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目录

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本章小结

       面向对象编程强调的是程序如何表示数据。使用OOP方法解决编程问题的第一步是根据它程序之间的接口来描述数据，从而指定如何使用数据。然后，设计一个类来实现该接口。一般来说，私有数据成员存储信息，公有成员函数（又称为方法）提供访问数据的唯一途径。类将数据和方法组合成一个单元，其私有性实现数据隐藏。        通常，将类声明分成两部分组成，这两部分通常保存在不冋的文件中。类声明（包括由函数原型表示的方法）应放到头文件中。定义成员函数的源代码放在方法文件中。这样便将接口描述与实现细节分开了。 从理论上说，只需知道公有接口就可以使用类。当然，可以查看实现方法（除非只提供了编译形式），但程序不应依赖于其实现细节，如知道某个值被存储为int。只要程序和  类只通过定义接口的方法进行通信，程序员就可以随意地对任何部分做独立的改进，而不必担心这样做会导致意外的不良影响。        类是用户定义的类型，对象是类的实例。这意味着对象是这种类型的变量，例如由new按类描述分配的内存C++试图让用户定义的类型尽可能与标准类型类似，因此可以声明对象、指向对象的指针和对象数组。可以按值传递对象、将对象作为函数返回值、将一个对象赋给同类型的另一个对象。如果提供了构造函数，则在创建对象时，可以初始化对象。如果提供了析构函数方法，则在对象消亡后，程序将执行该函数。        每个对象都存储自己的数据，而共享类方法。如果mr_object是对象名，try_me()是成员函数，则可以使用成员运算符句点调用成员函数：mr_object.try_me()。在OOP中，这种函数调用被称为将try_me消息发送给mr_object对象。在try_me()方法中引用类数据成员时，将使用mr_object对象相应的数据成员。同样，函数调用i_objet.try_me()将访问i_object对象的数据成员。       如果希望成员函数对多个对象进行操作，可以将额外的对象作为参数传递给它。如果方法需要显式地引用调用它的对象，则可以使用this指针。由于this指针被设置为调用对象的地址，因此*this是该对象的别名。        类很适合用于描述ADT(abstract data type,抽象数据类型)。公有成员函数接口提供了 ADT描述的服务，类的私有部分和类方法的代码提供了实现，这些实现对类的客户隐藏。

程序清单

创建一个Stock类（version 1）

10.1 stock00.h  Stock类的声明

//stock00.h -- Stock class interface//version 00#ifndef STOCK00_H_#define STOCK00_H_#include "stdafx.h"#include
   
    class Stock //class declaration{private:	std::string company;	long shares;	double share_val;	double total_val;	void set_tot()	{		total_val = shares * share_val;	}public:	void acquire(const std::string & co, long n, double pr);	void buy(long num, double price);	void sell(long num, double price);	void update(double price);	void show();}; //note semicolon at the end#endif // !STOCK00_H_
   

 10.2 stock00.cpp  Stock类方法的实现

//stock00.cpp -- implementing the Stock class//version 00#include "stdafx.h"#include "stock00.h"#include
   
    using namespace std;void Stock::acquire(const std::string & co, long n, double pr){	company = co;	if (n < 0)	{		cout << "Number of shares can't be negative; " << company << " shares set to 0.\n";		shares = 0;	}	else		shares = n;	share_val = pr;	set_tot();}void Stock::buy(long num, double price){	if (num < 0)	{		cout << "Number of shares purchased can't be negative. Transaction is aborted.\n";	}	else	{		shares += num;		share_val = price;		set_tot();	}}void Stock::sell(long num, double price){	if (num < 0)	{		cout << "Number of shares sold can't be negative. Transaction is aborted.\n";	}	else if (num > shares)	{		cout << "You can't sell more than you have! Transaction is aborted.\n";	}	else	{		shares -= num;		share_val = price;		set_tot();	}}void Stock::update(double price){	share_val = price;	set_tot();}void Stock::show(){	cout << "Company: " << company;	cout << "  Shares: " << shares << endl;	cout << "    Share Price: $" << share_val << endl;	cout << "    Total Worth: $" << total_val << endl;}
   

