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C++Primer Plus笔记——第十一章 使用类及课后编程练习答案
发布日期：2021-06-29 01:51:01 浏览次数：2 分类：技术文章

本文共 38603 字，大约阅读时间需要 128 分钟。

目录

本章小结

      本章介绍了定义和使用类的许多重要方面，其中的一些内容可能比较难理解，但随着实践经验的不断增加，您将逐步掌握他们。

       一般来说，访问私有类成员的唯一方法是使用类方法。C++使用友元函数来避幵这种限制。要让函数为友元，需要在类声明中声明该函数，并在声明前加上关键字friend。

       C++扩展了对运算符的重载，允许自定义特殊的运算符函数，这种函数描述了特定的运算符与类之间的关系。 运算符函数可以是类成员函数，也可以是友元函数（有一些运算符函数只能是类成员函数)。要调用运算符函数， 可以直接调用该函数，也可以以通常的句法使用被重载的运算符。对于运算符op,其运算符函数的格式如下：

        operatorop(argument-list)

       argument-list表示该运算符的操作数。如果运算符函数是类成员函数，则第一个操作数是调用对象， 它不在argument-list中。例如，本章通过为Vector类定义operator+()成员函数重载了加法。如果up、right 和result都是Vector对象，则可以使用下面的任何一条语句来调用矢量加法：

       result = up.operator+(right)；

       result = up + right；

       在第二条语句中，由于操作数up和right的类型都是Vector,因此C++将使用Vector的加法定义。

       当运算符函数是成员函数时，则第一个操作数将是调用该函数的对象.例如，在前面的语句中，up对象是调用函数的对象。定义运算符函数时，如果要使其第一个操作数不是类对象，则必须使用友元函数。 这样就可以将操作数按所需的顺序传递给函数了。

       最常见的运算符重载任务之一是定义<<运算符，使之可与cout —起使用，来显示对象的内容。要让ostream对象成为第一个操作数，需要将运算符函数定义为友元：要使重新定义的运算符能与其自身拼接， 需要将返回类型声明为ostream&。下面的通用格式能够满足这种要求：

ostream & operator<< (ostream & os, const c_name & obj)

{
       os << ... ；    // display object contents
        return os;

}

       然而，如果类包含这样的方法，它返回需要显示的数据成员的值，则可以使用这些方法，无需在 operator<<()中直接访问这些成员。这种情况下：函数不必(也不应是)友元。

        C++允许指定在类和基本类型之间进转换的方式。首先，任何接受唯一一个参数的构造函数都可被用作转换函数，将类型与该参数相同的值转换为类。如果将类型与该参数相同的值赋给对象，则C++将自动调用该构造函数。例如，假设有一个String类，它包含一个将char*值作为其唯一参数的构造函数，那么如果bean是String对象，则可以使用下面的语句：

          bean =  "pinto"; //If converts type char * to type String

        然而，如果在该构造函数的声明前加上了关键宁•explicit，则该构造函数将只能用于显式转换：

         bean = String("pinto")；    // converts type char * to type String explicitly

       要将类对象转换为其他类型，必须定义转换函数，指出如何进行这种转换。转换函数必须是成员函数。 将类对象转换为typcName类型的转换函数的原型如下：

          operator typeName()；

        注意，转换函数没有返回类型、没有参数，但必须返回转换后的值（虽然没有声明返回类型）。例如， 下面是将Vector转换为double类型的函数：

        Vector::operator doublet)

       {

              return a_double_value；
       }

       经验表明，最好不要依赖于这种隐式转换函数。

      您可能已经注意到了，与简单的C-风格结构相比，使用类时，必须更谨慎、更小心，但作为补偿，它们为我们完成的工作也更多。

程序清单

定义一个Time类(Version 1)，加法用函数实现

11.1 mytime0.h Time类的声明，加法用Sum()时间

//mytime0.h -- Time class before operator overloading#ifndef MYTIME0_H_#define MYTIME0_H_class Time{private:	int hours;	int minutes;public:	Time();	Time(int h, int m = 0);	void AddMin(int m);	void AddHr(int h);	void Reset(int h = 0, int m = 0);	Time Sum(const Time &t)const;	void Show() const;};#endif // !MYTIME0_H_

11.2 mytime0.cpp 类方法的定义

//mytime0.cpp -- implementing Time methods#include 
   
    #include "mytime0.h"Time::Time(){	hours = minutes = 0;}Time::Time(int h, int m /* = 0 */){	hours = h;	minutes = m;}void Time::AddMin(int m){	minutes += m;	hours += minutes / 60;	minutes %= 60;}void Time::AddHr(int h){	hours += h;}void Time::Reset(int h /* = 0 */, int m /* = 0 */){	hours = h;	minutes = m;}Time Time::Sum(const Time &t)const{	Time sum;	sum.minutes = minutes + t.minutes;	sum.hours = hours + t.hours + sum.minutes / 60;	sum.minutes %= 60;	return sum;}void Time::Show()const {	std::cout << hours << " hours, " << minutes << " minutes";}

11.3 usetime0.cpp 使用Time类

//usetime0.cpp -- using the first draft of the Time class//compile usetime0.cpp and mytime0.cpp together#include 
   
    #include "mytime0.h"int usetime0(){	using namespace std;	Time planning;	Time coding(2, 40);	Time fixing(5, 55);	Time total;	cout << "planning time = ";	planning.Show();	cout << endl;	cout << "coding time = ";	coding.Show();	cout << endl;	cout << "fixing time = ";	fixing.Show();	cout << endl;	total = coding.Sum(fixing);	cout << "coding.Sum(fixing) = ";	total.Show();	cout << endl;	return 0;}

定义一个Time类(Version 2)，加法用运算符重载实现

11.4 mytime1.h Time类的声明， 加法用运算符重载来实现

//mytime1.h -- Time class before operator overloading#ifndef MYTIME1_H_#define MYTIME1_H_class Time{private:	int hours;	int minutes;public:	Time();	Time(int h, int m = 0);	void AddMin(int m);	void AddHr(int h);	void Reset(int h = 0, int m = 0);	Time operator + (const Time &t) const;	void Show() const;};#endif // !MYTIME1_H_

