C++ primer Plus（第六版）中文版 第十一章 使用类 编程练习答案
2019-01-15 19:58
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第十一章 使用类
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。该文件的内容与下面类似：
Target Distance: 100, Step Size: 20
0: (x,y) = (0, 0)
1: (x,y) = (-11.4715, 16.383)
2: (x,y) = (-8.68807, -3.42232)
...
26: (x,y) = (42.2919, -78.2594)
27: (x,y) = (58.6749, -89.7309)
After 27 steps, the subject has the following location:
(x,y) = (58.6749, -89.7309)
or
(m,a) = (107.212, -56.8194)
Average outward distance per step = 3.97081
书中随机漫步程序如下：
[code]// 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
[code]// vect.cpp -- methods for the Vector class
#include <cmath>
#include "vect.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
[code]// randwalk.cpp -- using the Vector class （程序清单11.5）
// compile with the vect.cpp file
#include <iostream>
#include <cstdlib> // rand(), srand() prototypes
#include <ctime> // time() prototype
#include "vect.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)
{
cout << "Enter step length: ";
if (!(cin >> dstep))
break;
while (result.magval() < target)
{
direction = rand() % 360;
step.reset(dstep, direction, 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";
/* keep window open
cin.clear();
while (cin.get() != '\n')
continue;
cin.get();
*/
return 0;
}
//程序清单11.5修改后如下：
[code]// randwalk.cpp -- using the Vector class
// compile with the vect.cpp file
#include <iostream>
#include <cstdlib> // rand(), srand() prototypes
#include <ctime> // time() prototype
#include <fstream> //修改时添加
#include "vect.h"
int main()
{
using namespace std;
using VECTOR::Vector;
ofstream fout; //修改时添加
fout.open("thewalk.txt"); //修改时添加
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;
//修改时添加
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 << ": (x,y) = " << result << endl; //修改时添加
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;
//修改时添加
fout << "After " << steps << " steps, the subject "
"has the following location:\n";
result.rect_mode();
fout << result << endl;
result.polar_mode();
fout << " or\n" << result << endl;
fout << "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";
return 0;
}
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。
修改后：
[code]程序清单11.13 如下：
// 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; // RECT or POL
// private methods for setting values
void set_x(double mag, double ang); //通过用户输入的mag和ang求x
void set_y(double mag, double ang); //通过用户输入的mag和ang求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; // report magnitude //有修改，直接返回计算值
double angval() const; // report angle //有修改，直接返回计算值
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
[code]程序清单11.14 如下：
// vect.cpp -- methods for the Vector class
#include <cmath>
#include "vect.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
double Vector::magval() const
{
return sqrt(x * x + y * y);
}
double Vector::angval() const
{
if (x == 0.0 && y == 0.0)
return 0.0;
else
return atan2(y, x);
}
// set x from polar coordinate
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
[code]//程序清单11.5（未修改） 如下：
// randwalk.cpp -- using the Vector class
// compile with the vect.cpp file
#include <iostream>
#include <cstdlib> // rand(), srand() prototypes
#include <ctime> // time() prototype
#include "vect.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)
{
cout << "Enter step length: ";
if (!(cin >> dstep))
break;
while (result.magval() < target)
{
direction = rand() % 360;
step.reset(dstep, direction, 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";
/* keep window open
cin.clear();
while (cin.get() != '\n')
continue;
cin.get();
*/
return 0;
}
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
修改后
[code]//程序清单11.5 如下：
// randwalk.cpp -- using the Vector class
// compile with the vect.cpp file
#include <iostream>
#include <cstdlib> // rand(), srand() prototypes
#include <ctime> // time() prototype
#include "vect.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 sumstep = 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;
sumstep += steps;
averagestep = sumstep/i;
cout << "Now, maxstep is " << maxstep << endl;
cout << "Now, minstep is " << minstep << endl;
cout << "Now, averagestep is " << averagestep << endl;
// 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";
return 0;
}
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、 程序清单11.11 和程序清单11.12原程序：
[code]// mytime3.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);
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; } // inline definition
friend std::ostream & operator<<(std::ostream & os, const Time & t);
};
#endif
[code]// mytime3.cpp -- implementing Time methods
