List.h

#ifndef LIST_H
#define LIST_H
#include <initializer_list>
#include <string>

class List {
private:
    class Node {
    public:
        Node()=default;
        ~Node()=default;
        Node(int v, Node* p, Node* n);
        Node* prev;
        Node* next;
        int value;
    };
    Node *head;
    Node *tail;
    void deleteList (Node *curr);

public:
    List();
    ~List();
    List(int i);
    List(std::initializer_list<int> l);
    List(List const& rhs);
    List& operator = (List&& rhs);
    List& operator = (List const& rhs);
    void insert (int i);
    void remove (int i);
    int at(unsigned int const index) const;
    int size() const;
    std::string to_string();

    class Smart_Step {
    public:
        Smart_Step()=default;
        ~Smart_Step()=default;
        Smart_Step& operator ++ ();
        bool operator != (int const rhs) const;
        Smart_Step operator = (Smart_Step const& rhs);
        Smart_Step operator * (Smart_Step*);
        Node *pos;
    };

    Smart_Step begin();
    Smart_Step end();

};
#endif