11.5 mytime1.cpp Time类方法的定义

//mytime1.cpp -- implementing Time methods#include 
   
    #include "mytime1.h"Time::Time(){	hours = minutes = 0;}Time::Time(int h, int m /* = 0 */){	hours = h;	minutes = m;}void Time::AddMin(int m){	minutes += m;	hours += minutes / 60;	minutes %= 60;}void Time::AddHr(int h){	hours += h;}void Time::Reset(int h /* = 0 */, int m /* = 0 */){	hours = h;	minutes = m;}Time Time::operator+(const Time &t)const{	Time sum;	sum.minutes = minutes + t.minutes;	sum.hours = hours + t.hours + sum.minutes / 60;	sum.minutes %= 60;	return sum;}void Time::Show()const{	std::cout << hours << " hours, " << minutes << " minutes";}

11.6 使用Time类

//usetime1.cpp -- using the second draft of the Time class//compile usetime1.cpp and mytime0.cpp together#include 
   
    #include "mytime1.h"int main(){	using namespace std;	Time planning;	Time coding(2, 40);	Time fixing(5, 55);	Time total;	cout << "planning time = ";	planning.Show();	cout << endl;	cout << "coding time = ";	coding.Show();	cout << endl;	cout << "fixing time = ";	fixing.Show();	cout << endl;	total = coding + fixing;	cout << "coding + fixing = ";	total.Show();	cout << endl;	Time morefixing(3, 28);	cout << "more fixing time = ";	morefixing.Show();	cout << endl;	total = morefixing.operator+(total);	//function notation	cout << "morefixing.operator+(total) = ";	total.Show();	cout << endl;	return 0;}

定义一个Time类(Version 3)，加法，减法及乘法用运算符重载实现

11.7 mytime2.h Time类的声明

//mytime2.h -- Time class before operator overloading#ifndef MYTIME2_H_#define MYTIME2_H_class Time{private:	int hours;	int minutes;public:	Time();	Time(int h, int m = 0);	void AddMin(int m);	void AddHr(int h);	void Reset(int h = 0, int m = 0);	Time operator + (const Time &t) const;	Time operator - (const Time &t) const;	Time operator * (double n) const;	void Show() const;};#endif // !MYTIME2_H_

11.8 mytime2.cpp Time类方法的定义

//mytime2.cpp -- implementing Time methods#include 
   
    #include "mytime2.h"Time::Time(){	hours = minutes = 0;}Time::Time(int h, int m /* = 0 */){	hours = h;	minutes = m;}void Time::AddMin(int m){	minutes += m;	hours += minutes / 60;	minutes %= 60;}void Time::AddHr(int h){	hours += h;}void Time::Reset(int h /* = 0 */, int m /* = 0 */){	hours = h;	minutes = m;}Time Time::operator+(const Time &t)const{	Time sum;	sum.minutes = minutes + t.minutes;	sum.hours = hours + t.hours + sum.minutes / 60;	sum.minutes %= 60;	return sum;}Time Time::operator-(const Time &t)const{	Time diff;	int tot1, tot2;	tot1 = t.minutes + 60 * t.hours;	tot2 = minutes + 60 * hours;	diff.minutes = (tot2 - tot1) % 60;	diff.hours = (tot2 - tot1) / 60;	return diff;}Time Time::operator*(double mult)const{	Time result;	long totalminutes = hours * mult * 60 + minutes * mult;	result.hours = totalminutes / 60;	result.minutes = totalminutes % 60;	return result;}void Time::Show()const{	std::cout << hours << " hours, " << minutes << " minutes";}

11.9 usetime2.cpp 使用Time类

//usetime2.cpp -- using the third draft of the Time class//compile usetime2.cpp and mytime2.cpp together#include 
   
    #include "mytime2.h"int main(){	using namespace std;	Time weeding(4, 35);	Time waxing(2, 47);	Time total;	Time diff;	Time adjusted;	cout << "weeding time = ";	weeding.Show();	cout << endl;	cout << "waxing time = ";	waxing.Show();	cout << endl;	total = weeding + waxing;	cout << "total work time = ";	total.Show();	cout << endl;	diff = weeding - waxing;	cout << "weeding time - waxing time = ";	diff.Show();	cout << endl;	adjusted = total * 1.5;	//function notation	cout << "adjusted work time = ";	adjusted.Show();	cout << endl;	return 0;}

定义一个Time类(Version 4)，乘法用友元运算符重载实现

11.10 mytime3.h Time类的声明

//mytime3.h -- Time class with friends#ifndef MYTIME3_H_#define MYTIME3_H_#include 
   
    class Time{private:	int hours;	int minutes;public:	Time();	Time(int h, int m = 0);	void AddMin(int m);	void AddHr(int h);	void Reset(int h = 0, int m = 0);	Time operator + (const Time &t) const;	Time operator - (const Time &t) const;	Time operator * (double n) const;	friend Time operator * (double m, const Time & t)	{		return t * m;	}	friend std::ostream & operator << (std::ostream & os, const Time & t);};#endif // !MYTIME3_H_

11.11 mytime3.cpp Time类方法的定义

//mytime3.cpp -- implementing Time methods#include "mytime3.h"Time::Time(){	hours = minutes = 0;}Time::Time(int h, int m /* = 0 */){	hours = h;	minutes = m;}void Time::AddMin(int m){	minutes += m;	hours += minutes / 60;	minutes %= 60;}void Time::AddHr(int h){	hours += h;}void Time::Reset(int h /* = 0 */, int m /* = 0 */){	hours = h;	minutes = m;}Time Time::operator+(const Time &t)const{	Time sum;	sum.minutes = minutes + t.minutes;	sum.hours = hours + t.hours + sum.minutes / 60;	sum.minutes %= 60;	return sum;}Time Time::operator-(const Time &t)const{	Time diff;	int tot1, tot2;	tot1 = t.minutes + 60 * t.hours;	tot2 = minutes + 60 * hours;	diff.minutes = (tot2 - tot1) % 60;	diff.hours = (tot2 - tot1) / 60;	return diff;}Time Time::operator*(double mult)const{	Time result;	long totalminutes = hours * mult * 60 + minutes * mult;	result.hours = totalminutes / 60;	result.minutes = totalminutes % 60;	return result;}std::ostream & operator << (std::ostream & os, const Time & t){	os << t.hours << " hours, " << t.minutes << " minutes";	return os;}