#include "mytime3.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 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;
}
[code]//usetime3.cpp -- using the fourth draft of the Time class
// compile usetime3.cpp and mytime3.cpp together
#include <iostream>
#include "mytime3.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;
}
修改后：
[code]// mytime3.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 & s, const Time & t);
friend Time operator-(const Time & s, const Time & t);
friend Time operator*(const Time & s, 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
[code]// mytime3.cpp -- implementing Time methods
#include "mytime3.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 & s, const Time & t)
{
Time sum;
sum.minutes = s.minutes + t.minutes;
sum.hours = s.hours + t.hours + sum.minutes / 60;
sum.minutes %= 60;
return sum;
}
Time operator-(const Time & s, const Time & t)
{
Time diff;
int tot1, tot2;
tot1 = t.minutes + 60 * t.hours;
tot2 = s.minutes + 60 * s.hours;
diff.minutes = (tot2 - tot1) % 60;
diff.hours = (tot2 - tot1) / 60;
return diff;
}
Time operator*(const Time & s, double mult)
{
Time result;
long totalminutes = s.hours * mult * 60 + s.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;
}
[code]//usetime3.cpp -- using the fourth draft of the Time class
// compile usetime3.cpp and mytime3.cpp together
#include <iostream>
#include "mytime3.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;
}
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 和程序清单11.17原程序：
[code]// 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();
void show_lbs() const; // show weight in pounds format
void show_stn() const; // show weight in stone format
};
#endif
[code]// 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;
}
// 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
{
}
// 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";
}
修改后：
[code]// stonewt.h -- definition for the Stonewt class
#ifndef STONEWT_H_
#define STONEWT_H_
class Stonewt
{
private:
enum Mode{STO, POU, FLO};
Mode model;
enum {Lbs_per_stn = 14}; // pounds per stone
//浮点磅格式(多少stone, 多少pounds)
int stone; // whole stones
double pds_left; // fractional pounds
//整数磅格式(多少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();
Stonewt operator+(const Stonewt & s) const;
Stonewt operator-(const Stonewt & s) const;
Stonewt operator*(double n) const;
void set_model_STO();
void set_model_POU();
void set_model_FLO();
friend Stonewt operator*(double n, const Stonewt & s) {return s * n;}
friend std::ostream & operator<<(std::ostream & os, const Stonewt & s);
};
#endif
[code]// stonewt.cpp -- Stonewt methods
#include <iostream>
#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 = POU;
}
// 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 = FLO;
}
Stonewt::Stonewt() // default constructor, wt = 0
{
stone = pounds = pds_left = 0;
model = STO;
}
Stonewt::~Stonewt() // destructor
{
}
void Stonewt::set_model_STO()
{
model = STO;
}
void Stonewt::set_model_POU()
{
model = POU;
}
void Stonewt::set_model_FLO()
{
model = FLO;
}
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::STO)
{
double st = s.stone + s.pds_left / Stonewt::Lbs_per_stn;
os << st << " stone\n";
}
if (s.model == Stonewt::POU)
os << s.pounds << " pounds\n";
if (s.model == Stonewt::FLO)
os << s.stone << " stone, " << s.pds_left << " pounds\n";
return os;
}
[code]//usestonewt.cpp
#include <iostream>
#include "stonewt.h"
using namespace std;
int main()
{
Stonewt one; //使用默认构造函数
Stonewt two(187.23); //使用接受一个double值的构造函数
Stonewt three(35, 0.26); //使用接受两个值的构造函数
Stonewt four = 190.36; //使用接受一个double值的构造函数
cout << "Show one:\n";
cout << one;
one.set_model_POU();
cout << one;
one.set_model_FLO();
cout << one;
one.set_model_STO();
cout << one;
cout << "Show two:\n";
cout << two;
two.set_model_FLO();
cout << two;
two.set_model_STO();
cout << two;
two.set_model_POU();
cout << two;
cout << "Show three:\n";
cout << three;
three.set_model_POU();
cout << three;
three.set_model_STO();
cout << three;
three.set_model_FLO();
cout << three;
cout << "Show four:\n";
cout << four;
four.set_model_FLO();
cout << four;
four.set_model_STO();
cout << four;
four.set_model_POU();
cout << four;
Stonewt sum_two_three = two + three;
Stonewt minus_three_four = three - four;
Stonewt mult_two = two * 2;
Stonewt mult_three = 3 * three;
cout << "Show sum_two_three:\n";
cout << sum_two_three;
cout << "Show minus_three_four:\n";
cout << minus_three_four;
cout << "Show mult_two:\n";
cout << mult_two;
cout << "Show mult_three:\n";
cout << mult_three;
return 0;
}
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）。
[code]// 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
