Question

I’m trying to create my own templated List class as a practice excercise. I should have probably started smaller but there you go.. i’m getting the error “expected unqualified-id before ‘<‘ token ” at each line that reads:

typedef <typename ListType>

I’m a student and I’ve been reading up on templates for a couple of hours but still cant figure this one out, any help would be much appreciated!

My hpp file for List:

#if !defined _LIST_HPP_
#define _LIST_HPP_

#include "Node.hpp"

///since we're creating a template everything must be defined in the hpp

typedef <typename ListType>
class List
{
   public:
      List();
      bool Empty();
      void PushFront();
      void PushBack();
      void PopBack();
      Node<ListType>& GetHead();

   private:
      int _size;
      Node<ListType>* _head;
      Node<ListType>* _tail;
};


///implement List class here
typedef <typename ListType>
List<ListType>::List() : _head(0), _tail(0), _size(0)
{
}
typedef <typename ListType>
bool <ListType>Empty()
{
   return !_size; //returns true if size = 0
}
typedef <typename ListType>
void List<ListType>::PushFront()
{
   _head = new Node<ListType>( _head , 0 );
   if (!Empty())
      _head->_prev->_next = _head; //set previous nodes _next to new _head

   ++_size;
}
typedef <typename ListType>
void List<ListType>::PushBack()
{
   _tail = new Node<ListType>( 0 , _tail);
   if (!Empty())
      _tail->_next->_prev = _tail; // set old tails _prev to new tail

   ++_size;
}
typedef <typename ListType>
void List<ListType>::PopBack()
{

}
typedef <typename ListType>
Node<ListType>& List<ListType>::GetHead()
{
   return _head;
}

#endif //define

And i’ll also include the templated node class hpp incase it could be something there that’s throwing things off?

#if !defined _NODE_HPP_
#define _NODE_HPP_


//#include "Sprite.hpp"

template<typename NodeType>
class Node{
   public:
      Node( Node* prev = 0, Node* next = 0);
      void SetData(NodeType newData);
      void GetData();
   private:
      friend class List;

      NodeType _data;
      Node* _next;
      Node* _prev;

};


///implement Node

template <typename NodeType>
Node<NodeType>::Node(Node* prev, Node* next) : _prev(prev), _next(next)
{}
template <typename NodeType>
void Node<NodeType>::SetData(NodeType newData)
{
   _data = newData;
}
template <typename NodeType>
void Node<NodeType>::GetData()
{
   return _data;
}

#endif //define

Answer 1

It’s template, not typedef.

And while we’re at it, your preprocessor tokens are invalid identifiers since they start with an underscore, which isn’t allowed here. Use something like LIST_HPP instead.

Finally, let’s take a look at your Empty definition:

typedef <typename ListType>
bool <ListType>Empty()
{
   return !_size; //returns true if size = 0
}

First of all, this is missing the class name in the method name. Secondly, I dislike the conversion from a number to bool. Why not use an explicit comparison? That also obviates the comment, which is useless in itself since it merely paraphrases the code.

This leaves us with:

template <typename ListType>
bool List<ListType>::Empty()
{
    return _size != 0;
}