11.12 使用Time类

//usetime3.cpp -- using the fourth draft of the Time class//compile usetime3.cpp and mytime3.cpp together#include 
   
    #include "mytime3.h"int main(){	using namespace std;		Time aida(3, 35);	Time tosca(2, 48);	Time temp;	cout << "Aida and Tosca:\n";	cout << aida << "; " << tosca << endl;	temp = aida + tosca;	cout << "Aida + Tosca: " << temp << endl;	temp = aida * 1.17;	cout << "Aida * 1.17: " << temp << endl;	cout << "10.0 * Tosca: " << 10.0 * tosca << endl;	return 0;}

定义一个矢量类 Vector

11.13 vector.h Vector类的声明

//vector.h -- Vector class with <<, mode state#ifndef VECTOR_H_#define VECTOR_H_#include 
   
    namespace VECTOR{	class Vector	{	public:		enum Mode {RECT, POL};	private:		double x;		double y;		double mag;		double ang;		Mode mode;		void set_mag();		void set_ang();		void set_x();		void set_y();	public:		Vector();		Vector(double n1, double n2, Mode form = RECT);		void reset(double n1, double n2, Mode form = RECT);		~Vector();		double xval() const { return x; }		double yval() const { return y; }		double magval() const { return mag; }		double angval() const { return ang; }		void polar_mode();		void rect_mode();		Vector operator + (const Vector & b) const;		Vector operator - (const Vector & b) const;		Vector operator - () const;		Vector operator * (double n) const;		friend Vector operator * (double n, const Vector & a);		friend std::ostream & operator << (std::ostream & os, const Vector & v);	};}#endif // ! VECTOR_H_

11.14 vector.cpp Vector类方法的定义

//verctor.cpp -- methods for the Vector class#include 
   
    #include "vector.h"using namespace std;namespace VECTOR{	const double Rad_to_deg = 45.0 / atan(1.0);	void Vector::set_mag()	{		mag = sqrt(x*x + y * y);	}	void Vector::set_ang()	{		if (x == 0.0 && y == 0.0)			ang = 0.0;		else			ang = atan2(y, x);	}	void Vector::set_x()	{		x = mag * cos(ang);	}	void Vector::set_y()	{		y = mag * sin(ang);	}	Vector::Vector()	{		x = y = mag = ang = 0.0;		mode = RECT;	}	Vector::Vector(double n1, double n2, Mode form /* = RECT */)	{		mode = form;		if (form == RECT)		{			x = n1;			y = n2;			set_mag();			set_ang();		}		else if (form == POL)		{			mag = n1;			ang = n2 / Rad_to_deg;			set_x();			set_y();		}		else		{			cout << "Incorrect 3rd argument to Vector() -- ";			cout << "vector set to 0\n";			x = y = mag = ang = 0.0;			mode = RECT;		}	}	void Vector::reset(double n1, double n2, Mode form /* = RECT */)	{		mode = form;		if (form == RECT)		{			x = n1;			y = n2;			set_mag();			set_ang();		}		else if (form == POL)		{							mag = n1;			ang = n2 / Rad_to_deg;			set_x();			set_y();		}		else		{			cout << "Incorrect 3rd argument to Vector() -- ";			cout << "vector set to 0\n";			x = y = mag = ang = 0.0;			mode = RECT;		}	}	Vector::~Vector()	{	}	void Vector::polar_mode()	{		mode = POL;	}	void Vector::rect_mode()	{		mode = RECT;	}	Vector Vector::operator + (const Vector & b) const 	{		return Vector(x + b.x, y + b.y);	}	Vector Vector::operator - (const Vector & b) const	{		return Vector(x - b.x, y - b.y);	}	Vector Vector::operator - () const	{		return Vector(-x, -y);	}	Vector Vector::operator * (double n) const 	{		return Vector(n*x, n*y);	}	std::ostream & operator << (std::ostream & os, const Vector & v)	{		if (v.mode == Vector::RECT)			os << "(x,y) = (" << v.x << ", " << v.y << ")";		else if (v.mode == Vector::POL)		{			os << "(m,a) = (" << v.mag << ", " << v.ang * Rad_to_deg << ")";		}		else			os << "Vector object mode is invalid";		return os;	}}

11.15 randwalk.cpp 使用Vector类来模拟随机漫步

//randwalk.cpp -- using the Vector class//compile with the vect.cpp file#include 
   
    #include 
    
     #include 
     
      #include "vector.h"int main(){	using namespace std;	using VECTOR::Vector;	srand(time(0));	double direction;	Vector step;	Vector result(0.0, 0.0);	unsigned long steps = 0;	double target;	double dstep;	cout << "Enter target distance (q to quit): ";	while (cin >> target)	{		cout << "Enter step length: ";		if (!(cin >> dstep))			break;		while (result.magval() < target)		{			direction = rand() % 360;			step.reset(dstep, direction, Vector::POL);			result = result + step;			steps++;		}		cout << "After " << steps << " steps, the subject has the following location:\n" << result << endl;		result.polar_mode();		cout << " or\n" << result << endl;		cout << "Average out ward distance per step = " << result.magval() / steps << endl;		steps = 0;		result.reset(0.0, 0.0);		cout << "Enter target distance (q to quit): ";	}	cout << "Bye!\n";	cin.clear();	while (cin.get() != '\n')		continue;	return 0;}