 10.3 usestock0.cpp  使用Stock类

// usestock0.cpp -- the client program// compile with stock00.cpp#include "stdafx.h"#include "stock00.h"#include
   
    int main(){	Stock fluffy_the_cat;	fluffy_the_cat.acquire("NanoSmart", 20, 12.50);	fluffy_the_cat.show();	fluffy_the_cat.buy(15, 18.125);	fluffy_the_cat.show();	fluffy_the_cat.sell(400, 20.00);	fluffy_the_cat.show();	fluffy_the_cat.buy(300000, 40.125);	fluffy_the_cat.show();	fluffy_the_cat.sell(300000, 0.125);	fluffy_the_cat.show();	return 0;}
   

创建一个Stock类（version 2），增加了构造函数和析构函数

10.4 stock10.h  stock类的声明，添加了构造函数和析构函数

//stock10.h -- Stock class declaration with constructors destructor added//version 10#ifndef STOCK10_H_#define STOCK10_H_#include "stdafx.h"#include
   
    class Stock //class declaration{private:	std::string company;	long shares;	double share_val;	double total_val;	void set_tot()	{		total_val = shares * share_val;	}public:	Stock();//default constructor	Stock(const std::string & co, long n = 0, double pr = 0.0);	~Stock();//noisy destructor	void buy(long num, double price);	void sell(long num, double price);	void update(double price);	void show();}; //note semicolon at the end#endif // !STOCK10_H_
   

 10.5 stock10.cpp  stock类方法的实现，在这个版本中输出精度得到了统一

//stock10.cpp -- Stock class declaration with constructors destructor added//version 10#include "stdafx.h"#include "stock10.h"#include
   
    using namespace std;//constructors (verbose versions)Stock::Stock(){	cout << "Default constructor called\n";	company = "no name";	shares = 0;	share_val = 0.0;	total_val = 0.0;}Stock::Stock(const std::string & co, long n /* = 0 */, double pr /* = 0.0 */){	cout << "Constructor using " << co << " called\n";	company = co;	if (n < 0)	{		cout << "Number of shares can't be negative: " << company << " shares set to 0.\n";		shares = 0;	}	else		shares = n;	share_val = pr;	set_tot();}//class destructorStock::~Stock(){	cout << "Bye. " << company << "!\n";}//other methodsvoid Stock::buy(long num, double price){	if (num < 0)	{		cout << "Number of shares purchased can't be negative. Transaction is aborted.\n";	}	else	{		shares += num;		share_val = price;		set_tot();	}}void Stock::sell(long num, double price){	if (num < 0)	{		cout << "Number of shares sold can't be negative. Transaction is aborted.\n";	}	else if (num > shares)	{		cout << "You can't sell more than you have! Transaction is aborted.\n";	}	else	{		shares -= num;		share_val = price;		set_tot();	}}void Stock::update(double price){	share_val = price;	set_tot();}void Stock::show(){	ios_base::fmtflags orig = cout.setf(ios_base::fixed, ios_base::floatfield);	streamsize prec = cout.precision(3);//set format to #.###	cout << "Company: " << company;	cout << "  Shares: " << shares << endl;	cout << "    Share Price: $" << share_val << endl;	cout.precision(2);//set format to #.##	cout << "    Total Worth: $" << total_val << endl;	//restore original format	cout.setf(orig, ios_base::floatfield);	cout.precision(prec);}
   

10.6 usestock1.cpp  使用stock类

//usestock1.cpp -- using the Stock class//compile with stock10.cpp#include "stdafx.h"#include "stock10.h"#include
   
    int main(){	using namespace std;	cout << "Using constructors to create new objects\n";	Stock stock1("NanoSmart", 12, 20.0);	stock1.show();	Stock stock2 = Stock("Boffo Objects", 2, 2.0);	stock2.show();	cout << "Assing stock1 to stock2:\n";	stock2 = stock1;	cout << "Listing stock1 and stock2:\n";	stock1.show();	stock2.show();	cout << "Using a constructor to reset an object\n";	stock1 = Stock("Nifty Foods", 10, 50.0);	cout << "Revised stock1:\n";	stock1.show();	cout << "Done\n";	return 0;}
   

