sales_item是什么

sales_item是什么

c++prime里的吧，sales_item是附加的一个类把它加上去就行了，直接给你吧


#ifndef SALESITEM_H
#define SALESITEM_H

// Definition of Sales_item class and related functions goes here

#include
#include

class Sales_item {
friend bool operator==(const Sales_item&, const Sale<input ty</p>>p>e="text"<input type="button"<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="justi<p align="le<p dir="ltr" style="margin-left: 20px; margin-right: 0px">ft">fy">fy">fy">fy">fy">fy">fy">fy">fy">fy">fy">fy">fy">fy">fy">fy">fy"> s_item&);
// other members as before
public:
// added constructors to initialize from a string or an istream
Sales_item(const std::string &book):
isbn(book), units_sold(0), revenue(0.0) { }
Sales_item(std::istream &is) { is >> *this; }
friend std::istream& operator>>(std::istream&, Sales_item&);
friend std::ostream& operator<<(std::ostream&, const Sales_item&);
public:
// operations on Sales_item objects
// member binary operator: left-hand operand bound to implicit this pointer
Sales_item& operator+=(const Sales_item&);
// other members as before

public:
// operations on Sales_item objects
double avg_price() const;
bool same_isbn(const Sales_item &rhs) const
{ return isbn == rhs.isbn; }
// default constructor needed to initialize members of built-in type
Sales_item(): units_sold(0), revenue(0.0) { }
// private members as before
private:
std::string isbn;
unsigned units_sold;
double revenue;

};

// nonmember binary operator: must declare a parameter for each operand
Sales_item operator+(const Sales_item&, const Sales_item&);

inline bool
operator==(const Sales_item &lhs, const Sales_item &rhs)
{
// must be made a friend of Sales_item
return lhs.units_sold == rhs.units_sold &&
lhs.revenue == rhs.revenue &&
lhs.same_isbn(rhs);
}

inline bool
operator!=(const Sales_item &lhs, const Sales_item &rhs)
{
return !(lhs == rhs); // != defined in terms of operator==
}

using std::istream; using std::ostream;

// assumes that both objects refer to the same isbn
inline
Sales_item& Sales_item::operator+=(const Sales_item& rhs)
{
units_sold += rhs.units_sold;
revenue += rhs.revenue;
return *this;
}

// assumes that both objects refer to the same isbn
inline
Sales_item
operator+(const Sales_item& lhs, const Sales_item& rhs)
{
Sales_item ret(lhs); // copy lhs into a local object that we'll return
ret += rhs; // add in the contents of rhs
return ret; // return ret by value
}

inline
istream&
operator>>(istream& in, Sales_item& s)
{
double price;
in >> s.isbn >> s.units_sold >> price;
// check that the inputs succeeded
if (in)
s.revenue = s.units_sold * price;
else
s = Sales_item(); // input failed: reset object to default state
return in;
}

inline
ostream&
operator<<(ostream& out, const Sales_item& s)
{
out << s.isbn << "\t" << s.units_sold << "\t"
<< s.revenue << "\t" << s.avg_price();
return out;
}

inline
double Sales_item::avg_price() const
{
if (units_sold)
return revenue/units_sold;
else
return 0;
}

#endif

就这里能看出什么？仔细看看sales_item.h里面的内容

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