I am trying to implement a Circular Doubly Linked List, and I have no probably with the Linked List implementation itself. The problem I am having is allowing it to take generic parameters using templates. I have checked several tutorials dealing with templates, but I haven't found anything specific to what I am trying to do.
I believe I have worked out most of the errors, but I am still getting the errors:
linkedlist.h(37): error C2955: 'Node' : use of class template requires template argument list
linkedlist.h(9) : see declaration of 'Node'
main.cpp(6) : see reference to class template instantiation 'LinkedList<T>' being compiled
with
[
T=int
]
Here is my code:
LinkedList.h:
#ifndef LINKEDLIST_H
#define LINKEDLIST_H
#include <iostream>
//node
template <class T>
class Node
{
private:
public:
bool first; //boolean tag
Node * next; //pointer to the next node
Node * prev; //pointer to the prev node
T data; //placeholder for generic data
Node(T d); //constructor
};
template <class T>
Node<T>::Node(T d)
{
next = NULL;
prev = NULL;
data = d;
first = false;
}
//a circular doubly-linked list
template <class T>
class LinkedList
{
private:
public:
Node * p; //reference to the current node
LinkedList(); //constructor
bool empty(); //returns true if the list is empty, false otherwise
int size(); //returns the number of elements in the list
void insertBefore(T d); //inserts a node before the current node
void insertAfter(T d); //inserts a node after the current node
void remove(); //removes the current node
void moveAhead(); //moves to the next node
void moveBack(); //moves to the previous node
T access(); //returns the data of the current node
void listContents(); //displays the data of every element in the list starting with the current
};
template <class T>
LinkedList<T>::LinkedList()
{
p = NULL;
}
template <class T>
bool LinkedList<T>::empty()
{
if (p == NULL)
{
std::cout << "List is Empty.\n";
return true;
}
else
return false;
}
template <class T>
int LinkedList<T>::size()
{
if (p == NULL)
{
return 0;
}
if (p->next == p)
{
return 1;
}
else
return 2; //placeholder
}
template <class T>
void LinkedList<T>::insertBefore(T d)
{
Node *q, *t;
if (p == NULL)
{
p = new Node<T>(d);
p->next = p;
p->prev = p;
//std::cout << d << " inserted.\n";
}
else
{
if (p-> next == p)
{
q = new Node<T>(d);
q->next = p;
q->prev = p;
p->next = q;
p->prev = q;
//std::cout << d << " inserted.\n";
}
else
{
q = p->prev;
t = new Node<T>(d);
p->prev = t;
q->next = t;
t->next = p;
t->prev = q;
//std::cout << d << " inserted.\n";
}
}
}
template <class T>
void LinkedList<T>::insertAfter(T d)
{
Node *q, *t;
if (p == NULL)
{
p = new Node<T>(d);
p->next = p;
p->prev = p;
//std::cout << d << " inserted.\n";
}
else
{
if (p-> next == p)
{
q = new Node<T>(d);
q->next = p;
q->prev = p;
p->next = q;
p->prev = q;
//std::cout << d << " inserted.\n";
}
else
{
q = p->next;
t = new Node<T>(d);
p->next = t;
q->prev = t;
t->next = q;
t->prev = p;
//std::cout << d << " inserted.\n";
}
}
}
template <class T>
T LinkedList<T>::access()
{
if (p == NULL)
{
std::cout << "The list is empty. No data to be accessed.\n";
return NULL;
}
else
return p->data;
}
template <class T>
void LinkedList<T>::remove()
{
if (p == NULL)
std::cout << "The list is empty. No node exists to be removed.\n";
}
template <class T>
void LinkedList<T>::moveAhead()
{
p = p->next;
}
template <class T>
void LinkedList<T>::moveBack()
{
p = p->prev;
}
template <class T>
void LinkedList<T>::listContents()
{
if (p == NULL)
{
std::cout << "This list is empty, there are no elements to be displayed.";
}
else
{
Node *q;
p->first = true;;
q = p;
while (!q->next->first)
{
//std::cout << q->data << ", ";
q = q->next;
}
//std::cout << q->data << ".\n";
p->first = false;
}
}
#endif
main.cpp:
#include <iostream>
#include "LinkedList.h"
int main()
{
LinkedList<int> list;
list.empty();
std::cout << "p list size is: " << list.size() << std::endl;
list.remove();
list.access();
list.insertBefore(3);
list.insertBefore(2);
list.moveBack();
list.insertBefore(1);
list.moveBack();
list.moveAhead();
list.moveAhead();
list.insertAfter(5);
list.insertAfter(4);
list.moveBack();
list.moveBack();
list.listContents();
system("PAUSE");
return 0;
}
As far as I'm aware I haven't done much wrong, I just need to correct those few errors. If I have done something majorly wrong if you could please point it out to me, or direct me to an appropriate resource it would be much appreciated.
Thanks in advance.