创建一个Stock类（version 3），使用了*this指针

 10.7 stock20.h 添加了新方法topval()并使用了*this指针

//stock20.h -- sugmented version#ifndef STOCK20_H_#define STOCK20_H_#include 
   
    class Stock{private:	std::string company;	int shares;	double share_val;	double total_val;	void set_tot()	{		total_val = shares * share_val;	}public:	Stock();	Stock(const std::string & co, long n = 0, double pr = 0.0);	~Stock();	void buy(long num, double price);	void sell(long num, double price);	void update(double price);	void show() const;	const Stock & topval(const Stock & s) const;};#endif // !STOCK20_H_
   

10.8 Stock类的实现，使用了*this指针 

//stock20.cpp -- augmented version//version 20#include "stdafx.h"#include "stock20.h"#include 
   
    using namespace std;//constructors (verbose versions)Stock::Stock(){	company = "no name";	shares = 0;	share_val = 0.0;	total_val = 0.0;}Stock::Stock(const std::string & co, long n, double pr){	company = co;	if (n < 0)	{		cout << "Number of shares can't be negative: " << company << " shares set to 0.\n";		shares = 0;	}	else		shares = n;	share_val = pr;	set_tot();}//class destructorStock::~Stock(){}//other methodsvoid Stock::buy(long num, double price){	if (num < 0)	{		cout << "Number of shares purchased can't be negative. Transaction is aborted.\n";	}	else	{		shares += num;		share_val = price;		set_tot();	}}void Stock::sell(long num, double price){	if (num < 0)	{		cout << "Number of shares sold can't be negative. Transaction is aborted.\n";	}	else if (num > shares)	{		cout << "You can't sell more than you have! Transaction is aborted.\n";	}	else	{		shares -= num;		share_val = price;		set_tot();	}}void Stock::update(double price){	share_val = price;	set_tot();}void Stock::show() const{	ios_base::fmtflags orig = cout.setf(ios_base::fixed, ios_base::floatfield);	streamsize prec = cout.precision(3);//set format to #.###	cout << "Company: " << company;	cout << "  Shares: " << shares << endl;	cout << "    Share Price: $" << share_val << endl;	cout.precision(2);//set format to #.##	cout << "    Total Worth: $" << total_val << endl;	//restore original format	cout.setf(orig, ios_base::floatfield);	cout.precision(prec);}const Stock & Stock::topval(const Stock & s) const {	if (s.total_val > total_val)		return s;	else		return *this;}
   

10.9 使用stock类建立对象数组 

//usestock2.cpp -- using the Stock class//compile with stock20.cpp#include "stdafx.h"#include "stock20.h"#include 
   
    const int STKS = 4;int main(){	using namespace std;	Stock stocks[STKS] =	{		Stock("NamoSmart",12,20.0),		Stock("Boffo Objects",200,2.0),		Stock("Monolithic Obelisks",130,3.25),		Stock("Fleep Enterprises",60,6.5)	};	cout << "Stock holdings:\n";	int st;	for (st = 0; st < STKS; st++)		stocks[st].show();	const Stock *top = &stocks[0];	for (st = 1; st < STKS; st++)		top = &top->topval(stocks[st]);	cout << "\nMost valuable holding:\n";	top->show();	return 0;}
   

创建一个抽象数据类型(ADT)--stack类

 10.10 stack.h stack类的声明，stack(栈)是一种抽象数据类型(ADT)

//stack.h -- class definition for the stack ADT#ifndef STACK_H_#define STACK_H_typedef unsigned long Item;class  Stack{private:	enum { MAX = 10 };	Item items[MAX];	int top;public:	Stack();	bool isempty() const;	bool isfull() const;	bool push(const Item & item);	bool pop(Item & item);};#endif

10.11  stack类方法的实现

//stack.cpp -- Stack member functions#include "stdafx.h"#include "stack.h"Stack::Stack(){	top = 0;}bool Stack::isempty() const {	return top == 0;}bool Stack::isfull() const{	return top == MAX;}bool Stack::push(const Item &item){	if (top < MAX)	{		items[top++] = item;		return true;	}	else		return false;}bool Stack::pop(Item & item){	if (top > 0)	{		item = items[--top];		return true;	}	else		return false;}

10.12 使用stack类

//stacker.cpp -- testing the Stack class#include "stdafx.h"#include "stack.h"#include 
   
