単一チェーンテーブルでstackを実現

#include <iostream>

using namespace std;
struct node{
        double var;
        node *parent;
        node(){}
};

class stack{
        private :
                int num;
                node *front;
        public:
                stack(){
                        num = 0;
                        front = NULL;
                }
                void push(double v){
                        node * tmp = new node();
                        tmp->var = v;
                        tmp->parent = front;
                        front = tmp;
                        num ++;
                }
                double top(){
                        if(num==0){
                                cout << "no element!" << endl;
                                return 0;
                        }
                        return front->var;
                }
                double pop(){
                        if(num==0){
                                cout << "pop from empty stack!" << endl;
                                return 0;
                        }
                        double s = front->var;
                        node* tmp = front;
                        front = front->parent;
                        delete tmp;
                        num--;
                        return s;
                }
                ~stack(){
                        while( num!=0){
                                cout << "pop: "<< pop() << endl;
                        }
                }
};

int main(){
        stack s;
        for(int i=0;i<10;i++){
                s.push(i);
        }
        for(int i=1;i<5;i++){
                        s.pop();
        }
        cout <<s.top() << endl;
}