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copied!<p>It's because you took your List by value- that is, you copied it. You need to take it by const reference- that is,</p> <p><code>ostream &operator<<(ostream &stream, const List& theList)</code></p> <p>Furthermore, your assignment operator should take a const reference, not a non-const ref.</p> <p>I also don't think that this</p> <p><code>delete _head, _tail, _current, _del;</code></p> <p>does what you think it does. It just deletes <code>_del</code> and none of the others.</p> <p>You should use a recursively self-owning design, where each node deletes the next one in the chain. Edit: As this was unclear, I'm going to post a brief sample.</p> <pre><code>template<typename T> struct Node { Node(const T& arg, Node* prev) : t(arg), previous(prev) {} T t; std::auto_ptr<Node<T>> next; Node<T>* previous; }; template<typename T> class List { std::auto_ptr<Node<T>> head; Node<T>* tail; public: List() : head(NULL), tail(NULL) {} void clear() { head = tail = NULL; } // Notice how simple this is void push_back() { push_back(T()); } void push_back(const T& t) { if (tail) { tail = (tail->next = new Node<T>(t, tail)).get(); return; } tail = (head = new Node<T>(t, NULL)).get(); } void pop_back() { tail = tail->previous; tail->next = NULL; } void pop_front() { head = head->next; } List<T>& operator=(const List& ref) { clear(); // Clear the existing list // Copy. Gonna leave this part to you. } }; </code></pre> <p>Notice how I never deleted anything- <code>std::auto_ptr</code> did everything for me, and manipulating the list and it's nodes became much easier, because <code>std::auto_ptr</code> manages all of the memory involved. This list doesn't even need a custom destructor.</p> <p>I suggest that you read up heavily on <code>std::auto_ptr</code>, it has some surprises in it's interface, like the "copy" constructor and assignment operator actually move, that you are going to want to know about before using the class. I wish I could start using <code>std::unique_ptr</code> instead all of the time, which would make life so much easier.</p>

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