class cut:public add{protected: int num3; int num4;public: cut(int nn1, int nn2,int nn3,int nn4, int sum2 = 0,int temp=0):add(nn1,nn2) { num3 = nn3; num4 = nn4; } cut operator-(cut n) { cut temp;//這里說(shuō)不存在默認(rèn)構(gòu)造函數(shù)，特黑體 temp.num3 = num3 + n.num3; temp.num4 = num4 + n.num4; return temp; }