Stack class C ++ implementation

Stack classes written by myself may have few functions or many errors, but at least I tested them correctly ,;

Code:

#include <iostream>using namespace std;template <class T>class node{public:node<T>* next;T val;node():next(NULL),val(){};node(T v):next(NULL),val(v){};};template <class T>class my_stack{public:my_stack();~my_stack();void init_stack();bool is_empty();size_t get_len();    T* get_top();void push(const T& e);    void pop(T& e);void display();private:    node<T>* top;    size_t len;};template <class T>my_stack<T>::my_stack(){   top  = NULL;   len = 0;}template <class T>my_stack<T>::~my_stack(){node<T>* pre = top;if (top){       delete top;   top = pre->next;   pre = pre->next;}len = 0;}template <class T>bool my_stack<T>::is_empty(){return len == 0;}template <class T>size_t my_stack<T>::get_len(){return len;}template <class T>void my_stack<T>::push(const T& e){   node<T>* tmp = new node<T>(e);   if (top == NULL)   {   top =tmp;   }   else   {   tmp->next = top;   top = tmp;   }   ++len;}template <class T>void my_stack<T>::pop(T& e){if(is_empty())throw new exception("The stack is empty!");e = top->val;    if (len ==1)    {top  = NULL;    }else{        node<T>* tmp = top;        top = top->next;delete tmp;}--len;   }template <class T>void my_stack<T>::display(){   node<T>* pre = top;   cout << "The stack is: ";   while(pre)   {   cout << pre->val << " ";   pre = pre->next;   }   cout << endl;}int main(){    my_stack<int> s;s.push(1);s.push(2);s.display();int e = 0;s.pop(e);s.display();cout << e;}