Question

EDIT — Answered below, missed the angled braces. Thanks all.

I have been attempting to write a rudimentary singly linked list, which I can use in other programs. I wish it to be able to work with built-in and user defined types, meaning it must be templated.

Due to this my node must also be templated, as I do not know the information it is going to store. I have written a node class as follows –

template <class T> class Node
{
    T data; //the object information
    Node* next; //pointer to the next node element

public:
    //Methods omitted for brevity
};

My linked list class is implemented in a seperate class, and needs to instantiate a node when adding new nodes to the end of the list. I have implemented this as follows –

#include <iostream>
#include "Node.h"
using namespace std;

template <class T> class CustomLinkedList
{
    Node<T> *head, *tail;

public:

    CustomLinkedList()
    {
        head = NULL;
        tail = NULL;
    }

    ~CustomLinkedList()
    {

    }

    //Method adds info to the end of the list
    void add(T info)
    {
        if(head == NULL) //if our list is currently empty
        {
            head = new Node<T>; //Create new node of type T
            head->setData(info);
            tail = head;
        }
        else //if not empty add to the end and move the tail
        {
            Node* temp = new Node<T>;
            temp->setData(info);
            temp->setNextNull();
            tail->setNext(temp);
            tail = tail->getNext();
        }
    }

    //print method omitted
};

I have set up a driver/test class as follows –

#include "CustomLinkedList.h"
using namespace std;

int main()
{
    CustomLinkedList<int> firstList;

    firstList.add(32);
    firstList.printlist();
    //Pause the program until input is received
    int i;
    cin >> i;

    return 0;
}

I get an error upon compilation however – error C2955: ‘Node’ : use of class template requires template argument list – which points me to the following line of code in my add method –

Node* temp = new Node<T>;

I do not understand why this has no information about the type, since it was passed to linked list when created in my driver class. What should I be doing to pass the type information to Node?

Should I create a private node struct instead of a seperate class, and combine the methods of both classes in one file? I’m not certain this would overcome the problem, but I think it might. I would rather have seperate classes if possible though.

Thanks, Andrew.

Answer 1

Might wanna try

Node<T>* temp = new Node<T>;

Also, to get hints on how to design the list, you can of course look at std::list, although it can be a bit daunting at times.