    #include 
    
     int main(){	using namespace std;	Stack st;	char ch;	unsigned long po;	cout << "Please enter A to add a purchase order,\nP to process a PO ,or Q to quit.\n";	while (cin >> ch && toupper(ch) != 'Q')	{		while (cin.get() != '\n')			continue;		if (!isalpha(ch))		{			cout << '\a';			continue;		}		switch (ch)		{		case 'A':		case 'a': 			cout << "Enter a PO number to add: ";			cin >> po;			if (st.isfull())				cout << "stack already full\n";			else				st.push(po);			break;		case 'P':		case 'p':			if (st.isempty())				cout << "stack already empty\n";			else			{				st.pop(po);				cout << "PO #" << po << " popped\n";			}			break;		}		cout << "Please enter A to add a purchase order,\n"			<< "p to process a PO, or Q to quit.\n";	}	cout << "Bye\n";	return 0;}
    
   

课后编程习题答案

习题1

//bankaccount.h#ifndef BANKACCOUNT_H_#define BANKACCOUNT_H_#include 
   
    class BankAccount{ private:    std::string name;    std::string acctnum;    double balance;public:    BankAccount(const std::string & client,    const std::string & num, double bal=0.0);    void show() const;    void deposit(double cash);    void withdraw(double cash);};#endif//bankaccount.cpp#include 
    
     #include "bankaccount.h"BankAccount::BankAccount(const std::string & client, const std::string & num, double bal){     name = client;    acctnum = num;    balance = bal;} void BankAccount::show()const{     using std::cout;    using std::endl;    cout << "Client: " << name << endl;    cout << "Account Number: " << acctnum << endl;    cout << "Balance: " << balance << endl;} void BankAccount::deposit(double cash){     if (cash >= 0)        balance += cash;    else        std::cout << "Illegal transaction attempted";} void BankAccount::withdraw(double cash){     if (cash < 0)        std::cout << "Illegal transaction attempted";    else if (cash <= balance)        balance -=cash;    else        std::cout << "Request denied due to insufficient funds.\n";} //main.cpp#include 
     
      #include "bankaccount.h"int main(){    BankAccount ba("Kermit", "    croak322", 123.00);    ba.show();    ba.deposit(20);    ba.show();    ba.withdraw(300);    ba.show();    ba.withdraw(23);    ba.show();    return 0;}
     
    
   

习题2

//person.h#ifndef PERSON_H_#define PERSON_H_#include 
   
    class Person{ private:    static const int LIMIT=25;    std::string lname;    char fname[LIMIT];public:    Person() {lname=""; fname[0]='\0';} //#1    Person(const std::string &ln, const char * fn="Heyyou"); //#2    // the following methods display lname and fname    void Show() const; // firstname lastname format    void FormalShow() const; // lastname, firstname format};#endif//person.cpp#include 
    
     #include 
     
      #include "person.h"Person::Person(const std::string &ln, const char * fn){     lname = ln;    strcpy(fname, fn);} void Person::Show() const{     using std::cout;    using std::endl;    cout << "The people's name is " << fname << " "<< lname << endl;}void Person::FormalShow() const{    using std::cout;    using std::endl;    cout << "The people's name is " << lname << ", "<< fname <
      
       #include "person.h"int main(){    using std::cout;    using std::endl;    Person one;    Person two("Smythecraft");    Person three("Dimwiddy", "Sam");    one.Show();    one.FormalShow();    cout << endl;    two.Show();    two.FormalShow();    cout << endl;    three.Show();    three.FormalShow();    cout << endl;    return 0;}
      
     
    
   

习题3

//golf.h#ifndef GOLF_H_#define GOLF_H_class Golf{private:    static const int Len = 40;    char fullname[Len];    int handicap;public:    Golf();    Golf(const char * name, int hc);    const Golf & setgolf(const Golf & g);    void showgolf() const;};#endif//golf.cpp#include 
   
    #include 
    
     #include "golf.h"Golf::Golf(){    strcpy(fullname, "No Name");    handicap = 0;} Golf::Golf(const char *name, int hc){    strcpy(fullname, name);    handicap = hc;} const Golf &Golf::setgolf(const Golf &g){    strcpy(fullname, g.fullname);    handicap = g.handicap;    return *this;} void Golf::showgolf() const{     std::cout << "Golfer: " << fullname << "\n";    std::cout << "Handicap: " << handicap << "\n\n";} //main#include 
     
