C++ Primer Plus (第6版) 中文版 第十一章 使用类 编程练习答案
第十一章 编程练习
1.修改程序清单11.15, 使之将一系列连续的随机漫步者位置写入文件中。对于每个位置,用步号进行标示。另外,让该程序将初始条件(目标距离和步长)以结果小结写入到该文件中。
头文件:
// vect.h -- Vector class with <<, mode state
#ifndef VECTOR_H_
#define VECTOR_H_
#include <iostream>
namespace VECTOR
{
class Vector
{
public:
enum Mode {RECT, POL};
// RECT for rectangular, POL for Polar modes
private:
double x; // horizontal value
double y; // vertical value
double mag; // length of vector
double ang; // direction of vector in degrees
Mode mode; // RECT or POL
// private methods for setting values
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;} // report x value
double yval() const {return y;} // report y value
double magval() const {return mag;} // report magnitude
double angval() const {return ang;} // report angle
void polar_mode(); // set mode to POL
void rect_mode(); // set mode to RECT
// operator overloading
Vector operator+(const Vector & b) const;
Vector operator-(const Vector & b) const;
Vector operator-() const;
Vector operator*(double n) const;
// friends
friend Vector operator*(double n, const Vector & a);
friend std::ostream & operator<<(std::ostream & os, const Vector & v);
};
} // end namespace VECTOR
#endif
类中成员函数使用方法解释文件:
// vect.cpp -- methods for the Vector class
#include <cmath>
#include "vector.h" // includes <iostream>
using std::sqrt;
using std::sin;
using std::cos;
using std::atan;
using std::atan2;
using std::cout;
namespace VECTOR
{
// compute degrees in one radian
const double Rad_to_deg = 45.0 / atan(1.0);
// should be about 57.2957795130823
// private methods
// calculates magnitude from x and y
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);
}
// set x from polar coordinate
void Vector::set_x()
{
x = mag * cos(ang);
}
// set y from polar coordinate
void Vector::set_y()
{
y = mag * sin(ang);
}
// public methods
Vector::Vector() // default constructor
{
x = y = mag = ang = 0.0;
mode = RECT;
}
// construct vector from rectangular coordinates if form is r
// (the default) or else from polar coordinates if form is p
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;
}
}
// reset vector from rectangular coordinates if form is
// RECT (the default) or else from polar coordinates if
// form is POL
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() // destructor
{
}
void Vector::polar_mode() // set to polar mode
{
mode = POL;
}
void Vector::rect_mode() // set to rectangular mode
{
mode = RECT;
}
// operator overloading
// add two Vectors
Vector Vector::operator+(const Vector & b) const
{
return Vector(x + b.x, y + b.y);
}
// subtract Vector b from a
Vector Vector::operator-(const Vector & b) const
{
return Vector(x - b.x, y - b.y);
}
// reverse sign of Vector
Vector Vector::operator-() const
{
return Vector(-x, -y);
}
// multiply vector by n
Vector Vector::operator*(double n) const
{
return Vector(n * x, n * y);
}
// friend methods
// multiply n by Vector a
Vector operator*(double n, const Vector & a)
{
return a * n;
}
// display rectangular coordinates if mode is RECT,
// else display polar coordinates if mode is POL
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;
}
} // end namespace VECTOR
对编程练习11.15的修改:
// randwalk.cpp -- using the Vector class
// compile with the vect.cpp file
#include <iostream>
#include<fstream>
#include <cstdlib> // rand(), srand() prototypes
#include <ctime> // time() prototype
#include "vector.h"
int main()
{
using namespace std;
using VECTOR::Vector;
ofstream fout;
fout.open("thewalk.txt");
srand(time(0)); // seed random-number generator
