Re: template syntax for nested classes - custom iterators

Fei Liu <>
Thu, 03 Apr 2008 18:05:38 -0400
Christopher wrote:

I am trying to implement a generic tree class, as I had mentioned in a
previous post. I want it to be STL like, so I went and researched how
to implement an iterator and copied an example from a page online.

template <class T>
class GenericTree

   class Node
      Node(const T & data) {}

      // other methods

   Node * m_root;


   // Other methods

   class Iterator : std::iterator<std::foward_iterator_tag, T>

      Iterator(Node * node)

      // Other methods

      T * operator -> ()
         return (&*(GenericTree<T>::Iterator)*this);


      Node * m_node;

   Iterator begin()
      return Iterator(m_root);

   // Other methods

When I use it with the following code:

GenericTree<int> tree;
GenericTree<int> Iterator it = tree.begin();
it->() = new int(0);

I get an error:

"expected unqualified-id before '(' token
In member function 'T* GenericTree<T>::Iterator::operator->() [with T
= int]'
Instantiated from here
dependant-name ' GenericTree<T>::Iterator' is a parsed non-type, but
instantiation yields a type
note: say 'typename GenericTree<T>::Iterator' is a type is meant

I assume I need to use the typename keyword somewhere, but am unclear
where. Is my syntax incorrect? Can someone give a correct syntax with
nested template classes?

There is a type mismatch between (&*(GenericTree<T>::Iterator)*this) and
  T *. It'd be helpful if you could post a complete sample code.

Another note is I don't think there is something called


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