};

class Bulk_item : public Item_base
{
private:
 size_t min_qty;
 double discount;
public:
 //构造函数
 Bulk_item(const string& book = "",double sales_price = 0.0,size_t qty = 0,double disc_rate = 0.0)
  :Item_base(book,sales_price),min_qty(qty),discount(disc_rate)
 {
  cout<<"派生类构造函数"<<endl;
 }

 double net_price(size_t n) const
 {
  if (n >= min_qty)
  {
   return n * (1-discount)*price;
  }
  else
  {
   return n * price;
  }
 }

 //复制构造函数
 Bulk_item(const Bulk_item& b):Item_base(b),min_qty(b.min_qty),discount(b.discount)
 {
  cout<<"派生类复制构造函数"<<endl;
 }
 //赋值重载操作符
 Bulk_item& operator = (const Bulk_item& rhs)
 {
  if (this != &rhs)
  {
   Item_base::operator=(rhs);
  }
  min_qty = rhs.min_qty;
  discount = rhs.discount;
  cout<<"派生类赋值操作符重载"<<endl;
  return *this;
 }
 //虚析构函数
 virtual ~Bulk_item()
 {
  cout<<"派生类析构函数"<<endl;
 }

};
void fun1(Item_base obj)//形参为Item_base
{

}
void fun2(Item_base& obj)//形参为Item_base对象的引用
{

}
Item_base fun3()
{
 Item_base obj;
 return obj;
}

void main()
{
 //调用Item_base的普通构造函数，创建Item_base对象iobj
 Item_base iobj;
 cout<<endl;cout<<endl;

 fun1(iobj);
 cout<<endl;cout<<endl;

 fun2(iobj);
 cout<<endl;cout<<endl;

 iobj=fun3();
 cout<<endl;cout<<endl;

 Item_base *p = new Item_base;
 cout<<endl;cout<<endl;

 delete p;
 cout<<endl;cout<<endl;

 Bulk_item bobj;
 cout<<endl;cout<<endl;

 fun1(bobj);
 cout<<endl;cout<<endl;

 fun2(bobj);
 cout<<endl;cout<<endl;

 Bulk_item *q = new Bulk_item;
 cout<<endl;cout<<endl;

 delete q;

}