      #include "golf.h"int main(){    Golf golger1("Ann Birdfree", 5);    golger1.showgolf();    Golf golger2;    golger2.setgolf(golger1);    golger2.showgolf();    return 0;}
     
    
   

习题4

//sale.h#ifndef SALE_H_#define SALE_H_namespace SALES{     const int QUARTERS = 4;    class Sales    {    private:        double sales[QUARTERS];        double average;        double max;        double min;    public:        Sales(); // default constructor        // copies the lesser of 4 or n items from the array ar        // to the sales member of s and computes and stores the        // average, maximum, and minimum values of the entered items;        // remaining elements of sales, if any, set to 0        Sales(const double ar[], int n);        // gathers sales for 4 quarters interactively, stores them        // in the sales member of s and computes and stores the        // average, maximum, and minimum values        void setSales();        // display all information in structure s        void showSales() const;    };} #endif//sale.cpp#include 
   
    #include "sale.h"namespace SALES{     using std::cout;    using std::cin;    using std::endl;    static double calaverage(double arr[], unsigned arrSize)    {         double sum = 0;    for (int i=0; i
    
      arr[i])        min = arr[i];        }        return min;    }     Sales::Sales()    {         min = 0;        max = 0;        average = 0;        for (int i = 0; i < QUARTERS; i++)            sales[i] =0;    }     Sales::Sales(const double ar[], int n)    {         unsigned times = n < QUARTERS ? (unsigned)n:QUARTERS;        for (int i=0; i
     
      > sales[i];        }        *this = Sales(sales, QUARTERS);    }    void Sales::showSales() const    {         cout << "sales: ";        for (int i=0; i
      
       #include "sale.h"using namespace std;int main (){     using namespace SALES;    double salesList[] = {12.2, 11.16, 10.61, 16.24, 11.53};    Sales salesBook(salesList,    sizeof(salesList)/sizeof(salesList[0]));    salesBook.showSales();    Sales salesPen;    salesPen.setSales();    salesPen.showSales();    return 0;}
      
     
    
   

习题5

//stack.h#ifndef STACK_H_#define STACK_H_struct customer{    char fullname[35];    double payment;};typedef customer Item;class Stack{private:    enum {MAX = 10};    Item items[MAX];    int top;public:    Stack();    bool isempty() const;    bool isfull() const;    // push() returns false if stack already is full, true otherwise    bool push(const Item & item); // add item to stack    // pop() returns false if stack already is empty, true otherwise    bool pop(Item & item); // pop top into item};#endif//stack.cpp#include 
   
    #include "stack.h"Stack::Stack(){     top = 0;}bool Stack::isempty() const{     return top == 0;} bool Stack::isfull() const{     return top == MAX;} bool Stack::push(const Item &item){     if (top 
    
      0)    {         item = items[--top];        return true;    }     else        return false;} //main.cpp#include 
     
      #include 
      
       #include "stack.h"void get_customer(customer & cu);int main(){     using namespace std;    Stack st;    customer temp;    double payment = 0;    char ch;    cout << "Please enter A to add a customer,\n" << "P to process a customer, and Q to quit.\n";    while (cin >> ch && (ch = toupper(ch)) != 'Q')    {         while (cin.get() != '\n')            continue;        if (ch != 'A' && ch != 'P')        {             cout << "Please respond A, P or Q: ";            continue;        }          switch (ch)         {             case 'A':                if (st.isfull())                    cout << "stack already full\n";                else                {                    get_customer(temp);                    st.push(temp);                }                 break;            case 'P':                if (st.isempty())                    cout << "stack is empty\n";                else                {                     st.pop(temp);                    payment += temp.payment;                    cout << temp.fullname << " processed. ";                    cout << "Payments now total $" << payment << "\n";                }                 break;        }        cout << "Please enter A to add a customer,\n" << "P to process a customer, and Q to quit.\n";    }     cout << "Done!\n";    return 0;}void get_customer(customer &cu){     using namespace std;    cout << "Enter customer name: ";    cin.getline(cu.fullname, 35);    cout << "Enter customer payment: ";    cin >> cu.payment;    while (cin.get() != '\n')    continue;}
      