类的自动转换和强制转换

11.16 stonewt.h

//stonewt.h -- definition for the Stonewt class#ifndef STONEWT_H_#define STONEWT_H_class Stonewt{private:	enum {Lbs_per_stn = 14};	int stone;	double pds_left;	double pounds;public:	Stonewt(double lbs);	Stonewt(int stn, double lbs);	Stonewt();	~Stonewt();	void show_lbs() const;	void show_stn() const;};#endif // !STONEWT_H_

11.17 stonewt.cpp

//stonewt.cpp -- Stonewt methods#include 
   
    #include "stonewt.h"using namespace std;Stonewt::Stonewt(double lbs){	stone = int(lbs) / Lbs_per_stn;	pds_left = int(lbs) % Lbs_per_stn + lbs - int(lbs);	pounds = lbs;}Stonewt::Stonewt(int stn, double lbs){	stone = stn;	pds_left = lbs;	pounds = stn * Lbs_per_stn + lbs;}Stonewt::Stonewt(){	stone = pounds = pds_left = 0;}Stonewt::~Stonewt(){}void Stonewt::show_stn() const{	cout << stone << " stone, " << pds_left << "pounds\n";}void Stonewt::show_lbs() const{	cout << pounds << " pounds\n";}

11.18 stone.cpp

//stone.cpp -- user-defined conversions// compile with stonewt.cpp#include 
   
    #include "stonewt.h"void display(const Stonewt & st, int n);using namespace std;int main(){	Stonewt incognito = 275;	Stonewt wolfe(285.7);	Stonewt taft(21, 8);	cout << "The celebrity weighed ";	incognito.show_stn();	cout << "The detective weighed ";	wolfe.show_stn();	cout << "The president weighed ";	taft.show_lbs();	incognito = 276.8;	taft = 325;	cout << "After dinner, the celebrity weighed ";	incognito.show_stn();	cout << "After dinner, the President weighed ";	taft.show_lbs();	display(taft, 2);	cout << "The wrestler weighed even more.\n";	display(422, 2);	cout << "No stone left unearned\n";	return 0;}void display(const Stonewt & st, int n){	for (int i = 0; i < n; i++)	{		cout << "Wow! ";		st.show_stn();	}}

11.19 stonewt1.h

//stonewt1.h -- revised definition for the Stonewt class#ifndef STONEWT1_H_#define STONEWT1_H_class Stonewt{private:	enum { Lbs_per_stn = 14 };	int stone;	double pds_left;	double pounds;public:	Stonewt(double lbs);	Stonewt(int stn, double lbs);	Stonewt();	~Stonewt();	void show_lbs() const;	void show_stn() const;	operator int() const;	operator double() const;};#endif // !STONEWT1_H_

11.20 stonewt1.cpp

//stonewt1.cpp -- Stonewt class methods + conversion function#include 
   
    #include "stonewt1.h"using namespace std;Stonewt::Stonewt(double lbs){	stone = int(lbs) / Lbs_per_stn;	pds_left = int(lbs) % Lbs_per_stn + lbs - int(lbs);	pounds = lbs;}Stonewt::Stonewt(int stn, double lbs){	stone = stn;	pds_left = lbs;	pounds = stn * Lbs_per_stn + lbs;}Stonewt::Stonewt(){	stone = pounds = pds_left = 0;}Stonewt::~Stonewt(){}void Stonewt::show_stn() const{	cout << stone << " stone, " << pds_left << "pounds\n";}void Stonewt::show_lbs() const{	cout << pounds << " pounds\n";}Stonewt::operator int() const{	return int(pounds + 0.5);}Stonewt::operator double() const{	return pounds;}

11.21 stone1.cpp

//stone1.cpp -- user-defined conversion functions//compile with stonewt1.cpp#include 
   
    #include "stonewt1.h"int main(){	using namespace std;	Stonewt poppins(9, 2.8);	double p_wt = poppins;	cout << "Convert to double => ";	cout << "Poppins: " << p_wt << " pounds.\n";	cout << "Convert to int => ";	cout << "Poppins: " << int(poppins) << " pounds.\n";	return 0;}

课后编程习题

习题1

//vector.h#ifndef VECTOR_H_#define VECTOR_H_#include 
   
    #include 
    
     #include 
     
      #include 
      
       #include 
       
        using namespace std;namespace VECTOR{    class Vector    {    public:        enum Mode { RECT, POL };    private:        double x;        double y;        double mag;        doubleang;        Mode mode;        voidset_mag();        voidset_ang();        voidset_x();        voidset_y();    public:        Vector();        Vector(double n1, double n2, Mode form = RECT);        void reset(double n1, double n2, Mode form = RECT);        ~Vector();        doublexval()const{ return x; }        doubleyval()const{ return y; }        doublemagval()const { return mag; }        doubleangval()const { return ang; }        voidpolar_mode();        voidrect_mode();        Vector operator+(const Vector &b)const;        Vector operator-(const Vector &b)const;        Vector operator-()const;        Vector operator*(double n)const;        friend Vector operator*(double n, const Vector &a);        friend ostream& operator<<(ostream&os, const Vector &v);    };}#endif//vector.cpp#include "vector.h"namespace VECTOR{    const double Rad_to_deg = 45.0 / atan(1.0);    void Vector::set_mag()    {        mag = sqrt(x * x + y * y);    }    void Vector::set_ang()    {        if (x == 0.0 && y == 0.0)        ang = 0.0;        else        ang = atan2(y, x);    }    void Vector::set_x()    {        x = mag * cos(ang);    }    void Vector::set_y()    {        y = mag * sin(ang);    }    Vector::Vector()    {        x = y = mag = ang = 0.0;        mode = RECT;    }    Vector::Vector(double n1, double n2, Mode form)    {        mode = form;        if (form == RECT)        {            x = n1;            y = n2;            set_mag();            set_ang();        }        else if (form == POL)        {            mag = n1;            ang = n2 / Rad_to_deg;            set_x();            set_y();        }        else        {            cout<< "Incorrect 3rd argument to Vector() -- ";            cout<< "vector set to 0\n";            x = y = mag = ang = 0.0;            mode = RECT;        }    }    void Vector::reset(double n1, double n2, Mode form)    {        mode = form;        if (form == RECT)        {            x = n1;            y = n2;            set_mag();            set_ang();        }        else if (form == POL)        {            mag = n1;            ang = n2 / Rad_to_deg;            set_x();            set_y();        }        else        {            cout<< "Incorrect 3rd argument to Vector() -- ";            cout<< "vector set to 0\n";            x = y = mag = ang = 0.0;            mode = RECT;        }    }    Vector::~Vector()    {    }    void Vector::polar_mode()    {        mode = POL;    }    void Vector::rect_mode()    {        mode = RECT;    }    Vector Vector::operator+(const Vector &b)const    {        return Vector(x + b.x, y + b.y);    }    Vector Vector::operator-(const Vector &b)const    {        return Vector(x - b.x, y - b.y);    }    Vector Vector::operator-()const    {        return Vector(-x, -y);    }    Vector Vector::operator*(double n)const    {        return Vector(n*x, n*y);    }    Vector operator*(double n, const Vector &a)    {        return a*n;    }    ostream&operator<<(ostream&os, const Vector &v)    {        if (v.mode == Vector::RECT)            os<< "(x,y) = (" <
        
