实验5 多态性与虚函数
实验步骤：
第一步：
#include<iostream>
#include<cstdlib>
using namespace std;
class Rational
{
private:
//定义一个有理数num为分母，den为分子
long num,den;
public:
//构造函数
Rational(int num=0,int denom=1);
//重载比较操作符
int operator<(Rational r) const;
int operator<=(Rational r) const;
int operator==(Rational r) const;
int operator!=(Rational r) const;
};
Rational::Rational(int p,int q):num(p),den(q)
{
if(den==0)
{
cout<<"A Zero denominator is invalid"<<endl;
exit(1);
}
}
//重载“小于”
int Rational::operator<(Rational r) const
{
return num*r.den<r.num*den;
}
//重载“小于等于”
int Rational::operator<=(Rational r) const
{
return num*r.den<=r.num*den;
}
//重载“相等”
int Rational::operator==(Rational r) const
{
return num*r.den==r.num*den;
}
//重载“不相等”
int Rational::operator!=(Rational r) const
{
return num*r.den!=r.num*den;
}
int main()
{
Rational a(2,3),b(3,4);
if(a<b) cout<<"\na<b";
else cout<<"\na>b";
return 0;
}
第二步：Animal类的调试。
#include<iostream>
#include<cstring>
using namespace std;
class Animal{
protected:
char *name;
public:
Animal()
{
name=NULL;
}
Animal(char *n);
~Animal() {delete name;}
virtual void Identify();
};
Animal::Animal(char *n)
{
name=new char[strlen(n)+1];
strcpy(name,n);
}
void Animal::Identify()
{
cout<<"\ngeneric animal";
}
int main()
{
Animal a(" ");
a.Identify();
return 0;
}
第三步：Cat和Dog类的调试。
#include<iostream>
#include<cstring>
using namespace std;
class Animal{
protected:
char *name;
public:
Animal()
{
name=NULL;
}
Animal(char *n);
~Animal() {delete name;}
virtual void Identify();
};
class Cat:public Animal{
public:
Cat():Animal(){};
Cat(char *n):Animal(n){};
void Identify();
};
class Dog:public Animal{
public:
Dog():Animal(){};
Dog(char *n):Animal(n){};
void Identify();
};
Animal::Animal(char *n)
{
name=new char[strlen(n)+1];
strcpy(name,n);
}
void Animal::Identify()
{
cout<<"\ngeneric aninal";
}
void Cat::Identify()
{
cout<<"\nI am a cat named "<<name<<endl;
}
void Dog::Identify()
{
cout<<"\nI am a dog named "<<name<<endl;
}
int main()
{
Cat cat("Herry");
cat.Identify();
Dog dog("Jimmy");
dog.Identify();
return 0;
}
第四步：Tiger类的调试，Tiger类继承了Cat类。
#include<iostream>
#include<cstring>
using namespace std;
class Animal{
protected:
char *name;
public:
Animal()
{
name=NULL;
}
Animal(char *n);
~Animal() {delete name;}
virtual void Identify();
};
class Cat:public Animal{
public:
Cat():Animal(){};
Cat(char *n):Animal(n){};
void Identify();
};
class Tiger:public Cat{
public:
Tiger():Cat(){};
Tiger(char *n):Cat(n){};
void Identify();
};
class Dog:public Animal{
public:
Dog():Animal(){};
Dog(char *n):Animal(n){};
void Identify();
};
Animal::Animal(char *n)
{
name=new char[strlen(n)+1];
strcpy(name,n);
}
void Animal::Identify()
{
cout<<"\ngeneric aninal";
}
void Cat::Identify()
{
cout<<"\nI am a cat named "<<name<<endl;
}
void Tiger::Identify()
{
cout<<"\nI am a tiger named "<<name<<endl;
}
void Dog::Identify()
{
cout<<"\nI am a dog named "<<name<<endl;
}
int main()
{
Cat cat("Herry");
cat.Identify();
Dog dog("Jimmy");
dog.Identify();
Tiger tiger("Richard");
tiger.Identify();
return 0;
}
#include<iostream>
using namespace std;
class Animal{
protected:
char *name;
public:
Animal()
{
name=NULL;
}
Animal(char *n);
~Animal() {delete name;}
virtual void Identify();
};
class Cat:public Animal{
public:
Cat():Animal(){};
Cat(char *n):Animal(n){};
void Identify();
};
class Tiger:public Cat{
public:
Tiger():Cat(){};
Tiger(char *n):Cat(n){};
void Identify();
};
class Dog:public Animal{
public:
Dog():Animal(){};
Dog(char *n):Animal(n){};
void Identify();
};
第五步：增加Zoo类。
#include<iostream>
#include<cstring>
using namespace std;
class Animal{
protected:
char *name;
public:
Animal()
{
name=NULL;
}
Animal(char *n);
~Animal() {delete name;}
virtual void Identify();
};
class Cat:public Animal{
public:
Cat():Animal(){};
Cat(char *n):Animal(n){};
void Identify();
};
class Tiger:public Cat{
public:
Tiger():Cat(){};
Tiger(char *n):Cat(n){};
void Identify();
};
class Dog:public Animal{
public:
Dog():Animal(){};
Dog(char *n):Animal(n){};
void Identify();
};
class Zoo
{
private:
unsigned int maxanimals; //动物园最多能圈养的动物数
unsigned int numanimals; //动物园当前圈养的动物数
Animal **residents; //指向动物园圈养的动物对象的指针数组
public:
Zoo(unsigned int max); //构造函数，max为最多能圈养动物数
~Zoo(){delete residents;} //析构函数
unsigned int Accept(Animal *d);//接收动物
void ListAnimals(); //显示动物园所有动物
};
Animal::Animal(char *n)
{
name=new char[strlen(n)+1];
strcpy(name,n);
}
void Animal::Identify()
{
cout<<"\ngeneric aninal";
}
void Cat::Identify()
{
cout<<"\nI am a cat named "<<name<<endl;
}
void Tiger::Identify()
{
cout<<"\nI am a tiger named "<<name<<endl;
}
void Dog::Identify()
{
cout<<"\nI am a dog named "<<name<<endl;
}
Zoo::Zoo(unsigned int max)
{
maxanimals=max;
numanimals=0;
residents=new Animal *[maxanimals]; //分配空间
for(int i=0;i<maxanimals;i++) // 指针清空
residents[i]=NULL;
}
unsigned int Zoo::Accept(Animal *d)
{
if(numanimals==maxanimals) //超过最大圈养数
return 0;
++numanimals; //当前圈养数加1
int i=0;
while(residents[i]!=NULL) //指针指向接收的动物对象
{
++i;
}
residents[i]=d;
return ++i;
}
void Zoo::ListAnimals()
{
cout<<"\n (: There are ";
cout<<numanimals<<" animals in Zoo.\n";//显示动物园总的动物数
if(numanimals>0)
for(int i=0;i<maxanimals;++i)
if(residents[i]!=NULL)
residents[i]->Identify(); //显示动物对象的名称和种类
}
int main()
{
Cat cat("Herry"),*q;
cat.Identify();
Dog dog("Jimmy"),*p;
dog.Identify();
Tiger tiger("Richard"),*r;
tiger.Identify();
Zoo beiging(20);
q=&cat;
p=&dog;
r=&tiger;
unsigned i=beiging.Accept(p);
beiging.ListAnimals();
i=beiging.Accept(q);
beiging.ListAnimals();
i=beiging.Accept(r);
beiging.ListAnimals();
return 0;
}
日期：2020年3月25日