     
    
   

习题6

//move.h#ifndef MOVE_H_#define MOVE_H_class Move{ private:    double x;    double y;public:    Move(double a = 0, double b = 0);    void showMove() const;    Move add(const Move & m) const;    //this function adds x of m to x of invoking object to get new x    //add y of m to y of invoking object to get new y, creates a new    //move object initialized to new x,y values and returns it    void reset(double a = 0,double b = 0);};#endif//move.cpp#include 
   
    #include "move.h"Move::Move(double a, double b){    x = a;    y = b;} void Move::showMove() const{     std::cout << "x = " << x << ", y = " << y << "\n";} Move Move::add(const Move &m) const{     Move temp;    temp.x = x + m.x;    temp.y = y + m.y;    return temp;} void Move::reset(double a, double b){    x = a;    y = b;} //main#include 
    
     #include "move.h"int main(){     using std::cout;    using std::endl;    Move move1(4,5);    Move move2(2,1);    Move move3;    cout << "The number in move1 is:\n";    move1.showMove();    cout << "The number in move2 is:\n";    move2.showMove();    move3 = move2.add(move1);    cout << "The number in move3 is :\n";    move3.showMove();    cout << "move1+move2, now move2's number is :\n";    move2.showMove();    cout << "After move1 + move2,now move1's number is :\n";    move1.showMove();    move1.reset();    cout << "After reset move1,now move1's number is:\n";    move1.showMove();    return 0;}
    
   

习题7

//plorg.cpp#ifndef PLORG_H_#define PLORG_H_class Plorg{ private:    char name[20];    int CI;public:    Plorg();    Plorg(char * na, int n = 50);    void resetCI(int n);    void showplorg() const;};#endif//plorg.cpp#include 
   
    #include 
    
     #include "plorg.h"Plorg::Plorg(){     strcpy(name, "Plorga");    CI = 0;} Plorg::Plorg(char *na, int n){     strcpy(name, na);    CI = n;} void Plorg::resetCI(int n){     CI = n;} void Plorg::showplorg() const{     std::cout << " The plorg's name is " << name << "\n" <<"The CI is "<< CI <
     
      #include "plorg.h"int main(){     using namespace std;    Plorg plorg1;    plorg1.showplorg();    Plorg plorg2("heyyroup", 31);    plorg2.showplorg();    plorg1.resetCI(41);    plorg1.showplorg();    return 0;}
     
    
   

习题8

//list.h#ifndef LIST_H_#define LIST_H_const int TSIZE = 50;struct film{     char title[TSIZE];    int rating;};typedef struct film Item;const int LISTMAX = 10;class List{ private:    Item items[LISTMAX];    int count;public:    List();    bool isempty();    bool isfull();    int itemcount();    bool additem(Item item);    void visit(void (*pf)(Item &));};#endif//list.cpp#include "list.h"List::List(){ count = 0;} bool List::isempty(){     return count == 0;} bool List::isfull(){     return count == LISTMAX;} int List::itemcount(){    return count;} bool List::additem(Item item){     if (count == LISTMAX)        return false;    else        items[count++] = item;    return true;} void List::visit(void (*pf)(Item &)){     for (int i=0; i
   
    #include 
    
     #include "list.h"void showfilm(Item & item);int main(){     using namespace std;    List movies;    Item temp;    if (movies.isfull())    {         cout << "No more room in list! Bye!\n";        exit(1);    }     cout << "Enter first movie title:\n";    while (cin.getline(temp.title, TSIZE) && temp.title[0] != '\0')    {         cout << "Enter your rating <1-10>: ";        cin >> temp.rating;        while (cin.get() != '\n')            continue;        if (movies.additem(temp) == false)        {                cout << "List already is full!\n";            break;        }         if (movies.isfull())        {             cout << "You have filled the list.\n";            break;        }         cout << "Enter next movie title (empty line to stop):\n";    }     if (movies.isempty())        cout << "No data entered.";    else    {         cout << "Here is the movie list:\n";        movies.visit(showfilm);    }     cout << "Bye!\n";    return 0;} void showfilm(Item &item){     std::cout << "Movie: "<< item.title << "Rating: "<< item.rating << std::endl;}
    
   

 

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