#include <iostream>



using namespace std;

template<typename T>
class list{
    class cell{
        T elem;
        cell *prev;
        cell *next;
        cell ( T e, cell *p, cell *n): elem(e),prev(p),next(n){};
        friend class list<T>;

    };

    cell *first,*last;
public:
    using iterator=cell*;
    list(){
        last = new cell (T(),nullptr ,nullptr);
        first = last;
    }
    ~list (){
        clear();
        delete first;
    }

    iterator begin(){
        return first;
    }
    iterator end(){
        return last;
    }
    iterator insert (iterator donde,T que){
        cell *anterior= donde->prev;
        cell *aux=new cell(que,donde->prev,donde);
        donde->prev= aux;
        if (anterior) anterior ->next = aux;
        else first = aux;
        return aux;
    }
    iterator erase(iterator cual){



    }
    iterator prev(iterator it){
        return it->prev;
    }
    iterator next(iterator it){
        return it->next;
    }
    T &retrieve(iterator it){

        return it->elem;

    }
    void clear(){
        while(!empty()){
            erase(begin());
        }
    }
    int size();
    bool empty(){
        return begin()==end();
    }




};


int main(int argc, char *argv[]) {

    list <char> L;
    L.insert(L.begin(), 'A');
    L.insert(L.end(),'D');
    list <char>::iterator it=L.begin();
    it=L.next(it);
    L.insert(it,'E');
    for(list<char>::iterator it=L.begin();
    it!=L.end(); it=L.next(it)){
        cout<<L.retrieve(it);
    }
    cin.get();

    return 0;
}