C++Primer练习1.6答案

#include <iostream>
#include "Sales_item.h"
using namespace std;

int main(){
    Sales_item item1,item2;
    cin>>item1>>item2;
    if(item1.isbn()==item2.isbn()){
        cout<<item1+item2<<endl;
        return 0;
    }else{
        cerr<<"Data must refer to same ISBN"<<endl;
        return -1;
    }
}