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;
fout<<"Target Distance: "<<target<<" , "<<"Step Size: "<<dstep<<endl;
while (result.magval() < target)
{
direction = rand() % 360;
step.reset(dstep, direction, Vector::POL);
result = result + step;
fout<<steps<<" : "<<result<<endl;
steps++;
}
fout << "After " << steps << " steps, the subject "
"has the following location:\n";
fout << result << endl;
cout << "After " << steps << " steps, the subject "
"has the following location:\n";
cout << result << endl;
result.polar_mode();
fout << " or\n" << result << endl;
fout << "Average outward distance per step = "
<< result.magval()/steps << endl;
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";
/* keep window open
cin.clear();
while (cin.get() != '\n')
continue;
cin.get();
*/
return 0;
}
程序运行结果:
2.对Vector类的头文件(程序清单11.13) 和实现文件(程序清单11.14 进行修改),使其不再存储矢量的长度和角度,而是在magval()和angval()被调用时计算它们应保留公有接口不变(公有方法及参数不变),但对私有部分(包括一些私有方法)和方法实现进行修改。然后,使用程序清单11.15 对修改后的版本进行测试,结果应该与以前相同,因为Vector类的公有接口与原来相同。
头文件: vect.h
// vect.h -- Vector class with <<, mode state
#ifndef VECTOR_H_
#define VECTOR_H_
#include <iostream>
namespace VECTOR
{
class Vector
{
public:
enum Mode {RECT, POL};
// RECT for rectangular, POL for Polar modes
private:
double x; // horizontal value
double y; // vertical value
Mode mode;
void set_x(double mag,double ang);
void set_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();
double xval() const {return x;} // report x value
double yval() const {return y;} // report y value
double magval() const ; // report magnitude
double angval() const; // report angle
void polar_mode(); // set mode to POL
void rect_mode(); // set mode to RECT
// operator overloading
Vector operator+(const Vector & b) const;
Vector operator-(const Vector & b) const;
Vector operator-() const;
Vector operator*(double n) const;
// friends
friend Vector operator*(double n, const Vector & a);
friend std::ostream & operator<<(std::ostream & os, const Vector & v);
};
} // end namespace VECTOR
#endif
头文件中的函数成员解释文件: vect.cpp
// vect.cpp -- methods for the Vector class
#include <cmath>
#include "alter_vector.h" // includes <iostream>
using std::sqrt;
using std::sin;
using std::cos;
using std::atan;
using std::atan2;
using std::cout;
namespace VECTOR
{
// compute degrees in one radian
const double Rad_to_deg = 45.0 / atan(1.0);
// should be about 57.2957795130823
// private methods
// set x from polar coordinate
double Vector::magval()const
{
return sqrt(x * x + y * y);
}
double Vector::angval()const
{
if (x ==0.0 & y ==0)
return 0.0;
else
return atan2(y,x);
}
void Vector::set_x(double mag,double ang)
{
x = mag * cos(ang);
}
// set y from polar coordinate
void Vector::set_y(double mag,double ang)
{
y = mag * sin(ang);
}
// public methods
Vector::Vector() // default constructor
{
x = y = 0.0;
mode = RECT;
}
// construct vector from rectangular coordinates if form is r
// (the default) or else from polar coordinates if form is p
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;
}
}
// reset vector from rectangular coordinates if form is
// RECT (the default) or else from polar coordinates if
// form is POL
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() // destructor
{
}
void Vector::polar_mode() // set to polar mode
{
mode = POL;
}
void Vector::rect_mode() // set to rectangular mode
{
mode = RECT;
}
// operator overloading
// add two Vectors
Vector Vector::operator+(const Vector & b) const
{
return Vector(x + b.x, y + b.y);
}
// subtract Vector b from a
Vector Vector::operator-(const Vector & b) const
