0

I'm learning basic Linked Lists and wanted to try my hand at writing my own implementation. However, I keep getting the following errors when compiling:

/tmp/ccNerPXr.o: In function `main':
main.cpp:(.text+0x10): undefined reference to `LinkedList<int>::LinkedList()'
main.cpp:(.text+0x2c): undefined reference to `LinkedList<int>::insert(int const&)'
main.cpp:(.text+0x49): undefined reference to `LinkedList<int>::displayList()'
collect2: error: ld returned 1 exit status

I've looked at other stack overflow answers and couldn't find one to meet my specific issue. The name of the template class matches the instance declaration in main, I remembered to #include "LinkedList.h" properly, and I double-checked to make sure the forward declarations in *.h matched the ones in *.cpp. What else could be causing this error? Is it staring me in the face, and I'm just too blind to see it? I feel like this might be simpler than what I'm making it...

Here is my (unfinished) source code for reference: main.cpp 

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

int main() 
{ 
    LinkedList<int> normList;
    for(int i = 0; i < 5; i++) 
        normList.insert(i);  

    normList.displayList(); 

    return 0; 
}

LinkedList.h 

#ifndef LINKEDLIST_H
#define LINKEDLIST_H
#include <cstddef>   

template <class Object>
class LinkedList  
{ 
    struct ListNode
    { 
        Object element; 
        ListNode *next;
        ListNode() : element(0), next(NULL) {};      
    }; 

        ListNode *head; 
        ListNode *tail; 

    public: 
        LinkedList();   
        void insert(const Object &x); 
        void erase(const Object &x); 
        void eraseList(); 
        void displayList(); 

}; 

#endif

LinkedList.cpp 

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

template <class Object>
LinkedList<Object>::LinkedList()
{ 
    head = NULL; 
}   

/*This function will insert an object
*using the tail-end insertion method
*i.e., inserting at the end of the list  
*/

template <class Object>
void LinkedList<Object>::insert(const Object &x) 
{
    ListNode *newNode = new ListNode(x, NULL); 

    if( !head ) {  
       head = newNode;
       tail = head;  
    } else {  
       tail->next = newNode; 
       tail = newNode;          
    } 

}//insert() 

template <class Object>
void LinkedList<Object>::erase(const Object &x) 
{ 
    ListNode *prev; 


} //erase()

/*
*Function that deletes entire list 
*/ 
template <class Object> 
void LinkedList<Object>::eraseList() 
{ 
    ListNode *prev;
    while(head->next) 
    {   
        prev = head; 
        delete head; 
        head = prev->next; 
    } 

}//eraseList()

template <class Object> 
void LinkedList<Object>::displayList() 
{ 
    if(!head) 
        cout << "The list is empty\n"; 

    while(head->next) 
    { 
        cout << head->element << endl; 
        head = head->next; 
    }   

} //displayList()

Thanks in advance to any help or input

FunkyFrap
  • 1

0 Answers0