运算符重载和多态性

实验5 运算符重载和多态性班级学号（最后两位）姓名成绩

一、实验目的

1．掌握用成员函数重载运算符的方法

2．掌握用友元函数重载运算符的方法

3．理解并掌握利用虚函数实现动态多态性和编写通用程序的方法

4．掌握纯虚函数和抽象类的使用

二、实验内容

1．复数类加减法乘除运算(用成员函数定义运算符重载)。

复数类的定义：

class complex //复数类声明

{ public: //外部接口

complex(double r=0.0,double i=0.0) //构造函数

{real=r,imag=i;}

complex operator +(complex c2); //运算符"+"重载成员函数

complex operator - (complex c2); //运算符"-"重载成员函数

complex operator *(complex ); //运算符"*"重载成员函数

complex operator /(complex); //运算符"/"重载成员函数

complex operator =(complex c2); //运算符"="重载成员函数

void display(); //输出复数

private: //私有数据成员

double real; //复数实部

double imag; //复数虚部

};

实验代码：

#include

using namespace std;

class Complex

{

public:

Complex()

{

real=0;

imag=0;

}

Complex(double r,double i)

{

real=r;

imag=i;

}

Complex operator+(Complex &c2);

Complex operator-(Complex &c2);

Complex operator*(Complex &c2);

Complex operator/(Complex &c2);

void display();

private:

double real; double imag;

};

Complex Complex::operator+(Complex &c2)

{

Complex c;

c.real=real+c2.real;

c.imag=imag+c2.imag; return c;

}

Complex Complex::operator-(Complex &c2)

{

Complex c;

c.real=real-c2.real;

c.imag=imag-c2.imag;

return c;

}

Complex Complex::operator*(Complex &c2)

{

Complex c;

c.real=real*c2.real-imag*c2.imag;

c.imag=imag*c2.real+real*c2.imag; return c;

}

Complex Complex::operator/(Complex &c2)

{

Complex c;

c.real=(real*c2.real+imag*c2.imag)/(c2.real*c2.real+c2.imag*c2.imag);

c.imag=(imag*c2.real-real*c2.imag)/(c2.real*c2.real+c2.imag*c2.imag);

return c;

}

void Complex::display()

{cout<<"("<

int main()

{

Complex c1(4,7),c2(2,1),c3;

cout<<"c1=";

c1.display();

cout<<"c2=";

c2.display();

int i,j=1;

while(j)

{

cout<<"\n";

cout<<"\t\t"<<"1.复数之和\n";

cout<<"\t\t"<<"2.复数之差\n";

cout<<"\t\t"<<"3.复数之积\n";

cout<<"\t\t"<<"4.复数之商\n";

cout<<"\t\t"<<"0.退出\n";

cout<<"请选择（0－－4） ";

cin>>i;

switch(i)

{

case 1: c3=c1+c2;

cout<<"c1+c2=";c3.display();

break;

case 2: c3=c1-c2;

cout<<"c1-c2=";

c3.display();break;

case 3: c3=c1*c2;

cout<<"c1*c2=";

c3.display();

break;

case 4: c3=c1/c2;

cout<<"c1/c2=";

c3.display();

break;

case 0: j=0;

break;

}

}

}

实验测试：

2．复数类比较运算(用友元函数定义运算重载)。

注意：

1）复数类比较运算按复数的模比较两个复数的大小。

2）复数相等判断当两个复数的实部和虚部都相等，两个复数才相等，否则不相等。

类的定义

class complex //复数类声明

{

public:

complex(double r=0.0,double i=0.0)

{real=r;imag=i;} //构造函数

friend int operator> (complex c1,complex c2); //运算符">"重载友元函数

friend int operator>=(complex c1,complex c2); //运算符">="重载友元函数

friend int operator <(complex c1,complex c2); //运算符"<"重载友元函数

friend int operator<=(complex c1,complex c2); //运算符"<="重载友元函数

friend int operator ==(complex c1,complex c2); //运算符"=="重载友元函数

friend int operator !=(complex c1,complex c2); //运算符"!="重载友元函数void display( ); //显示复数的值

private: //私有数据成员

double real;

double imag;

};

实验代码：

#include"iostream.h"

#include"math.h"

class complex

{

public:

complex(double r=0.0,double i=0.0)

{

real=r;imag=i;

}

friend bool operator> (complex c1,complex c2);

friend bool operator>=(complex c1,complex c2);

friend bool operator< (complex c1,complex c2);

friend bool operator<=(complex c1,complex c2);

friend bool operator==(complex c1,complex c2);

friend bool operator!=(complex c1,complex c2);

void display( );

private:

double real;

double imag;