{
return Vector(x - b.x, y - b.y);
}
// reverse sign of Vector
Vector Vector::operator-() const
{
return Vector(-x, -y);
}
// multiply vector by n
Vector Vector::operator*(double n) const
{
return Vector(n * x, n * y);
}
// friend methods
// multiply n by Vector a
Vector operator*(double n, const Vector & a)
{
return a * n;
}
// display rectangular coordinates if mode is RECT,
// else display polar coordinates if mode is POL
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.magval() << ", "
<< v.angval() * Rad_to_deg << ")";
}
else
os << "Vector object mode is invalid";
return os;
}
} // end namespace VECTOR
测试文件:
// randwalk.cpp -- using the Vector class
// compile with the vect.cpp file
#include <iostream>
#include<fstream>
#include <cstdlib> // rand(), srand() prototypes
#include <ctime> // time() prototype
#include "alter_vector.h"
int main()
{
using namespace std;
using VECTOR::Vector;
srand(time(0)); // seed random-number generator
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)
{
ofstream fout;
fout.open("thewalk.txt");
fout << "Enter step length: ";
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++;
}
fout << "After " << steps << " steps, the subject "
"has the following location:\n";
fout << result << endl;
cout << "After " << steps << " steps, the subject "
"has the following location:\n";
cout << result << endl;
result.polar_mode();
fout << " or\n" << result << endl;
fout << "Average outward distance per step = "
<< result.magval()/steps << endl;
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";
/* keep window open
cin.clear();
while (cin.get() != '\n')
continue;
cin.get();
*/
return 0;
}
运行结果:
3.修改程序清单11.15 ,使之报告N次测试中最高、最低和平均步数(其中N是用户输入的整数),而不是报告每次的结果。
// randwalk.cpp -- using the Vector class
// compile with the vect.cpp file
#include <iostream>
#include <cstdlib> // rand(), srand() prototypes
#include <ctime> // time() prototype
#include "alter_vector.h"
int main()
{
using namespace std;
using VECTOR::Vector;
srand(time(0)); // seed random-number generator
double direction;
Vector step;
Vector result(0.0, 0.0);
unsigned long steps = 0;
double target;
double dstep;
unsigned long maxstep;
unsigned long minstep;
unsigned long sumsteps = 0;
double averagestep;
int i=0;
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";
if (i==0)
{
maxstep = steps;
minstep = steps;
}
++i;
if(maxstep<steps)
maxstep=steps;
if (minstep>steps)
minstep=steps;
sumsteps +=steps;
averagestep=sumsteps/i;
cout<<"The maxstep is "<<maxstep<<endl;
cout<<"The minstep is "<<minstep<<endl;
cout<<"The averagestep is "<<averagestep<<endl;
steps = 0;
result.reset(0.0, 0.0);
cout << "Enter target distance (q to quit): ";
}
cout << "Bye!\n";
return 0;
}
运行结果:
4.重新编写最后的Time类示例(程序清单11.10、 程序清单11.11 和程序清单11.12), 使友元函数来实现所有的重载运算符。
程序清单11.10修改:
// mytime.h -- Time class with friends
#ifndef MYTIME3_H_
#define MYTIME3_H_
#include <iostream>
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);
friend Time operator+(const Time & m, const Time & t);
friend Time operator-(const Time & m, const Time & t);
friend Time operator*(const Time & m, double n);
friend Time operator*(double m, const Time & t)
{ return t * m; } // inline definition
friend std::ostream & operator<<(std::ostream & os, const Time & t);
};
#endif
程序清单11.11修改:
// mytime.cpp -- implementing Time methods
#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 & m, const Time & t)
{
Time sum;
sum.minutes=m.minutes+t.minutes;
sum.hours=m.hours+t.hours+sum.minutes/60;
sum.minutes %=60;
return sum;
}
Time operator-(const Time & m, const Time & t)