         << ", " <
         
          << ")"; else if (v.mode == Vector::POL) { os<< "(m,a) = (" <
          
           << ", " <
           
            << ")"; } else os<< "Vector object mode is invalid"; return os; }}//randwalk.cpp#include "vector.h"int main(){ using VECTOR::Vector; srand(time(0)); double direction; Vector step; Vector result(0.0, 0.0); unsigned long steps = 0; double target; double dstep; ofstream fout; fout.open("savesteps.txt"); cout<< "Enter target distance (q to quit): "; while (cin>> target) { fout<< "Enter step length: "; if (!(cin>>dstep)) break; cout<< "Target Distance: " << target << " Step Size: " <
            
             <

习题2

//vector.h#ifndef VECTOR_H_#define VECTOR_H_#include 
   
    #include 
    
     #include 
     
      #include 
      
       using namespace std;namespace VECTOR{	class Vector	{	public:		enum Mode { RECT, POL };	private:		double x;		double y;		Mode mode;		doubleset_mag()const;		doubleset_ang()const;		voidset_x(double mag, double ang);		voidset_y(double mag, double ang);	public:		Vector();		Vector(double n1, double n2, Mode form = RECT);		void reset(double n1, double n2, Mode form = RECT);		~Vector();		doublexval()const { return x; }		doubleyval()const { return y; }		doublemagval()const { return set_mag(); }		doubleangval()const { return set_ang(); }		voidpolar_mode();		voidrect_mode();		Vector operator+(const Vector &b)const;		Vector operator-(const Vector &b)const;		Vector operator-()const;		Vector operator*(double n)const;		friend Vector operator*(double n, const Vector &a);		friend ostream& operator<<(ostream&os, const Vector &v);	};}#endif//vector.cpp#include "vector.h"namespace VECTOR{	const double Rad_to_deg = 45.0 / atan(1.0);	double Vector::set_mag()const	{		return sqrt(x * x + y * y);	}	double Vector::set_ang()const	{		if (x == 0.0 && y == 0.0)			return 0.0;		else			return atan2(y, x);	}	void Vector::set_x(double mag, double ang)	{		x = mag * cos(ang);	}	void Vector::set_y(double mag, double ang)	{		y = mag * sin(ang);	}	Vector::Vector()	{		x = y = 0.0;		mode = RECT;	}	Vector::Vector(double n1, double n2, Mode form)	{		mode = form;		if (form == RECT)		{			x = n1;			y = n2;		}		else if (form == POL)		{			set_x(n1, n2 / Rad_to_deg);			set_y(n1, n2 / Rad_to_deg);		}		else		{			cout << "Incorrect 3rd argument to Vector() -- ";			cout << "vector set to 0\n";			x = y = 0.0;			mode = RECT;		}	}	void Vector::reset(double n1, double n2, Mode form)	{		mode = form;		if (form == RECT)		{			x = n1;			y = n2;		}		else if (form == POL)		{			set_x(n1, n2 / Rad_to_deg);			set_y(n1, n2 / Rad_to_deg);		}		else		{			cout << "Incorrect 3rd argument to Vector() -- ";			cout << "vector set to 0\n";			x = y = 0.0;			mode = RECT;		}	}	Vector::~Vector()	{	}	void Vector::polar_mode()	{		mode = POL;	}	void Vector::rect_mode()	{		mode = RECT;	}	Vector Vector::operator+(const Vector &b)const	{		return Vector(x + b.x, y + b.y);	}	Vector Vector::operator-(const Vector &b)const	{		return Vector(x - b.x, y - b.y);	}	Vector Vector::operator-()const	{		return Vector(-x, -y);	}	Vector Vector::operator*(double n)const	{		return Vector(n*x, n*y);	}	Vector operator*(double n, const Vector &a)	{		return a * n;	}	ostream&operator<<(ostream&os, const Vector &v)	{		if (v.mode == Vector::RECT)			os << "(x,y) = (" << v.x << ", " << v.y << ")";		else if (v.mode == Vector::POL)		{			os << "(m,a) = (" << v.set_mag() << ", "				<< v.set_ang()*Rad_to_deg << ")";		}		else			os << "Vector object mode is invalid";		return os;	}}//randwalk.cpp#include "vector.h"int main(){	using VECTOR::Vector;	srand(time(0));	double direction;	Vector step;	Vector result(0.0, 0.0);	unsigned long steps = 0;	double target;	double dstep;	cout << "Enter target distance (q to quit): ";	while (cin >> target)	{		cout << "Enter step length: ";		if (!(cin >> dstep))			break;		while (result.magval() < target)		{			direction = rand() % 360;			step.reset(dstep, direction, Vector::POL);			result = result + step;			steps++;		}		cout << "After " << steps << " steps, the subject "			"has the following location:\n";		cout << result << endl;		result.polar_mode();		cout << " or\n" << result << endl;		cout << "Average outward distance per step = "			<< result.magval() / steps << endl;		steps = 0;		result.reset(0.0, 0.0);		cout << "Enter target distance (q to quit): ";	}	cout << "Bye!\n";	cin.clear();	while (cin.get() != '\n')		continue;	cin.get();	return 0;}

