Адаптация контейнера под STL

template <typename Elem> 
struct Link {
    Elem data;
    Link* next;
 
    Link(const Elem d) {
        data = d;
        next = nullptr;
    }
 
    Link() {
        data = Elem();
        next = nullptr;
    }
};
 
template <typename T>
class slist {
public:
    class iterator;
    slist() { 
        head = curr = tail = new Link<T>(); 
        size = 0;
    }
    
    slist(const T data) { 
        head = curr = tail = new Link<T>(data); 
        size = 1;
    }
    
    ~slist();
 
    void push_back(T data);
    
    int get_size() {
        return size;
    }
    
    iterator begin() { return iterator(head); }
    iterator end() { return iterator(tail); }
 
private: 
    int size;
    Link<T>* head;
    Link<T>* tail;
    Link<T>* curr;
};
 
template <typename T> class slist<T>::iterator {
private:
    friend class slist;
    Link<T>* current;
public:
    iterator() : current(curr) {}
    iterator(Link<T>* data) noexcept : current(data) {}
 
    iterator& operator++() {
        if (current) current = current->next;
        return *this;
    }
    
    T& operator*() { return current->data; }
};
 
template <typename T>
void slist<T>::push_back(T data) {
    Link<T>* nLink = new Link<T>(data);
    if (size == 0) {
        head->data = data;
        curr->data = data;
        size = 1;
    }
    else {
        while (curr->next) curr = curr->next;
        curr->next = nLink;
        tail = curr;
        size++;
    }
}
template <typename T>
slist<T>::~slist (){
    while (curr) {
        Link<T> *tmp = curr;
        curr = curr->next;
        delete tmp;
    }
    delete head;
}