{
Time diff;
int tot1, tot2;
tot1 = t.minutes+ 60*t.hours;
tot2 = m.minutes+60*m.hours;
diff.minutes=(tot2-tot1)%60;
diff.hours=(tot2-tot1)/60;
return diff;
}
Time operator*(const Time & m, double n)
{
Time result;
long totalminutes = m.hours * n * 60 +m.minutes * n;
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;
}
程序清单11.12修改:
//usetime.cpp -- using the fourth draft of the Time class
// compile usetime.cpp and mytime.cpp together
#include <iostream>
#include "mytime.h"
int main()
{
using std::cout;
using std::endl;
Time aida(3, 35);
Time tosca(2, 48);
Time temp;
cout << "Aida and Tosca:\n";
cout << aida<<"; " << tosca << endl;
temp = aida + tosca; // operator+()
cout << "Aida + Tosca: " << temp << endl;
temp = aida* 1.17; // member operator*()
cout << "Aida * 1.17: " << temp << endl;
cout << "10.0 * Tosca: " << 10.0 * tosca << endl;
std::cin.get();
return 0;
}
运行结果:
5.重新编写Stonewt类(程序清单11.16 和程序清单11.17 ),使它有一个状态成员,由该成员控制对象应转换为英石格式、整数磅格式(翻译的不合适,应该是磅数格式)还是浮点磅格式(多少stone, 多少pounds)。重载<<运算符,使它来替换show_stn()和show_lbs()方法。 重载加法、减法和乘法运算符,以便可以对Stonewt进行加、减、乘运算。编写一个使用所有类方法和友元的小程序,来测试这个类。
程序清单11.16修改:
// stonewt.h -- definition for the Stonewt class
#ifndef STONEWT_H_
#define STONEWT_H_
class Stonewt
{
private:
enum Mode{STONE,POUND,FLOAT};
Mode model;
enum {Lbs_per_stn = 14}; // pounds per stone
//浮点格式
int stone; // whole stones
double pds_left; // fractional pounds
//整数磅
double pounds; // entire weight in pounds
public:
Stonewt(double lbs); // constructor for double pounds
Stonewt(int stn, double lbs); // constructor for stone, lbs
Stonewt(); // default constructor
~Stonewt();
//重载加法、减法和乘法运算符
Stonewt operator+(const Stonewt & s) const;
Stonewt operator-(const Stonewt & s) const;
Stonewt operator*(double n) const;
void set_model_STONE();
void set_model_POUND();
void set_model_FLOAT();
friend Stonewt operator*(double n ,const Stonewt & s)
{
return s * n;
}
friend std::ostream&
operator<<(std::ostream & os,const Stonewt & s);
};
#endif
程序清单11.17修改:
// stonewt.cpp -- Stonewt methods
#include <iostream>
using std::cout;
#include "Stonewt.h"
// construct Stonewt object from double value
Stonewt::Stonewt(double lbs)
{
stone = int (lbs) / Lbs_per_stn; // integer division
pds_left = int (lbs) % Lbs_per_stn + lbs - int(lbs);
pounds = lbs;
model = POUND;
}
// construct Stonewt object from stone, double values
Stonewt::Stonewt(int stn, double lbs)
{
stone = stn;
pds_left = lbs;
pounds = stn * Lbs_per_stn +lbs;
model = FLOAT;
}
Stonewt::Stonewt() // default constructor, wt = 0
{
stone = pounds = pds_left = 0;
model = STONE;
}
Stonewt::~Stonewt() // destructor
{
}
void Stonewt::set_model_STONE()
{
model = STONE;
}
void Stonewt::set_model_POUND()
{
model = POUND;
}
void Stonewt::set_model_FLOAT()
{
model = FLOAT;
}
Stonewt Stonewt::operator+(const Stonewt & s) const
{
Stonewt temp;
temp.pounds=pounds+s.pounds;
temp.stone = temp.pounds / Lbs_per_stn;
temp.pds_left=int(temp.pounds)%Lbs_per_stn + temp.pounds - int(temp.pounds);
return temp;
}
Stonewt Stonewt::operator-(const Stonewt & s) const
{
Stonewt temp;
temp.pounds=pounds-s.pounds;
temp.stone = temp.pounds / Lbs_per_stn;
temp.pds_left=int(temp.pounds)%Lbs_per_stn + temp.pounds - int(temp.pounds);
return temp;
}
Stonewt Stonewt::operator*(double n) const
{
Stonewt temp;
temp.pounds=pounds*n;
temp.stone = temp.pounds / Lbs_per_stn;
temp.pds_left=int(temp.pounds)%Lbs_per_stn + temp.pounds - int(temp.pounds);
return temp;
}
std::ostream & operator<<(std::ostream & os,const Stonewt & s)
{
if (s.model==Stonewt::STONE)
{
