C++ Primer 0x07 练习题解

Posted 2022-02-04 鱼竿钓鱼干

📔 C++ Primer 0x07 练习题解

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7.1 定义抽象数据类型

7.1.1 定义抽象数据类型

7.1 使用2.6.1节定义的Sales_data类为 1.6节 的交易处理程序编写一个新版本。

#include <iostream>
#include <string>

struct Sales_data 
	std::string bookNo;
	unsigned units_sold = 0;
	double revenue = 0.0;
;

int main()
	Sales_data total,item;
    double price = 0;
    if (std::cin >> total.bookNo >> total.units_sold >> price)
        total.revenue = total.units_sold * price;
        while (std::cin >> item.bookNo >> item.units_sold >> price)
            item.revenue = item.units_sold * price;
            if (total.bookNo == item.bookNo) 
                total.units_sold += item.units_sold;
                total.revenue += item.revenue;
            else 
                std::cout << total.bookNo << " " 
                		<< total.units_sold << " "
                		<< total.revenue << std::endl;
                total = item;
            
        
        std::cout << total.bookNo << " " 
				<< total.units_sold << " "
				<< total.revenue << std::endl;
    else 
        std::cerr << "No data?!" << std::endl;
        return -1;
    
	return 0;

7.1.2 定义改进的 Salses_data 类

7.2 曾在2.6.2节的练习中编写了一个Sales_data类，请向这个类添加combine函数和isbn成员。

7.3 修改7.1.1节的交易处理程序，令其使用这些成员。

#include <iostream>
#include <string>

struct Sales_data 
	std::string bookNo;
	unsigned units_sold = 0;
	double revenue = 0.0;
	
	Sales_data& combine(const Sales_data &rhs);
	std::string isbn()return bookNo;
;

Sales_data& Sales_data::combine(const Sales_data &rhs)
	units_sold += rhs.units_sold;
	revenue += rhs.revenue;
	return *this;


int main()
	Sales_data total,item;
	double price = 0;
    if (std::cin >> total.bookNo >> total.units_sold >> price)
    	total.revenue = total.units_sold * price;
        while (std::cin >> item.bookNo >> item.units_sold >> price)
        	item.revenue = item.units_sold * price;
            if (total.isbn() == item.isbn()) 
                total.combine(item);
            else 
                std::cout << total.bookNo << " " 
                		<< total.units_sold << " "
                		<< total.revenue << std::endl;
                total = item;
            
        
        std::cout << total.bookNo << " " 
				<< total.units_sold << " "
				<< total.revenue << std::endl;
    else 
        std::cerr << "No data?!" << std::endl;
        return -1;
    
	return 0;

7.4 编写一个名为Person的类，使其表示人员的姓名和地址。使用string对象存放这些元素，接下来的练习将不断充实这个类的其他特征。

struct Person
	std::string name;
	std::string address;
;

7.5 在你的Person类中提供一些操作使其能够返回姓名和地址。 这些函数是否应该是const的呢？解释原因。

struct Person
	std::string name;
	std::string address;
	std::string get_name()constreturn name;
	std::string get_address()constreturn address;
;

应该加，考虑常量对象可能也要使用这些操作

7.1.3 定义类相关的非成员函数

7.6 对于函数add、read和print，定义你自己的版本。

7.7 使用这些新函数重写7.1.2节练习中的程序。

#include <iostream>
#include <string>


struct Sales_data 
	std::string bookNo;
	unsigned units_sold = 0;
	double revenue = 0.0;
	
	Sales_data& combine(const Sales_data &rhs);
	std::string isbn()constreturn bookNo;
;

Sales_data& Sales_data::combine(const Sales_data &rhs)
	units_sold += rhs.units_sold;
	revenue += rhs.revenue;
	return *this;


std::istream & read(std::istream &is,Sales_data &item)
	double price = 0;
	is >> item.bookNo >> item.units_sold >> price;
	item.revenue = item.units_sold * price;
	return is;


std::ostream & print(std::ostream &os,const Sales_data &item)
	os << item.isbn() << " "<< item.units_sold << " "<< item.revenue;
	return os;


Sales_data add(const Sales_data &lhs,const Sales_data &rhs)
	Sales_data sum = lhs;
	sum.combine(rhs);
	return sum;


int main()
	Sales_data total,item;
    if (read(std::cin,total))
        while (read(std::cin,item))
            if (total.isbn() == item.isbn()) 
                total.combine(item);
            else 
                print(std::cout,total);
                std::cout << std::endl;
                total = item;
            
        
        print(std::cout,total);
        std::cout << std::endl;
        
    else 
        std::cerr << "No data?!" << std::endl;
        return -1;
    
	return 0;

7.8 为什么read函数将其Sales_data参数定义成普通的引用，而print函数将其参数定义成常量引用？

read 会改变Sales_data item的内容，print不会

7.9 对于7.1.2节练习中代码，添加读取和打印Person对象的操作。

#include <iostream>
#include <string>

struct Person
	std::string name;
	std::string address;
	std::string get_name()constreturn name;
	std::string get_address()constreturn address;
;

std::istream& read(std::istream &is,Person &p)
	is >> p.name >> p.address;
	return is;


std::ostream& print(std::ostream &os,const Person &p)
	os << p.get_name() << " " << p.get_address();
	return os;

int main()
	Person p;
	read(std::cin,p);
	print(std::cout,p);
	return 0;

