib() {};
  function< int() > give{ [] () { return 0; } };
  //  lib( const lib& l ) { give = l.give; };
};
class lib1 : public lib {
public:
  lib1() : lib() { give = [] () { return 1; }; };
};
class lib2 : public lib {
public:
  lib2() : lib() { give = [] () { return 2; }; };
};

int main() {

  // we can invoke the specific library
  lib1 specific;
  cout << specific.give() << '\n';

  // if we use the copy contructor we also get the `derived' funciton
  lib mylib( specific );
  cout << mylib.give() << '\n';

  return 0;
}