double stone = s.stone + s.pds_left / Stonewt::Lbs_per_stn;
os<<stone<<" stones\n";
}
else if (s.model==Stonewt::POUND)
os<<s.pounds<<" pounds\n";
else
os<<s.stone<<" stones, "<<s.pds_left<<" pounds\n";
return os;
}
程序清单11.18修改:
// stone.cpp -- user-defined conversions
// compile with stonewt.cpp
#include <iostream>
using std::cout;
#include "stonewt.h"
void display(const Stonewt & st, int n);
int main()
{
Stonewt incognito = 275; // uses constructor to initialize
Stonewt wolfe(285.7); // same as Stonewt wolfe = 285.7;
Stonewt taft(21, 8);
cout << "The incognito = 275 weighed ";
incognito.set_model_POUND();
cout<<incognito;
incognito.set_model_STONE();
cout<<incognito;
incognito.set_model_FLOAT();
cout<<incognito;
cout << "The wolfe(285.7) weighed ";
wolfe.set_model_POUND();
cout<<wolfe;
wolfe.set_model_STONE();
cout<<wolfe;
wolfe.set_model_FLOAT();
cout<<wolfe;
cout << "The taft(21, 8) weighed ";
taft.set_model_POUND();
cout<<taft;
taft.set_model_STONE();
cout<<taft;
taft.set_model_FLOAT();
cout<<taft;
Stonewt sum=wolfe+taft;
Stonewt diff=wolfe-taft;
Stonewt product1=taft*2;
Stonewt product2=2*taft;
cout<<"SUM : "<<sum<<std::endl;
cout<<"DIFF : "<<diff<<std::endl;
cout<<"PRODUCT1 : "<<product1<<std::endl;
cout<<"PRODUCT2 : "<<product2<<std::endl;
std::cin.get();
return 0;
}
运行结果:
6.重新编写Stonewt类(程序清单11.16 和程序清单11.17 ),重载全部6个关系运算符。
运算符对pounds成员进行比较,并返回一个bool值。编写一个程序,它声明一个包含6个Stonewt对象的数组,并在数组声明中初始化前3个对象。然后使用循环来读取用于设置剩余3个数组元素的值。接着报告最小的元素、最大的元素以及大于等于11英石的元素的数量(最简单的方法是创建一个Stonewt对象,并将其初始化为11英石,然后将其同其他对象进行比较)。
程序清单11.16修改:
// stonewt.h -- definition for the Stonewt class
#ifndef STONEWT_H_
#define STONEWT_H_
class Stonewt
{
private:
enum {Lbs_per_stn = 14}; // pounds per stone
int stone; // whole stones
double pds_left; // fractional pounds
double pounds; // entire weight in pounds
public:
Stonewt(double lbs); // constructor for double pounds
Stonewt(int stn, double lbs); // constructor for stone, lbs
Stonewt(); // default constructor
~Stonewt();
bool operator<(const Stonewt & s);
bool operator<=(const Stonewt & s);
bool operator>(const Stonewt & s);
bool operator>=(const Stonewt & s);
bool operator==(const Stonewt & s);
bool operator!=(const Stonewt & s);
void show_lbs() const; // show weight in pounds format
void show_stn() const; // show weight in stone format
};
#endif
程序清单11.17修改:
// stonewt.cpp -- Stonewt methods
#include <iostream>
using std::cout;
#include "alter_Stonewt.h"
// construct Stonewt object from double value
Stonewt::Stonewt(double lbs)
{
stone = int (lbs) / Lbs_per_stn; // integer division
pds_left = int (lbs) % Lbs_per_stn + lbs - int(lbs);
pounds = lbs;
}
// construct Stonewt object from stone, double values
Stonewt::Stonewt(int stn, double lbs)
{
stone = stn;
pds_left = lbs;
pounds = stn * Lbs_per_stn +lbs;
}
Stonewt::Stonewt() // default constructor, wt = 0
{
stone = pounds = pds_left = 0;
}
Stonewt::~Stonewt() // destructor
{
}
bool Stonewt:: operator<(const Stonewt & s)
{
if(pounds<s.pounds)
return true;
else
return false;
}
bool Stonewt:: operator<=(const Stonewt & s)
{
if(pounds<=s.pounds)
return true;
else
return false;
}
bool Stonewt:: operator>(const Stonewt & s)
{
if(pounds>s.pounds)
return true;
else
return false;
}
bool Stonewt:: operator>=(const Stonewt & s)
{
if(pounds>=s.pounds)
return true;
else
return false;
}
bool Stonewt:: operator==(const Stonewt & s)
{
if(pounds==s.pounds)
return true;
else
return false;
}
bool Stonewt:: operator!=(const Stonewt & s)
{
if(pounds!=s.pounds)
return true;
else
return false;
}
// show weight in stones
void Stonewt::show_stn() const
