【C++ Primer 第7章】定义抽象数据类型

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参考资料

1. C++Primer #7 类

Sales_data类

Sales_data.h

#include<iostream>
#include<string> class Sales_data
{
friend std::istream& operator >> (std::istream&, Sales_data&);
friend std::ostream& operator << (std::ostream&, Sales_data&);
friend Sales_data operator + (const Sales_data&, const Sales_data&);
friend bool operator == (const Sales_data&, const Sales_data&)
public:
Sales_data() = default;
Sales_data(std::string s): bookNo(s), units_sold(), revenue(0.0) {}
Sales_data(std::string s, unsigned n, double p): bookNo(s), units_sold(n), revenue(p) {}
public:
string isbn() const { return bookNo; }
Sales_data& operator += (const Sales_data&);
private:
string bookNo; //书籍编号
double units_sold = ; //销售量
double sellingprice = 0.0; //原始价格
double salesprice = 0.0; //实售价格
double discount = 0.0; //折扣量
};

Sales_data.cpp

#include"Sales_data.h"
#include<iostream>
#include<string> bool Sales_data::operator == (const Sales_data &lhs, const Sales_data &rhs)
{
return lhs.units_sold == rhs.units_sold &&
lhs.sellprice == rhs.sellprice &&
lhs.salesprice == rhs.salesprice &&
lhs.isbn() == rhs.isbn();
} Sales_data Sales_data::operator + (const Sales_data &lhs, const Sales_data &rhs)
{
Sales_data ret(lhs);
ret += rhs;
return ret;
} Sales_data& Sales_data::operator += (const Sales_data &rhs)
{
units_sold += rhs.units_sold;
salesprice = (units_sold * salesprice + rhs.units_sold * rhs.salesprice)
/ (units_sold + rhs.units_sold);
if(sellprice != )
discount = salesprice / sellprice;
return *this;
} istream& Sales_data::operator >> (std::istream &in, Sales_data &s)
{
in >> s.bookNo >> s.sellprice >> s.salesprice;
if(in && s.sellingprice != )
s.discount = s.salesprice / s.sellprice;
else
s = Sales_data();
} ostream& Sales_data::operator << (std::ostream &os, const Sales_data &s)
{
os << s.isbn() << " " << s.units_sold << " " << s.sellprice << " "
<< s.salesprice << " " << s.discount;
return os;
}