西安交大C++程序设计第十章作业

西安交通大学实验报告课程__计算机程序设计__实验名称__多态性__第 1 页共 44 页系别____ ______ 实验日期 2014 年 5 月 31 日专业班级__ ____组别_____________ 实验报告日期 2014 年 5 月 31 日姓名___ _____学号_ _报告退发 ( 订正、重做 )同组人_________________________________ 教师审批签字一、实验目的理解掌握多态的使用方法，学会用虚函数。

二、实验内容（一）第一题：定义一个类Base，该类含有虚函数display，然后定义它的两个派生类FirstB和SecondB，这两个派生类均含有公有成员函数display，在主程序中，定义指向基类Base的指针变量ptr，并分别定义Base、FirstB、Second的对象b1、f1、s1，让ptr分别指向b1、f1、s1的起始地址，然后指向执行这些对象的成员函数display。

1.源程序代码：#include<iostream>using namespace std;class Base{public:virtual void display(){cout<<"sound!sound!sound!";}};class FirstB:public Base{public:void virtual display(){cout<<"miao!miao!miao!";}};class SecondB:public Base{public:void virtual display(){cout<<"wang!wang!wang!";}};int main(){Base *ptr;Base b1;FirstB f1;SecondB s1;cout<<"指向基类Base:\t";ptr=&b1;ptr->display();cout<<"\n指向派生类FirstBase：\t";ptr=&f1;ptr->display();cout<<"\n指向派生类SecondB：\t";ptr=&s1;ptr->display();cout<<endl;return 0;}2.实验结果：（二）第二题：扩充例10-5，从中派生一个正方形类和圆柱体类，写一个测试程序，输出正方形的面积和圆柱体的体积。

1.源程序代码：//shape类shape.h文件#ifndef SHAPE_H#define SHAPE_H#include<iostream>using namespace std;class Shape{public:virtual double Area()const{return 0.0;}//纯虚函数，在派生类中重载virtual double Volume() const=0;virtual void PrintShapeName() const=0;virtual void Print() const=0;};#endif//point.h点类#ifndef POINT_H#define POINT_H#include"shape.h"using namespace std;class Point:public Shape{int x,y;public:Point(int a=0,int b=0){SetPoint(a,b);}void SetPoint(int a,int b){x=a;y=b;}int GetX(){return x;}int GetY(){return y;}virtual double Volume() const{return 0.0;}virtual void PrintShapeName()const {cout<<"Point:";}virtual void Print()const{cout<<'['<<x<<","<<y<<']';}};#endif//circle.h圆类#ifndef CIRCLE_H#define CIRCLE_H#include<iostream>using namespace std;class Circle:public Point{double radius;public:Circle(int x=0,int y=0,double r=0.0):Point(x,y) {SetRadius(r);}void SetRadius(double r){radius=(r>=0?r:0);}double GetRadius() const{return radius;}virtual double Area() const{return 3.14159*radius*radius;}virtual double Volume() const{return 0.0;}virtual void PrintShapeName() const{cout<<"Circle:";}void Print() const{cout<<"Center=";Point::Print();cout<<";Radius="<<radius<<endl;}};#endif//rectangle.h矩形类#ifndef RECTANGULAR_H#define RECTANGULAR_H#include<iostream>using namespace std;class Rectangle:public Point{double length,width;public:Rectangle(int x=0,int y=0,double l=0.0,double w=0.0):Point(x,y) {SetLength(l);SetWidth(w);}void SetLength(double l){length=(l>=0?l:0);}void SetWidth(double w){width=(w>=0?w:0);}double GetLength() const{return length;}double GetWidth() const{return width;}virtual double Area() const{return length*width;}virtual double Volume() const{return 0.0;}virtual void Print() const{cout<<"Left Top Vertex=";Point::Print();cout<<";Length="<<length<<",Width="<<width<<endl;}virtual void PrintShapeName() const{cout<<"Rectangle:";}};#endif//cylinder.h圆柱体类#ifndef CYLINDER_H#define CYLINDER_H#include"circle.h"#include<iostream>;using namespace std;class Cylinder:public Circle{double height;public:Cylinder(int x=0,int y=0,double r=0,double h=0):Circle(x,y,r) {SetHeight(h);}void SetHeight(double h){height=(h>=0?h:0);}double GetHeight() const{return height;}double Volume() const{return Area()*height;}virtual void PrintShapeName() const{cout<<"Cylinder:";}void Print() const{Circle::Print();cout<<"Height="<<height<<endl;}};#endif//square.h正方形类，几乎跟矩形类一样而已#ifndef SQUARE_H#define Square_H#include"rectangle.h"#include<iostream>using namespace std;class Square:public Rectangle{double sidelength;public:Square(int x=0,int y=0,double s=0.0):Rectangle(x,y) {Seta(s);}void Seta(double s){sidelength=s;}virtual double Area() const{return sidelength*sidelength;}virtual double Volume() const{return 0.0;}virtual void Print() const{cout<<"Left Top Vertex=";Point::Print();cout<<";Length="<<sidelength<<endl;}virtual void PrintShapeName() const{cout<<"Square:";}};#endifmain.h//要求：派生出圆柱类和正方形类，计算面积、体积#include<iostream>#include"shape.h"#include"point.h"#include"circle.h"#include"rectangle.h"#include"square.h"#include"cylinder.h"using namespace std;//为何系统报错提示要输入一个“;”在此句首void virtualViaPointer(const Shape*);void virtualViaReference(const Shape&);int main(){//创建point circle rectangular对象信息Point point(30,50);Circle circle(120,80,10.0);Rectangle rectangle(10,10,8.0,5.0);Square square(10,20,5.0);Cylinder cylinder(120,80,10.0,40.0);//输出point circle rectangular 对象信息point.PrintShapeName();point.Print();cout<<endl;circle.PrintShapeName();circle.Print();rectangle.PrintShapeName();rectangle.Print();square.PrintShapeName();square.Print();cylinder.PrintShapeName();cylinder.Print();//定义基类对象指针Shape *arrayOfShapes[5];//定义了个基类指针arrayOfShapes[0]=&point;arrayOfShapes[1]=&circle;arrayOfShapes[2]=&rectangle;arrayOfShapes[3]=&square;arrayOfShapes[4]=&cylinder;//通过基类对象指针访问派生类对象cout<<"Virtual function calls made off"<<"base-class pointers\n";for(int i=0;i<5;i++)virtualViaPointer(arrayOfShapes[i]);cout<<"Virtual function calls made off"<<"base-case references\n";for(int j=0;j<5;j++)virtualViaReference(*arrayOfShapes[j]);return 0;}//通过基类对象访问虚函数实现动态绑定void virtualViaPointer(const Shape*baseClassPtr){baseClassPtr->PrintShapeName();baseClassPtr->Print();cout<<"Area="<<baseClassPtr->Area();cout<<"\tVolume="<<baseClassPtr->Volume()<<endl; }//通过基类对象引用访问虚函数实现动态绑定void virtualViaReference(const Shape &baseClassRef) {baseClassRef.PrintShapeName();baseClassRef.Print();cout<<"Area="<<baseClassRef.Area();cout<<"\tVolume="<<baseClassRef.Volume()<<endl; }2.实验结果：（三）第三题：扩充实例编程中的日期类，为Date增加一个成员函数，可以判断日期是否为系统当前日期。