习题3

3、//vector.h#ifndef VECTOR_H_#define VECTOR_H_#include 
   
    #include 
    
     #include 
     
      #include 
      
       using namespace std;namespace VECTOR{	class Vector	{	public:		enum Mode { RECT, POL };	private:		double x;		double y;		double mag;		double ang;		Mode mode;		voidset_mag();		voidset_ang();		voidset_x();		voidset_y();	public:		Vector();		Vector(double n1, double n2, Mode form = RECT);		void reset(double n1, double n2, Mode form = RECT);		~Vector();		doublexval()const { return x; }		doubleyval()const { return y; }		doublemagval()const { return mag; }		doubleangval()const { return ang; }		voidpolar_mode();		voidrect_mode();		Vector operator+(const Vector &b)const;		Vector operator-(const Vector &b)const;		Vector operator-()const;		Vector operator*(double n)const;		friend Vector operator*(double n, const Vector &a);		friend ostream& operator<<(ostream&os, const Vector &v);	};}#endif//vector.cpp#include "vector.h"namespace VECTOR{	const double Rad_to_deg = 45.0 / atan(1.0);	void Vector::set_mag()	{		mag = sqrt(x * x + y * y);	}	void Vector::set_ang()	{		if (x == 0.0 && y == 0.0)			ang = 0.0;		else			ang = atan2(y, x);	}	void Vector::set_x()	{		x = mag * cos(ang);	}	void Vector::set_y()	{		y = mag * sin(ang);	}	Vector::Vector()	{		x = y = mag = ang = 0.0;		mode = RECT;	}	Vector::Vector(double n1, double n2, Mode form)	{		mode = form;		if (form == RECT)		{			x = n1;			y = n2;			set_mag();			set_ang();		}		else if (form == POL)		{			mag = n1;			ang = n2 / Rad_to_deg;			set_x();			set_y();		}		else		{			cout << "Incorrect 3rd argument to Vector() -- ";			cout << "vector set to 0\n";			x = y = mag = ang = 0.0;			mode = RECT;		}	}	void Vector::reset(double n1, double n2, Mode form)	{		mode = form;		if (form == RECT)		{			x = n1;			y = n2;			set_mag();			set_ang();		}		else if (form == POL)		{			mag = n1;			ang = n2 / Rad_to_deg;			set_x();			set_y();		}		else		{			cout << "Incorrect 3rd argument to Vector() -- ";			cout << "vector set to 0\n";			x = y = mag = ang = 0.0;			mode = RECT;		}	}	Vector::~Vector()	{	}	void Vector::polar_mode()	{		mode = POL;	}	void Vector::rect_mode()	{		mode = RECT;	}	Vector Vector::operator+(const Vector &b)const	{		return Vector(x + b.x, y + b.y);	}	Vector Vector::operator-(const Vector &b)const	{		return Vector(x - b.x, y - b.y);	}	Vector Vector::operator-()const	{		return Vector(-x, -y);	}	Vector Vector::operator*(double n)const	{		return Vector(n*x, n*y);	}	Vector operator*(double n, const Vector &a)	{		return a * n;	}	ostream&operator<<(ostream&os, const Vector &v)	{		if (v.mode == Vector::RECT)			os << "(x,y) = (" << v.x << ", " << v.y << ")";		else if (v.mode == Vector::POL)		{			os << "(m,a) = (" << v.mag << ", "				<< v.ang*Rad_to_deg << ")";		}		else			os << "Vector object mode is invalid";		return os;	}}//randwalk.cpp#include "vector.h"int main(){	using VECTOR::Vector;	srand(time(0));	double direction;	Vector step;	Vector result(0.0, 0.0);	unsigned long steps = 0;	double target;	double dstep;	double numbers, N;	double Min, Max, Sum, Average;	cout << "Enter target distance: ";	cin >> target;	cout << "Enter step length: ";	cin >> dstep;	cout << "Enter test numbers: ";	cin >> numbers;	N = numbers;	Min = Max = Sum = Average = 0.0;	while (numbers)	{		while (result.magval() < target)		{			direction = rand() % 360;			step.reset(dstep, direction, Vector::POL);			result = result + step;			steps++;		}		cout << "After " << steps << " steps once a walk\n";		if (Min == 0 || Max == 0)			Min = Max = steps;		if (Min > steps)			Min = steps;		if (Max < steps)			Max = steps;		Sum += steps;		numbers--;		steps = 0;		result.reset(0.0, 0.0);	}	Average = Sum / N;	cout << "Max steps is " << Max << endl;	cout << "Min steps is " << Min << endl;	cout << "Average steps is " << Average << endl;	cout << "Bye!\n";	cin.clear();	while (cin.get() != '\n')		continue;	cin.get();	return 0;}