[code]// 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;
}
// 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) const
{
if (pounds < s.pounds)
return true;
else
return false;
}
bool Stonewt::operator<=(const Stonewt & s) const
{
if (pounds <= s.pounds)
return true;
else
return false;
}
bool Stonewt::operator>(const Stonewt & s) const
{
if (pounds > s.pounds)
return true;
else
return false;
}
bool Stonewt::operator>=(const Stonewt & s) const
{
if (pounds >= s.pounds)
return true;
else
return false;
}
bool Stonewt::operator==(const Stonewt & s) const
{
if (pounds == s.pounds)
return true;
else
return false;
}
bool Stonewt::operator!=(const Stonewt & s) const
{
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";
}
[code]//usestonewt.cpp
#include <iostream>
#include "stonewt.h"
using namespace std;
int main()
{
Stonewt array[6] = {123.56, Stonewt(12, 0.35), Stonewt(15, 0)};
double input;
Stonewt const11 = Stonewt(11, 0);
Stonewt max = array[0];
Stonewt min = array[0];
int num = 0;
for (int i = 3; i < 6; i++)
{
cout << "请输入第" << i+1 << "个元素的pounds值：" ;
cin >> input;
array[i] = Stonewt(input);
cin.get();
}
for (int i = 0; i < 6; i++)
{
if (max < array[i])
max = array[i];
if (min > array[i])
min = array[i];
if (array[i] > const11)
num++;
}
for (int i = 0; i < 6; i++)
{
cout << "第" << i+1 << "个：\n";
array[i].show_stn();
array[i].show_lbs();
cout << endl;
}
cout << "最大：\n";
max.show_stn();
max.show_lbs();
cout << endl;
cout << "最小：\n";
min.show_stn();
min.show_lbs();
cout << endl;
cout << "超过11英石的有：" << num << "个\n";
return 0;
}
7. 复数由两个部分组成：实数部分和虚数部分。复数的一种书写方式是：(3.0, 4.0)，其中，3.0 是实数部分。4.0 是虚数部分。
假设a=(A,Bi)，c=(C,Di)，则下面是一些复数运算
·加法： a+c=(A+C,(B+D)i)
·减法： a-c=(A+C,(B+D)i)
·乘法： a*c=(A*C-B*D,(A*D+B*C)i)
·数乘： x*c=(x*C,x*Di)
·共轭： ~a=(A,-Bi)
请定义一个复数类，以便下面的程序可以使用它来获得正确的结果。
#include <iostream>
using namespace std;
#include "complex0.h" // to avoid confusion with complex.h
int main()
{
complex a(3.0, 4.0); // initialize to (3,4i)
complex 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";
return 0;
}
注意，必须重载运算符<<和>>。标准C++头文件complex提供了比这个示例更广泛的复数支持，
因此应将自定义的头文件命名为complex0.h，以免发生冲突。应尽可能使用const。
下面是该程序的运行情况。
Enter a complex number (q to quit):
real: 10
imaginary: 12
c is (10,12i)
complex conjugate is (10,-12i)
a is (3,4i)
a + c is (13,16i)
a - c is (-7,-8i)
a * c is (-18,76i)
2 * c is (20,24i)
Enter a complex number (q to quit):
real: q
Done!
请注意，经过重载后，cin>>c将提示用户输入实数部分和虚数部分。
[code]//complex0.h
#ifndef COMPLEX0_H_
#define COMPLEX0_H_
class Complex0
{
private:
double realpart; //实部
double imagpart; //虚部
public:
Complex0(double realnum = 0, double imagnum = 0);
~Complex0();
Complex0 operator+(const Complex0 & c) const;
Complex0 operator-(const Complex0 & c) const;
Complex0 operator*(const Complex0 & c) const;
friend Complex0 operator*(double x, const Complex0 & c);
friend Complex0 operator~(const Complex0 & c);
friend std::istream & operator>>(std::istream & ins, Complex0 & c);
friend std::ostream & operator<<(std::ostream & os, const Complex0 & c);
};
#endif
[code]//complex0.cpp
#include <iostream>
#include "Complex0.h"
Complex0::Complex0(double realnum, double imagnum)
{
realpart = realnum;
imagpart = imagnum;
}
Complex0::~Complex0()
{
}
Complex0 Complex0::operator+(const Complex0 & c) const
{
Complex0 temp;
temp.realpart = realpart + c.realpart;
temp.imagpart = imagpart + c.imagpart;
return temp;
}
Complex0 Complex0::operator-(const Complex0 & c) const
{
Complex0 temp;
temp.realpart = realpart - c.realpart;
temp.imagpart = imagpart - c.imagpart;
return temp;
}
Complex0 Complex0::operator*(const Complex0 & c) const
{
Complex0 temp;
temp.realpart = realpart * c.realpart - imagpart * c.imagpart;
temp.imagpart = realpart * c.imagpart + imagpart * c.realpart;
return temp;
}
Complex0 operator*(double x, const Complex0 & c)
{
Complex0 temp;
temp.realpart = x * c.realpart;
temp.imagpart = x * c.imagpart;
return temp;
}
Complex0 operator~(const Complex0 & c)
{
Complex0 temp;
temp.realpart = c.realpart;
temp.imagpart = -1 * c.imagpart;
return temp;
}
std::istream & operator>>(std::istream & ins, Complex0 & c)
{
std::cout << "real: ";
if (!(ins >> c.realpart))
return ins;
std::cout << "imaginary: ";
ins >> c.imagpart;
return ins;
}
std::ostream & operator<<(std::ostream & os, const Complex0 & c)
{
os << "(" << c.realpart << ", " << c.imagpart << "i)";
return os;
}
[code]//usecomplex0.cpp
#include <iostream>
using namespace std;
#include "complex0.h" // to avoid confusion with complex.h
int main()
{
Complex0 a(3.0, 4.0); // initialize to (3,4i)
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";
return 0;
}
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