淮海工学院计算机科学系
实验报告书
课程名：《 C++程序设计(二)》
题 目： 多态性和虚函数
班 级：
学 号：
姓 名：
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1. 实验内容或题目
（1）声明二维坐标类作为基类派生圆的 类，把派生类圆作为基类，派生圆柱体类。其中，基类二维坐标类有成员数据：x、y坐标值；有成员函数：构造函数实现对基类成员数据的初始化、输出的成员函数，要求输出坐标位置。派生类圆类有新增成员数据：半径（R）；有成员函数：构造函数实现对成员数据的初始化、计算圆面积的成员函数、输出半径的成员函数。派生圆柱体类新增数据有高（H）；新增成员函数有构造函数、计算圆柱体体积的函数和输出所有成员的函数。请完成程序代码的编写、调试。
（2）教材393页7－8题。
（3）教材416页1、4、5题。
2. 实验目的与要求
（1）理解继承与派生的概念
（2）掌握通过继承派生出一个新的类的方法
（3）了解多态性的概念
（4）了解虚函数的作用与使用方法
⑵ 源代码
（1）#include<iostream>
using namespace std;
class point
{ public:
point(float a=0,float b=0);
void setpoint(float,float);
float get_x()const{return x;}
float get_y()const{return y;}
friend ostream &operator<<(ostream &, point &);
protected: float x,y;
};
point::point(float a,float b)
{ x=a;
y=b;
}
void point::setpoint(float a,float b)
{ x=a;
y=b;
}
ostream &operator<<(ostream &output,const point&p)
{
output<<"["<<p.get_x()<<","<<p.get_y()<<"]"<<endl;
return output;
}
class circle:public point
{ public:
circle(float a=0,float b=0,float r=0):point(a,b),radius(r){}
float area()const{return 3.14*radius*radius;}
float getradius()const{return radius;}
protected: float radius; };
class cyl:public circle
{ public:
cyl(float a=0,float b=0,float r=0,float h=0):circle(a,b,r),height(h){}
float volume()const
{return 3.14*radius*radius*height;}
friend ostream &operator<<(ostream &, point &);
float getheight()const{return height;}
protected: float height;
};
ostream &operator<<(ostream &output,const cyl&cy)
{ output<<"["<<cy.get_x()<<","<<cy.get_y()<<"],"<<"h="<<cy.getheight()<<",volumn="<<cy.volume()<<endl;
return output;
}
int main()
{
point p(1,3);
circle c(1,2,3);
cyl cy(1,2,3,4);
cout<<"x="<<p.get_x()<<",y="<<p.get_y()<<endl;
cout<<"area="<<c.area()<<endl; cout<<"x="<<cy.get_x()<<",y="<<cy.get_y()<<",h="<<cy.getheight()<<",volume="<<cy. volume()<<endl;
return 0;
}
（2）7
#include <iostream>
using namespace std;
class A
{public:
A(){a=0;b=0;}
A(int i){a=i;b=0;}
A(int i,int j){a=i;b=j;}
void display(){cout<<"a="<<a<<"b="<<b;}
private:
int a;
int b;
};
class B : public A
{public:
B(){c=0;}
B(int i):A(i){c=0;}
B(int i,int j):A(i,j){c=0;}
B(int i,int j,int k):A(i,j){c=k;}
void display1()
{display();
cout<<"c="<<c<<endl;
}
private:
int c;
};
int main()
{
B b1;
B b2(1);
B b3(1,3);
B b4(1,3,5);
b1.display1();
b1.display1();
b1.display1();
b1.display1();
return 0;
}
（2）8
#include<iostream>
using namespace std;
class A
{ public:
A(){cout<<"constructing A"<<endl;}
~A(){cout<<"destrucing A"<<endl;}
};
class B:public A
{ public:
B(){cout<<"constructing B"<<endl;}
~B(){cout<<"destrucingB"<<endl;}
};
class C:public B
{ public:
C(){cout<<"constructing C"<<endl;}
~C(){cout<<"destrucing C"<<endl;}
};
int main()
{
C c1;
return 0;
}
（3） 1
头文件1
class Point
{ public:
Point(float a=0,float b=0);
void setPoint(float,float);
float get_X()const{return x;}
float get_Y()const{return y;}
friend ostream &operator<<(ostream &,const point &);
protected:
float x,y;
};
头文件2
class Circle:public point
{ public:
Circle(float a=0,float b=0,float r=0);
void setradius(float);
float area()const;
float getradius()const;
friend ostream &operator<<(ostream &,const Circle &);
protected:
float radius;
};
头文件3
class Cyl:public circle
{ public:
Cyl(float a=0,float b=0,float r=0,float h=0);
void setHeight(float);
float getHeight()const;
float area()const;
float volume()const;
friend ostream &operator<<(ostream &, const cyl &);
protected:
float height;
};
源文件1
#include<iostream.h>
#include"ex_1_1(head).h"
Point::Point(float a,float b)
{x=a; y=b; }
void Point::setPoint(float a,float b)
{ x=a; y=b; }
float point::get_x()const{return x;}
float point::get_y()const{return y;}
ostream &operator<<(ostream &output,const Point&p) { output<<"["<<p.x()<<","<<p.y()<<"]"<<endl;
return output;
}
源文件2
#include<iostream.h>
