//定义分数类，可以用初值构造分数，保证其对象的分母不为0
//重载加法运算符，即实现A+B运算(A、B是分数)
 
#include<iostream>
using namespace std;

class fenshu
{
public:
       fenshu(int m,int z);
       ~fenshu(){};
       friend fenshu operator+(fenshu &f1,fenshu &f2);
       friend ostream & operator<<(ostream &out,fenshu &o);
private:
        int fenzi;
        int fenmu;
};
//实现
fenshu::fenshu(int m,int z)
{               
   fenmu=m;
   fenzi=z;
   if(fenmu==0)
   {
       cout<<"分母不能为零！";
   }
   else
   {   
        cout<<"请重新输入一个分数：";               
        fenmu=m;
        fenzi=z;
}

fenshu operator+(fenshu &f1,fenshu &f2)
{
       return fenshu(f1.fenmu*f2.fenmu,f1.fenzi*f2.fenmu+f2.fenzi*f1.fenmu); //此处提示有错
}

ostream & operator<<(ostream &out,fenshu &o)
{
        out<<o.fenzi<<"/"<<o.fenmu<<endl;
        return out;
}

//主函数               
int main()
{   
    fenshu f1,f2,f3;
    cout<<"请输入分数f1的 分母（空格）分子："<<endl;
    cin>>f1;
    cout<<"请输入分数f2的 分母（空格）分子："<<endl;
    cin>>f2;     
    f3=f1+f2;
    cout<<"f1+f2="<<c3<<endl;
    return 0;
}