习题4

//mytime.h#ifndef MYTIME_H_#define MYTIME_H_#include 
   
    #include 
    
     #include 
     
      using namespace std;class Time{private:	int hours;	int minutes;public:	Time();	Time(int h, int m = 0);	voidAddMin(int m);	voidAddHr(int h);	void Reset(int h = 0, int m = 0);	Time operator*(double n)const;	friend Time operator-(const Time &t1, const Time &t2);	friend Time operator+(const Time &t1, const Time &t2);	friend Time operator*(double m, const Time &t)	{		return t * m;	}	friend ostream& operator<<(ostream&os, const Time &t);};#endif//mytime.cpp#include "mytime.h"Time::Time(){	hours = minutes = 0;}Time::Time(int h, int m){	hours = h;	minutes = m;}void Time::AddMin(int m){	minutes += m;	hours += minutes / 60;	minutes %= 60;}void Time::AddHr(int h){	hours += h;}void Time::Reset(int h, int m){	hours = h;	minutes = m;}Time operator+(const Time &t1, const Time &t2){	Time sum;	sum.minutes = t1.minutes + t2.minutes;	sum.hours = t1.hours + t2.hours + sum.minutes / 60;	sum.minutes %= 60;	return sum;}Time operator-(const Time &t1, const Time &t2){	Time diff;	int tot1, tot2;	tot1 = t1.minutes + 60 * t1.hours;	tot2 = t2.minutes + 60 * t2.hours;	diff.minutes = (tot1 - tot2) % 60;	diff.hours = (tot1 - tot2) / 60;	return diff;}Time Time::operator*(double mult)const{	Time result;	long totalminutes = hours * mult * 60 + minutes * mult;	result.hours = totalminutes / 60;	result.minutes = totalminutes % 60;	return result;}ostream&operator<<(ostream&os, const Time &t){	os << t.hours << " hours, " << t.minutes << " minutes";	return os;}//usetime.cpp#include "mytime.h"int main(){	Time aida(3, 35);	Time tosca(2, 48);	Time temp;	cout << "Aida and Tosca:\n";	cout << aida << "; " << tosca << endl;	temp = aida + tosca;	cout << "Aida + Tosca: " << temp << endl;	temp = aida - tosca;	cout << "Aida - Tosca: " << temp << endl;	temp = aida * 1.17;	cout << "Aida * 1.17: " << temp << endl;	cout << "10.0 * Tosca: " << 10.0 * tosca << endl;	cin.get();	return 0;}

习题5

//stonewt.h#ifndef STONEWT_H_#define STONEWT_H_#include 
   
    #include 
    
     #include 
     
      using namespace std;classStonewt{public:	enum Mode { STN, INPD, FPD };private:	static int constLbs_per_stn = 14;	int stone;	double pds_left;	double pounds;	int pounds_int;	Mode mode;    void set_stn();	void set_pds();	void set_pds_int();public:	Stonewt(double lbs, Mode form);	Stonewt(int stn, double lbs, Mode form);	Stonewt();	~Stonewt();	voidstn_mode();	voidpds_mode();	voidint_pds_mode();	operatorint()const;	operator double()const;	Stonewt operator+(const Stonewt&st)const;	Stonewt operator-(const Stonewt&st)const;	Stonewt operator*(double n)const;	friend Stonewt operator*(double n, const Stonewt&st);	friend ostream&operator<<(ostream&os, const Stonewt&st);};#endif//stonewt.cpp#include "stonewt.h"voidStonewt::set_stn(){	stone = int(pounds) / Lbs_per_stn;	pds_left = int(pounds) % Lbs_per_stn + pounds - int(pounds);}voidStonewt::set_pds(){	pounds = stone * Lbs_per_stn + pds_left;}voidStonewt::set_pds_int(){	pounds_int = int(pounds);}Stonewt::Stonewt(double lbs, Mode form){	mode = form;	if (form == STN)	{		stone = int(lbs) / Lbs_per_stn;		pds_left = int(lbs) % Lbs_per_stn + lbs - int(lbs);		set_pds();		set_pds_int();	}	else if (form == INPD)	{		pounds_int = int(lbs);		pounds = lbs;		set_stn();	}	else if (form == FPD)	{		pounds = lbs;		set_pds_int();		set_stn();	}	else	{		cout << "Incorrect 3rd argument to Stonewt() -- ";		cout << "Stonewt set to 0\n";		stone = pounds = pds_left = 0;		mode = STN;	}}Stonewt::Stonewt(int stn, double lbs, Mode form){	mode = form;	if (form == STN)	{		stone = stn;		pds_left = lbs;		set_pds();		set_pds_int();	}	else if (form == INPD)	{		pounds_int = int(stn*Lbs_per_stn + lbs);		pounds = stn * Lbs_per_stn + lbs;		set_stn();	}	else if (form == FPD)	{		pounds = stn * Lbs_per_stn + lbs;		set_pds_int();		set_stn();	}	else	{		cout << "Incorrect 3rd argument to Stonewt() -- ";		cout << "Stonewt set to 0\n";		stone = pounds = pds_left = 0;		mode = STN;	}}Stonewt::Stonewt(){	stone = pounds = pds_left = 0;	mode = STN;}Stonewt::~Stonewt(){}void Stonewt::stn_mode(){	mode = STN;}void Stonewt::pds_mode(){	mode = FPD;}void Stonewt::int_pds_mode(){	mode = INPD;}Stonewt::operator int()const{	return int(pounds + 0.5);}Stonewt::operator double()const{	return pounds;}Stonewt Stonewt::operator+(const Stonewt&st)const{	return Stonewt(pounds + st.pounds, st.mode);}Stonewt Stonewt::operator-(const Stonewt&st)const{	return Stonewt(pounds - st.pounds, st.mode);}Stonewt Stonewt::operator*(double n)const{	return Stonewt(pounds*n, mode);}Stonewt operator*(double n, const Stonewt&st){	return Stonewt(n*st.pounds, st.mode);}ostream&operator<<(ostream&os, const Stonewt&st){	if (st.mode == Stonewt::STN)		os << st.stone << " stone, " << st.pds_left << " pounds\n";	else if (st.mode == Stonewt::INPD)		os << st.pounds_int << " pounds(int)\n";	else if (st.mode == Stonewt::FPD)		os << st.pounds << " pounds(double)\n";	else		os << "Error in type\n";	return os;}//stone.cpp#include "stonewt.h"int main(){	Stonewt incognito(275, Stonewt::FPD);	Stonewt wolfe(285.7, Stonewt::STN);	Stonewt taft(21, 8, Stonewt::INPD);	Stonewt temp;	cout << "The celebrity weighed ";	cout << incognito << endl;	cout << "The detective weighed ";	cout << wolfe << endl;	cout << "The President weighed ";	cout << taft << endl;	temp = incognito + wolfe;	cout << "Incognito + Wolfe = " << temp << endl;	temp = wolfe - incognito;	cout << "Wolfe - Incognito = " << temp << endl;	temp = taft * 10.0;	cout << "Taft * 10.0 = " << temp << endl;	temp = 10.0 * taft;	cout << "10.0 * Taft = " << temp << endl;	cin.get();	return 0;}

