text: #include <iostream>
  #include "operation.h"
  using namespace std;
  int main() {
    IFactory *ifa = new AddFactory();
    Operation *oper = ifa->CreateOperation();
    oper->SetValue1(100);
    oper->SetValue2(200);
    cout << "add result:" << oper->GetResult() << endl;
    delete oper;
    delete ifa;
  
    ifa = new SubFactory();
    oper = ifa->CreateOperation();
    oper->SetValue1(100);
    oper->SetValue2(200);
    cout << "sub result:" << oper->GetResult() << endl;
    delete oper;
    delete ifa;
  
    ifa = new MulFactory();
    oper = ifa->CreateOperation();
    oper->SetValue1(100);
    oper->SetValue2(200);
    cout << "mul result:" << oper->GetResult() << endl;
    delete oper;
    delete ifa;
  
    ifa = new DivFactory();
    oper = ifa->CreateOperation();
    oper->SetValue1(100);
    oper->SetValue2(200);
    cout << "div result:" << oper->GetResult() << endl;
    delete oper;
    delete ifa;
    return 0;
  }