C++ member-function function-pointer

mem_func_pointer.cpp

#include <iostream>

class Calculator
{
public:
  int operation(int a, int b) { return (this->*_operation)(a, b); }

  void set_operation(int option)
  {
    switch(option)
    {
      case 0 :
        _operation = &Calculator::add;
        break;
      case 1 :
        _operation = &Calculator::subtract;
        break;
    }
  }

private:
  int add(int a, int b){ return a+b; }

  int subtract(int a, int b){ return a-b; }

private:
  int (Calculator::* _operation)(int, int);

};


int main()
{
  Calculator casio;

  casio.set_operation(0);

  std::cout << "2 + 2 = " << casio.operation(2, 2) << std::endl;

  return 0;
}