stack.h

计算器程序

//****************************************************************
//This software may not be distributed further without permission from
// Sun Xueshi's Group
//      
//This software is distributed WITHOUT ANY WARRANTY. No claims are made
// as to its functionality or purpose.
// 
//Authors: 孙学诗，孙海洋
// Date: 12/4/03
// 
//****************************************************************

#include<iostream>
#include<cassert>

using namespace std;

template <class Type>class Stack;

template <class Type>class StackNode{
 	friend class Stack<Type>;
       public:
 	       StackNode(Type d = 0,StackNode<Type> *l = NULL)
 		     : data(d), link(l) {}
 	private:
 		Type data;
 		StackNode<Type> *link;
};  

template <class Type>class Stack {
	public:
		Stack() : top(NULL){}
	       ~Stack();
	       int Push(const Type &item);
	       Type Pop();
	       Type GetTop();
	       void MakeEmpty() {top = NULL;}
	       int IsEmpty() const { return top == NULL; }  //if stack is empty, return ture
	private:
		StackNode<Type> *top;
};
//Destroy stack
template<class Type> 
Stack<Type>::~Stack(){
	StackNode<Type> *p;
	while( top != NULL ){
		p = top;
		top = top->link;
		delete p;
	}
}
//Push a value into stack
template<class Type>
int Stack<Type>::Push(const Type &item){
	top = new StackNode<Type>(item,top);
       return 1;
}
//get a value from stack and delete it from stack
template<class Type>
Type Stack<Type>::Pop(){
       Type value;
       if( !IsEmpty() ) {
        	StackNode<Type> *p = top;
                value = p ->data;
                top = top->link;
               delete p;
       	}
       else value = 0;   //if stack is empty return 0
       return value;
}
//Get a value from top of stack
template<class Type>
Type Stack<Type>::GetTop(){
        Type Value;
	if( !IsEmpty() )
		Value = top->data;
	else Value = 0;       //if stack is empty return 0
	return Value;
}