stack.h

模拟计算器的实现

#include<assert.h>
template<class type> class stack;
template<class type> class stacknode{
	friend class stack<type>;
	private:
		type data;
		stacknode<type>* link;
		stacknode(type d=0,stacknode<type>* l=NULL): data(d),link(t){}
};

template<class type>class stack{
	public:
		stack():top(NULL){}
		~stack();
		void push(const type& item);
		type pop();
		type gettop();
		void makeempty();
		int isempty()const{ return top=NULL;}
	private:
		stacknode<type>* top;
};

template<class type>stack<type>::~stack(){
	stacknode<type>* p;
	while(top!=NULL){p=top;top=top->link; delete p;}
}
//往栈顶插入元素
template<class type>stack<type>::push(const type& item){
	stacknode<type>* p=top;
	top=new stacknode<type>(item,p);
}//这个压入函数是自己改过的

//删除栈顶元素
template<class type>type stack<type>::pop(){
	assert(!isempty());
		stacknode<type>* p=top;
		type revalue=p->data;  top=top->link;
		delete p; return revalue;
}

template<class type>type stack<type>::gettop(){
	assert(!isempty());
	return top->data;
}