#include"ex_1_1(head).h"
#include"ex_1_1(head1).h"
Circle::Circle(float a ,float b ,float r ):Point(a,b),radius(r){}
void Circle::setRadius(float r){radius=r;}
float Circle::getRadius( )const{return radius;}
float Circle::area()const{return 3.14*radius*radius;}
ostream &operator<<(ostream &output,const Circle &c)
{
output<<"Center ["<<c.x<<","<<c.y<<"],r="<<c.radius<<",area="<<c.area()<<endl; return output;
}
源文件3
#include<iostream.h>
#include"ex_1_1(head).h"
#include"ex_1_1(head1).h"
#include"ex_1_1(head2).h"
Cylinder:: Cylinder (float a ,float b ,float r ,float h ):circle(a,b,r),height(h){}
void Cylinder::setHeight(float h){height=h;}
float Cylinder:: getHeight()const{return height;}
float Cylinder::area()const{return 2*Circle::area()+2*3.14*radius*height;}
float Cylinder::volume()const
{return Circle::area()*height;}
ostream &operator<<(ostream &output,const Cyl&cy) { output<<"Center="<<cy.x<<","<<cy.y<<"],"<<"h="<<cy.height<<"area="<<cy.area()<<",volumn="<<cy.volume()<<endl;
return output;
}
主函数
#include<iostream.h>
#include "ex_1_1(head).h"
#include "ex_1_1(head1).h"
#include "ex_1_1(head2).h"
int main()
{
Cylinder cy1 (1,2,3,4)
cout<<"\noriginal cylinder:\nx="<<cy1.getX()<<"y="<<cy1.getY()<",r="<<
<<cy1.getRadius()<<",h="<<cy1.getHeight()<<"\narea="<<cy1.area()<<",volume="<<cy1.volume()<<endl;
cy1.setHeught(15)
cy1.setRadius(7.5)
cy1.setPoint(5,5)
cout<<"\npref cylinder:\n"<<cy1;
Point &pRef=cy1;
cout<<"\npRef as Point:"<<pRef;
Circle &Ref=cy1;
cout<<"\npRef as Circle:"<<cRef;
return 0;
}
(3) 1
#include<iostream.h>
#include "ex_1_1(head).h"
#include "ex_1_1(head1).h"
#include "ex_1_1(head2).h"
int main()
{ point p(1,3);
circle c(1,2,3);
cyl cy(1,2,3,4);
cout<<"x="<<p.get_x()<<",y="<<p.get_y()<<endl;
cout<<"area="<<c.area()<<endl; cout<<"x="<<cy.get_x()<<",y="<<cy.get_y()<<",h="<<cy.getheight()<<",area="<<cy.area()<<",volume="<<cy. volume()<<endl;
return 0;
}
（3）4
#include<iostream>
using namespace std;
class shape
{ public:
virtual float PrintArea()
const{return 0.0;}
};
// http://www.pprar.com
class circle:public shape
{ public:
circle(float r=0);
void setradius(float);
float getradius( )const;
virtual float PrintArea()const;
protected: float radius;
};
circle::circle(float r){radius=r;}
void circle::setradius(float r) {radius=r;}
float circle::getradius()const{return radius;}
float circle:: PrintArea() const {return 3.14*radius*radius;}
int main()
{
circle cir(5);
cir.PrintArea();
shape *pt; pt=&cir ;
pt->PrintArea();
cout<<pt->PrintArea()<<endl;
return 0;
}
（3）5
#include<iostream>
#include<cmath>
using namespace std;
class shape
{ public:
virtual float PrintArea() const{return 0.0;}
};
class circle:public shape { public: circle(float r=0);
virtual float PrintArea()const;
protected: float radius;
};
circle::circle(float r) {radius=r;}
float circle:: PrintArea()
const {return 3.14*radius*radius;}
class rectangle:public shape
{ public:
rectangle(float a=0,float b=0);
virtual float PrintArea()const;
protected: float x,y;
};
rectangle:: rectangle(float a,float b)
{ x=a;y=b;}
float rectangle:: PrintArea() const {return x*y;}
class triangle:public shape
{ public:
triangle(float a=0,float b=0,float c=0);
virtual float PrintArea()const;
protected: float x,y, z ;
};
triangle::triangle (float a,float b,float c)
{ x=a;y=b;z=c;}
float triangle:: PrintArea() const {return x*y*sqrt(1-(x*x+y*y-z*z)*(x*x+y*y-z*z)/4*x*x*y*y)/2;}
int main()
{
circle cir(5);
rectangle rec(1,2);
triangle tri(3,4,5);
shape *pt[3];
pt[0]=○
pt[1]=&rec;
pt[2]=&tri;
cout<<pt[0]->PrintArea()<<endl;
cout<<pt[1]->PrintArea()<<endl;
cout<<pt[2]->PrintArea()<<endl;
return 0;
}
测试数据与实验结果（可以抓图粘贴）
（1）
（2）7
（2）8
（3）1
（3）4、 、
（3）5
结果分析与实验体会
这次作业运用书上给的例题加以结合便可轻而易举的完成，但是第二题我做了很长时间都没有做上来，每次改正之后都会残留一些小小的错误，最后用尽各种手段，终于把他搞了出来，但是我还是有一些地方不明白，都是自己不够用心，不够认真才坐不上来，今后要勤加学习，把不明白的搞懂。