程序的疑问，请大家解疑 - C++教室 - C++论坛

上山打老鼠

等　级：新手上路
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注　册：2006-1-13

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程序的疑问，请大家解疑

请大家看看这个程序

这是一个菜单，实现插入、删除、修改和输出等操作。
有几个弱弱的问题要请教大家，程序如下：
#include <iostream.h>
#include <string.h>
template<class T>
class List
{protected:
T *first;//链表头指针
public:
List(){first=NULL;}
void Insert(T &elem) //表头插入
{ if(first==NULL) //若表为空
{first=&elem;elem.next=NULL;}
else
{elem.next=first;first=&elem;}
}
void Dle(int Jd) //删除结点
{ T *p;
if(first==NULL) return;//表为空
if(first->key()== Jd)//删除头结点
{T *x=first; x->print(); first=first->next; delete x;}
else //不是头结点
{for(T *q=first;q->next!=NULL;q=q->next)
if(q->next->key()==Jd)
{T *x=q->next; x->print(); p=q->next; q->next=p->next;
delete x;
return;}
}
}
void Print()
{ for(T *p=first;p;p=p->next)
{ p->print(); cout<<endl;}
}
};
class type_base
{protected:
int number;
char name[15],sex[4],data_of_birthday[12];
public:
type_base *next;
virtual void print(); //运算符重载
virtual istream& operator>>(istream &dest);
int key()
{return number;}
};
istream & type_base::operator>>(istream &dest)
{ cout<<"请输入学号，姓名，性别，出生日期"<<endl;
dest>>number>>name>>sex>>data_of_birthday;
return dest;
}
void type_base::print( )
{ cout<<"调用基类的输出。";
cout<<number<<name<<sex<<data_of_birthday;
}
class student:public type_base
{protected:
double goal;
public:
istream & operator>>(istream &dest);
void print()
{ cout<<"学生:";
cout<<"("<<number<<" "<<name<<" "<<sex<<" "<<data_of_birthday<<" "<<")"<<endl;
}
};
istream & student::operator>>(istream &dest)
{ cout<<"请输入学号，姓名，性别，出生日期："<<endl;
dest>>number>>name>>sex>>data_of_birthday;
return dest;
}
class staff:public type_base
{protected:
char office[20];
public:
istream & operator>>(istream &dest);
void print()
{cout<<"员工:";
cout<<"("<<number<<" "<<name<<" "<<sex<<" "<<data_of_birthday<<" "<<")"<<endl;
}
};
istream & staff::operator>>(istream &dest)
{cout<<"请输入员工号，姓名，性别，出生日期："<<endl;
dest>>number>>name>>sex>>data_of_birthday;
return dest;
}
class teacher:public type_base
{protected:
double fund;
public:
istream & operator>>(istream &dest);
void print()
{cout<<"老师:";
cout<<"("<<number<<" "<<name<<" "<<sex<<" "<<data_of_birthday<<" "<<")"<<endl;
}
};
istream & teacher::operator>>(istream &dest)
{ cout<<"请输入员工号，姓名，性别，出生日期："<<endl;
dest>>number>>name>>sex>>data_of_birthday;
return dest;
}
void display1()
{ cout<<"\n(1) 增加数据.\n";
cout<<"(2) 删除数据.\n";
cout<<"(3) 显示数据.\n";
cout<<"(4) 结束.\n";
cout<<"请选择...";
}
void display2()
{ cout<<"1.学生.\n";
cout<<"2.职工.\n";
cout<<"3.教师.\n";
}
void main()
{ List<type_base> list;
int ch;
while(ch!=4)
{ display1();
cin>>ch;
if(ch==1)
{int ah; display2(); cin>>ah;
if(ah==1)
{student *p=new student;
(*p)>>cin;
list.Insert(*p);
list.Print();
}
else if(ah==2)
{staff *p=new staff;
(*p)>>cin;
list.Insert(*p);
list.Print();
}
else
{teacher *p=new teacher;
(*p)>>cin;
list.Insert(*p);
list.Print();
}
}
else if(ch==2)
{int ax;
cout<<"输入要删除的编号:";
cin>>ax;
cout<<endl;
list.Dle(ax);
cout<<"删除后为:\n";
list.Print();
}
else if(ch==3) list.Print();
}
}
问题也补上，头文件里的template<class T>是什么意思？
还有第39行的注释哪个是重载运算符？执行了什么重载运算？
那一个模块有什么作用？还有下面的
istream & type_base::operator>>(istream &dest)
{ cout<<"请输入学号，姓名，性别，出生日期"<<endl;
dest>>number>>name>>sex>>data_of_birthday;
return dest;
又有什么作用？请大家指教！不胜感激！！

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2006-01-13 11:13

上山打老鼠

等　级：新手上路
帖　子：3
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注　册：2006-1-13

第 3 楼

得分:0

可是我觉得

class type_base
{protected:
int number;
char name[15],sex[4],data_of_birthday[12];
public:
type_base *next;
virtual void print(); //运算符重载
virtual istream& operator>>(istream &dest);
int key()
{return number;}
};

这里不叫运算符重载,而是虚函数,virtual的意思是代表继承类可以实现自己的函数体.

staff中就实现了相同名字的print

class staff:public type_base
{protected:
char office[20];
public:
istream & operator>>(istream &dest);
void print()
{cout<<"员工:";
cout<<"("<<number<<" "<<name<<" "<<sex<<" "<<data_of_birthday<<" "<<")"<<endl;
}
};

istream & type_base::operator>>(istream &dest)

才是重载操作符:">>"
（是这样么？）

啊啊啊，头大。。。。

2006-01-13 15:18