习题6

//stonewt.h#ifndef STONEWT_H_#define STONEWT_H_#include 
   
    #include 
    
     #include 
     
      using namespace std;class Stonewt{private:	enum { Lbs_per_stn = 14 };	int stone;	double pds_left;	double pounds;public:	Stonewt(double lbs);	Stonewt(int stn, double lbs);	Stonewt();	~Stonewt();	bool operator<(const Stonewt&st)const;	bool operator<=(const Stonewt&st)const;	bool operator>(const Stonewt&st)const;	bool operator>=(const Stonewt&st)const;	bool operator==(const Stonewt&st)const;	bool operator!=(const Stonewt&st)const;	friend ostream&operator<<(ostream&os, const Stonewt&st);}；#endif//stonewt.cpp#include "stonewt.h"Stonewt::Stonewt(double lbs){	stone = int(lbs) / Lbs_per_stn;	pds_left = int(lbs) % Lbs_per_stn + lbs - int(lbs);	pounds = lbs;}Stonewt::Stonewt(int stn, double lbs){	stone = stn;	pds_left = lbs;	pounds = stn * Lbs_per_stn + lbs;}Stonewt::Stonewt(){	stone = pounds = pds_left = 0;}Stonewt::~Stonewt(){}bool Stonewt::operator<(const Stonewt&st)const{	if (pounds < st.pounds)		return true;	else		return false;}bool Stonewt::operator<=(const Stonewt&st)const{	if (pounds <= st.pounds)		return true;	else		return false;}bool Stonewt::operator>(const Stonewt&st)const{	if (pounds > st.pounds)		return true;	else		return false;}bool Stonewt::operator>=(const Stonewt&st)const{	if (pounds >= st.pounds)		return true;	else		return false;}bool Stonewt::operator==(const Stonewt&st)const{	if (pounds == st.pounds)		return true;	else		return false;}bool Stonewt::operator!=(const Stonewt&st)const{	if (pounds != st.pounds)		return true;	else		return false;}ostream&operator<<(ostream&os, const Stonewt&st){	os << st.pounds << " pounds\n";	return os;}//stone.cpp#include "stonewt.h"int main(){	Stonewt sw[6] = { 10.0, 11.0, 12.5 };	Stonewt temp(11.0);	for (int i = 3; i < 6; i++)	{		double input;		cout << "Enter #" << i + 1 << ": ";		cin >> input;		sw[i] = input;	}	for (inti = 0; i < 6; i++)		cout << "#" << i << ": " << sw[i];	int count = 0;	Stonewt Min = sw[0];	Stonewt Max = sw[0];	for (int i = 0; i < 6; i++)	{		if (Min > sw[i])			Min = sw[i];		if (Max < sw[i])			Max = sw[i];		if (temp >= sw[i])			count++;	}	cout << "The Min pounds: " << Min;	cout << "The Max pounds: " << Max;	cout << "The numbers not under 11 pounds: " << count;	cin.get();	cin.get();	return 0;}

习题7

//complexh.h#ifndef COMPLEX_H_#define COMPLEX_H_#include 
   
    #include 
    
     #include 
     
      #include 
      
       using namespace std;class Complex{private:	double real;	double imaginary;public:	Complex();	Complex(double n1);	Complex(double n1, double n2);	~Complex();	Complex operator+(const Complex &c)const;	Complex operator-(const Complex &c)const;	Complex operator*(const Complex &c)const;	Complex operator*(double n)const;	Complex operator~()const;	friend Complex operator*(double n, const Complex &c);	friend ostream&operator<<(ostream&os, const Complex &c);	friend istream&operator>>(istream&is, Complex &c);};#endif//complex.cpp#include "complexh.h"Complex::Complex(){	real = 0.0;	imaginary = 0.0;}Complex::Complex(double n1){	real = n1;	imaginary = 0.0;}Complex::Complex(double n1, double n2){	real = n1;	imaginary = n2;}Complex::~Complex(){}Complex Complex::operator+(const Complex &c)const{	return Complex(real + c.real, imaginary + c.imaginary);}Complex Complex::operator-(const Complex &c)const{	return Complex(real - c.real, imaginary - c.imaginary);}Complex Complex::operator*(const Complex &c)const{	double real_s;	double imaginary_s;	real_s = real * c.real - imaginary * c.imaginary;	imaginary_s = real * c.imaginary + imaginary * c.real;	return Complex(real_s, imaginary_s);}Complex Complex::operator*(double n)const{	return Complex(n*real, n*imaginary);}Complex Complex::operator~()const{	return Complex(real, -imaginary);}Complex operator*(double n, const Complex &c){	return Complex(n*c.real, n*c.imaginary);}ostream &operator<<(ostream&os, const Complex &c){	os << "(" << c.real << ", " << c.imaginary << "i)";	return os;}istream &operator>>(istream&is, Complex &c){	cout << "Real: ";	if (is >> c.real)	{		cout << "Imaginary: ";		is >> c.imaginary;	}	return is;}//useComplex.cpp#include "complexh.h"int main(){	Complex a(3.0, 4.0);	Complex c;	char ch;	cout << "Enter a complex number (q to quit): ";	while (cin >> ch)	{		if (ch == 'q' || ch == 'Q')			break;		else		{			cin >> c;			cout << "c is " << c << '\n';			cout << "Complex conjugate is " << ~c << '\n';			cout << "a is " << a << '\n';			cout << "a + c is " << a + c << '\n';			cout << "a - c is " << a - c << '\n';			cout << "a * c is " << a * c << '\n';			cout << "2 * c is " << 2 * c << '\n';		}		cout << "Enter a complex number (q to quit): ";	}	cout << "Done!\n";	cin.get();	cin.get();	return 0;}

 

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