7.10 在下面这条if语句中，条件部分的作用是什么？

if (read(read(cin, data1), data2)) //连续读入 data1 data2 的数据

7.1.4 构造函数

7.11 在你的Sales_data类中添加构造函数， 然后编写一段程序令其用到每个构造函数。

#include <iostream>
#include <string>


struct Sales_data 
	Sales_data() = default;
	Sales_data(const std::string &s):bookNo(s)
	Sales_data(const std::string &s,unsigned u,double p)
		:bookNo(s),units_sold(u),revenue(u*p)
	Sales_data(std::istream &);
	
	std::string bookNo;
	unsigned units_sold = 0;
	double revenue = 0.0;
	
	Sales_data& combine(const Sales_data &rhs);
	std::string isbn()constreturn bookNo;
	double avg_price()const;
;


double Sales_data::avg_price()const
	return units_sold?(revenue/units_sold):0;


Sales_data& Sales_data::combine(const Sales_data &rhs)
	units_sold += rhs.units_sold;
	revenue += rhs.revenue;
	return *this;


std::istream & read(std::istream &is,Sales_data &item)
	double price = 0;
	is >> item.bookNo >> item.units_sold >> price;
	item.revenue = item.units_sold * price;
	return is;


std::ostream & print(std::ostream &os,const Sales_data &item)
	os << item.isbn() << " "<< item.units_sold << " "
		<< item.revenue << " " << item.avg_price();
	return os;


Sales_data::Sales_data(std::istream &is)
	read(is,*this);


Sales_data add(const Sales_data &lhs,const Sales_data &rhs)
	Sales_data sum = lhs;
	sum.combine(rhs);
	return sum;


int main()
	Sales_data A;
	print(std::cout,A) << std::endl;
	
	Sales_data B("bookB");
	print(std::cout,B) << std::endl;
	
	Sales_data C("bookC",12,3.0);
	print(std::cout,C) << std::endl;
	
	Sales_data D(std::cin);
	print(std::cout,D) << std::endl;
	
	return 0;

7.12 把只接受一个istream作为参数的构造函数移到类的内部。

#include <iostream>
#include <string>

struct Sales_data;
std::istream &read(std::istream&,Sales_data&);

struct Sales_data 
	Sales_data() = default;
	Sales_data(const std::string &s):bookNo(s)
	Sales_data(const std::string &s,unsigned u,double p)
		:bookNo(s),units_sold(u),revenue(u*p)
	Sales_data(std::istream &is)read(is,*this);
	
	std::string bookNo;
	unsigned units_sold = 0;
	double revenue = 0.0;
	
	Sales_data& combine(const Sales_data &rhs);
	std::string isbn()constreturn bookNo;
	double avg_price()const;
;


double Sales_data::avg_price()const
	return units_sold?(revenue/units_sold):0;


Sales_data& Sales_data::combine(const Sales_data &rhs)
	units_sold += rhs.units_sold;
	revenue += rhs.revenue;
	return *this;


std::istream & read(std::istream &is,Sales_data &item)
	double price = 0;
	is >> item.bookNo >> item.units_sold >> price;
	item.revenue = item.units_sold * price;
	return is;


std::ostream & print(std::ostream &os,const Sales_data &item)
	os << item.isbn() << " "<< item.units_sold << " "
		<< item.revenue << " " << item.avg_price();
	return os;


Sales_data add(const Sales_data &lhs,const Sales_data &rhs)
	Sales_data sum = lhs;
	sum.combine(rhs);
	return sum;


int main()
	Sales_data A;
	print(std::cout,A) << std::endl;
	
	Sales_data B("bookB");
	print(std::cout,B) << std::endl;
	
	Sales_data C("bookC",12,3.0);
	print(std::cout,C) << std::endl;
	
	Sales_data D(std::cin);
	print(std::cout,D) << std::endl;
	
	return 0;

7.13 使用istream构造函数重写第229页的程序。

#include <iostream>
#include <string>


struct Sales_data;
std::istream &read(std::istream&,Sales_data&);

struct Sales_data 
	Sales_data() = default;
	Sales_data(const std::string &s):bookNo(s)
	Sales_data(const std::string &s,unsigned u,double p)
		:bookNo(s),units_sold(u),revenue(u*p)
	Sales_data(std::istream &is)read(is,*this);
	
	std::string bookNo;
	unsigned units_sold = 0;
	double revenue = 0.0;
	
	Sales_data& combine(const Sales_data &rhs);
	std::string isbn()constreturn bookNo;
	double avg_price()const;
;


double Sales_data::avg_price()const
	return units_sold?(revenue/units_sold):0;


Sales_data& Sales_data::combine(const Sales_data &rhs)
	units_sold += rhsC++ Primer 0x0B 练习题解

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