{
cout << stone << " stone, " << pds_left << " pounds\n";
}
// show weight in pounds
void Stonewt::show_lbs() const
{
cout << pounds << " pounds\n";
}
程序清单11.18
// stone.cpp -- user-defined conversions
// compile with stonewt.cpp
#include <iostream>
using namespace std;
#include "alter_Stonewt.h"
int main()
{
Stonewt array[6] = {275,Stonewt(285.7),Stonewt(21,8)};
double input;
Stonewt comparison_value = Stonewt(11,0);
Stonewt max=array[0];
Stonewt min=array[0];
int sum=0;
for (int i=3;i<6;i++)
{
cout<<"Enter the "<<i+1<<" pounds: ";
cin>>input;
array[i]=Stonewt(input);
cin.get();
}
for (int i=1;i<6;i++)
{
if (max<array[i])
max=array[i];
if (min>array[i])
min=array[i];
if(array[i]>=comparison_value)
sum++;
}
cout<<"MAX:\n";
max.show_lbs();
max.show_stn();
cout<<"\nMIN:\n";
min.show_lbs();
min.show_stn();
cout<<endl<<"There are "<<sum<<" exceed 11 stone.\n";
cin.get();
return 0;
}
运行结果:
7.操作复数的算术运算。
头文件://–complex.h —A class that defines basic functions of plurals
//--complex.h ---A class that defines basic functions of plurals
#ifndef COMPLEX_H_
#define COMPLEX_H_
class complex0
{
private:
double realpart;
double imagpart;
public:
complex0(double realnumber=0,double imagnumber=0);
~complex0();
friend complex0 operator+(const complex0 & m,const complex0 & s);
friend complex0 operator-(const complex0 & m,const complex0 & s);
friend complex0 operator*(const complex0 & m,const complex0 & s);
friend complex0 operator*(double x,const complex0 & s);
friend complex0 operator~(const complex0 & s);
friend std::istream & operator>>(std::istream & is, complex0 & s);
friend std::ostream & operator<<(std::ostream & os ,const complex0 & s);
};
#endif
方法文件://complex.cpp—method definitions for member functions
//complex.cpp---method definitions for member functions
#include<iostream>
#include"complex0.h"
using namespace std;
complex0::complex0(double realnumber,double imagnumber)
{
realpart=realnumber;
imagpart=imagnumber;
}
complex0::~complex0()
{
cout<<"this is a destructor...\n";
}
complex0 operator+(const complex0 & m,const complex0 & s)
{
complex0 temp;
temp.realpart=m.realpart+s.realpart;
temp.imagpart=m.imagpart+s.imagpart;
return temp;
}
complex0 operator-(const complex0 & m,const complex0 & s)
{
complex0 temp;
temp.realpart=m.realpart-s.realpart;
temp.imagpart=m.imagpart-s.imagpart;
return temp;
}
complex0 operator*(const complex0 & m,const complex0 & s)
{
complex0 temp;
temp.realpart=m.realpart*s.realpart-m.imagpart*s.imagpart;
temp.imagpart=m.realpart*s.imagpart+m.imagpart*s.realpart;
return temp;
}
complex0 operator*(double x,const complex0 & s)
{
complex0 temp;
temp.realpart=x*s.realpart;
temp.imagpart=x*s.imagpart;
return temp;
}
complex0 operator~(const complex0 & s)
{
complex0 temp;
temp.realpart=s.realpart;
temp.imagpart=-1*s.imagpart;
return temp;
}
std::istream & operator>>(std::istream & is, complex0 & s)
{
std::cout<<"realpart: ";
is>>s.realpart;
if(!is)
return is;
std::cout<<"imagpart: ";
is>>s.imagpart;
return is;
}
std::ostream & operator<<(std::ostream & os ,const complex0 & s)
{
os<<"("<<s.realpart<<" , "<<s.imagpart<<"i)";
return os;
}
测试文件://usecomplex.cpp–exercises using plural classes
//usecomplex.cpp--exercises using plural classes
#include<iostream>
using namespace std;
#include"complex0.h"
int main()
{
complex0 a(3.0,4.0);
complex0 c;
cout<<"Enter a complex number (q to quit):\n";
while (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):\n";
}
cout<<"Done!\n";
cin.get();
system("pause");
return 0;
}
运行结果:
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