#include<iostream.h>
#include<stdlib.h>

void Exception(int Condition,   char *ErrorMsg){
	if(Condition){cerr << ErrorMsg << endl; abort();}
}

template<class ElemType>
class AbsStack{
	public:
		AbsStack(){}  //默然构造函数
		virtual ~AbsStack(){}  //析构函数
		virtual bool IsEmpty() const = 0;  //判栈空
		virtual bool IsFull() const = 0;   //判栈满
		virtual void MakeEmpty() = 0;     //将栈清空
		virtual void Push( ElemType &x) = 0;  //进栈
		virtual void Pop() = 0;        //出栈
		virtual const ElemType &Top()  = 0; //取顶点元素
	private:
		AbsStack(const AbsStack &){};  //冻结复制构造函数
};

template<class ElemType>
class Stack;  //前向说明

template<class ElemType>
class ListNode{
	friend class Stack<ElemType>;  //便于访问结点的私有成员
	private:
		ListNode<ElemType> *Next;  //指向下一个结点
		ElemType Element;   //结点数据
	public:
		ListNode(const ElemType &E, ListNode<ElemType> *N = 0):Element(E), Next(N)
		{}; //构造函数
		ListNode():Next(0){}; //构造函数
		~ListNode(){};  //析构函数
};

template<class ElemType>
class Stack:public AbsStack<ElemType>{
	public:
		Stack():top(0){};  //构造函数
		~Stack(){ MakeEmpty();}  //析构函数
		bool IsEmpty() const {return top == 0;}  //判栈空
		bool IsFull() const {return false;}   //判栈满
		void MakeEmpty();     //将栈清空
		void Push( ElemType &x);  //进栈
		void Pop();        //出栈
		const ElemType &Top(); //取顶点元素
		const Stack &operator=(const Stack &R);
	private:
		ListNode<ElemType> *top;             //栈顶指针
};

template<class ElemType>
const ElemType &Stack<ElemType>::Top(){ //读取栈顶结点
	Exception(IsEmpty(), "There is not a node!");
	return top->Element;
}

template<class ElemType>
void Stack<ElemType>::Push( ElemType &x){
	top = new ListNode<ElemType>(x, top);
}

template<class ElemType>
void Stack<ElemType>::Pop(){  //将栈顶元素出栈
	Exception(IsEmpty(), "Stack is underflow!");
	ListNode<ElemType> *q = top;
	top = top->Next;
	delete q;
}

template<class ElemType>
const Stack<ElemType> &Stack<ElemType>::operator=(const Stack<ElemType> &R){
	if(this == &R) return *this;
	MakeEmpty();
	if(R.IsEmpty()) return *this;
	ListNode<ElemType> *p = new ListNode<ElemType>(R.top->Element);
	ListNode<ElemType> *Rp = R.top->Next;
	top = p;
	while(Rp != 0){
		p->Next = new ListNode<ElemType>(Rp->Element);
		p = p->Next;
		Rp = Rp->Next;
	}
	return *this;
}

template<class ElemType>
void Stack<ElemType>::MakeEmpty(){
	while(!IsEmpty()) Pop();
}

void main()
{

}