C++ Generic Linked List and Iterator - c++

Question

I've just started with learning C++ and I need to write a generic linked list and iterator. This is the code that I wrote (list.h), but I think it is not correct. It does not work and I am not sure that it is generic.
#include <iostream>
#include <cassert>
using namespace std;
using namespace ListExceptions;
class List;
class Iterator;
template<class T>
class Node{
private:
T data;
Node* previous;
Node* next;
friend class List;
friend class Iterator;
public:
Node(T element){
data = element;
previous = NULL;
next = NULL;
}
};
class List{
private:
Node* first;
Node* last;
public:
List(){
first = NULL;
last = NULL;
}
void pushBack(T element);
void insert(Iterator iter, T element);
Iterator remove(Iterator i);
Iterator find(const Predicate& predicate);
void sort(const Compare& comparer);
int getSize() const;
Iterator begin();
Iterator end();
};
class Iterator{
private:
Node* position;
Node* last;
friend class List;
public:
Iterator();
void next();
T getElement()const;
bool equals(Iterator b) const;
bool notEquals(Iterator b) const;
};
If someone can help me?

Answer 1

First thing is that the List and Iterator are non-templated classes, and you probably want to create Lists of a given type. You might consider refactoring the code so that both the Node and the Iterator are internal classes to the List type (it will make things simpler):
template <typename T>
class List {
public:
typedef T value_type;
class Iterator;
struct Node { // Internal to List<T>, so there will be different
// List<T>::Node for each instantiationg type T
// But you don't need the extra <T> parameter for List
// or Iterator
value_type data;
Node* next;
Node* last;
friend class List; // Inside List<T>, List by itself refers to List<T>
friend class Iterator;
};
//...
};
The alternative is a little more complex in code:
template <typename T> class List;
template <typename T> class Iterator;
template <typename T> class Node {
T data;
Node * next;
Node * last;
friend class List<T>;
friend class Iterator<T>;
};
template <typename T>
class List {
Node<T>* first; // note <T> required
//...
};