};

bool operator>(complex c1,complex c2)

{

if(sqrt(c1.real*c1.real+c1.imag*c1.imag)>sqrt(c2.real*c2.real+c2.imag*c2.imag))

return true;

else

return false;

}

bool operator>=(complex c1,complex c2)

{

if(sqrt(c1.real*c1.real+c1.imag*c1.imag)>sqrt(c2.real*c2.real+c2.imag*c2.imag)||sqrt(c1.real*c1.r eal+c1.imag*c1.imag)==sqrt(c2.real*c2.real+c2.imag*c2.imag))

return true;

else

return false;

}

bool operator<(complex c1,complex c2)

{

if(sqrt(c1.real*c1.real+c1.imag*c1.imag)

return true;

else

return false;

}

bool operator<=(complex c1,complex c2)

{

if(sqrt(c1.real*c1.real+c1.imag*c1.imag)

return true;

else

return false;

}

bool operator==(complex c1,complex c2)

{

if(c1.real==c2.real&&c1.imag==c2.imag)

return true;

else

return false;

}

bool operator!=(complex c1,complex c2)

{

if(c1.real!=c2.real||c1.imag!=c2.imag) return true;

else

return false;

}

void complex::display()

{

cout<<"("<

}

void compare(complex &c1,complex &c2)

{

if(operator>(c1,c2)==1)

{c1.display();cout<<">";c2.display(); cout<=(c1,c2)==1)

{c1.display();cout<<">=";c2.display(); cout<

{c1.display();cout<<"<";c2.display(); cout<

{c1.display();cout<<"<=";c2.display(); cout<

{c1.display();cout<<"=";c2.display(); cout<

{c1.display();cout<<"!=";c2.display(); cout<

int main() {

complex c1(2,8),c2(3,6),c3(4,5);

cout<<"c1=";c1.display();

cout<

cout<<"c2=";c2.display();

cout<

cout<<"c3=";

c3.display();

cout<

compare(c1,c2);

compare(c1,c3);

compare(c2,c3);

return 0;

}

测试结果：

3．利用虚函数实现的多态性来求四种几何图形的面积之和。这四种几何图形是：三角形、矩形、正方形和圆。几何图形的类型可以通过构造函数或通过成员函数来设置。

⑴分析

计算这四种几何图的面积公式分别是：

三角形的边长为W，高为H时，则三角形的面积为W* H/2；矩形的边长为W，宽为H 时，则其面积为W* H；正方形的边长为S，则正方形的面积为S*S；圆的半径为R，其面积为3.1415926 *R *R。

为设置几何图形的数据并求出几何图形的面积，需要定义一个包含两个虚函数的类：class Shape

{public:

virtual float Area( void) =0; //求面积

virtual void Setdata(float ,float =0) =0; //设置图形数据

};

因面积的计算依赖于几何图形，故在类中只能定义一个纯虚函数Area。同理，设置几何图形数据的函数Setdata也只能定义为纯虚函数。

把这个基类派生出其它几何图形类。如派生出的三角形类为：

class Triangle:public Shape

{ float W,H; //三角形边长为W，高为H

public:

Triangle(float w=0,float h=0){ W=w; H = h; }

float Area( void){ return W*H/2; }

void Setdata(float w,float h=0){ W=w; H = h; }

};

实验代码：

#include

#define PI 3.1415926

using namespace std;

class Shape

{ public:

virtual float Area( void) =0;

virtual void show(void) =0;

};

class Triangle:public Shape

{ float W,H;

public:

Triangle(float w=0,float h=0){ W=w; H = h; }

float Area( void){ return W*H/2; }

void show()

{ cout<<"\n三角形:"<<" 边长:"<

}

};

class Rectangle:public Shape

{

float W,H;

public:

Rectangle(float w=0,float h=0):W(w),H(h){}

float Area(void){ return W*H; }

void show()

{ cout<<"\n\n矩形:"<<" 长:"<

<<" 矩形面积面积:"<

};

class Square:public Shape

{

float W;

public:

Square(float w=0):W(w){}

float Area(void){ return W*W; }

void show()

{ cout<<"\n\n正方形:"<<" 边长:"<

};

class Circle:public Shape

{

float radius;

public:

Circle(float r):radius(r){}

float Area(void){ return PI*radius*radius; }

void show()

{ cout<<"\n\n圆:"<<" 半径:"<

void main()

{ Shape *S;

Triangle T(1,4);

Rectangle R(6,2);

Square Sq(4);

Circle C(7);

S=&T; S->show();

S=&R; S->show();

S=&Sq; S->show();

S=&C; S->show();

}

测试结果：