I am trying to implement a queue based on a Linked List that I had to write previously. It is templated and for some reason I am getting the following error using g++ when I compile:

g++ LinkedQueueMain.cpp -o LinkedQueueMain
/tmp/ccqwStpK.o: In function `main':
LinkedQueueMain.cpp:(.text+0x2ee): undefined reference to `LinkedQueue<char>::operator=(LinkedQueue<char> const&)'
collect2: ld returned 1 exit status

It is saying undefined reference however I have declared and defined it so I cant figure out what the problem is.

This is my class declaration and definition:

// LinkedQueue.h

#ifndef LINKEDQUEUE_H
#define LINKEDQUEUE_H

#include <iostream>
#include "RuntimeException.h"
#include "LinkedList.h"

template<typename T> class LinkedQueue;

template<typename T>
std::ostream& operator<<(std::ostream& out, const LinkedQueue<T>& queue);

template<typename T>
class LinkedQueue {
private:
   LinkedList<T> ll;

public:
   // user-defined exceptions
   class QueueEmptyException : public RuntimeException {
   public:
     QueueEmptyException() : RuntimeException("Access to an empty queue") {}
   };

   LinkedQueue() { } // constructor
   ~LinkedQueue() { } // destructor
   LinkedQueue(const LinkedQueue& queue) { ll = queue.ll; } // copy constructor
   LinkedQueue& operator=(const LinkedQueue& queue); // assignment operator
   
   // I have cut out accessory function declarations
   
   friend std::ostream& operator<< <>(std::ostream& out, const LinkedQueue<T>& queue); // overload <<
};

//-------------------------------------------------------------------------------------------------------------------------

template<typename T>
LinkedQueue<T>& LinkedQueue<T>::operator=(const LinkedQueue& queue) {
	ll = queue.ll;
	return *this;
}

// other functions defined here I just cut them out for space

#endif

Here is my main:

#include "LinkedQueue.h"
#include <iostream>
#include <string>
#include <iterator>
using namespace std;

int main()
{
  LinkedQueue<char> queue;
  LinkedQueue<char> queue_copy;

  //===== enqueue() =====
   
  queue.enqueue('1');
  queue.enqueue('2');
  queue.enqueue('3');
  queue.enqueue('4');
  queue.enqueue('5');
  queue.enqueue('6');
   
  queue_copy = queue;  //THIS IS WHERE I BELIEVE THE PROBLEM IS
  cerr << "assigning queue to queue_copy, queue_copy = ";
  cerr << queue_copy << endl;
  cerr << "size of queue_copy = " << queue_copy.size() << endl;
  cerr << "first of queue_copy = " << queue_copy.first() << endl << endl;

return 0;
}

Thanks in advance for any help.

Are you sure this code works:

ll = queue.ll;

'll' is under private section, right? I'm not sure if you can access it.
Here's my code example if it helps:

//operators
//=
Complex& Complex::operator=(Complex const& aCplx){
    if (this != &aCplx){
        mNum.Im = aCplx.getIm();
        mNum.Re = aCplx.getRe();
    }
    return *this;
}
Comments
thanks for trying to help

Our professor gave us a skeleton of the code and it already had the return statement in it so I didn't change it. The LinkedList = operator overload returns a pointer as well.

I am not sure about this , But Why returning (*this)? In your = operator.

(*this) is returned so you can write things like:
myObjA = myObjB = myObjC;

Are you sure this code works:

ll = queue.ll;

'll' is under private section, right? I'm not sure if you can access it.
Here's my code example if it helps:

//operators
//=
Complex& Complex::operator=(Complex const& aCplx){
    if (this != &aCplx){
        mNum.Im = aCplx.getIm();
        mNum.Re = aCplx.getRe();
    }
    return *this;
}

Well the definition is within the class and classes can access their own private data members so ya it should work. I tried putting it in the public section just to check and it did the same thing. As to your example thats basically the same thing that im trying to do. I don't see why mine doesnt work.

Well the definition is within the class and classes can access their own private data members so ya it should work. I tried putting it in the public section just to check and it did the same thing. As to your example thats basically the same thing that im trying to do. I don't see why mine doesnt work.

I'm not sure about this.
Function can access IT'S own members (this->memb1; this->memb2;)
But I'm really not sure about accessing other instance of same type...

Maybe your problem is in something else...

I'm not sure about this.
Function can access IT'S own members (this->memb1; this->memb2;)
But I'm really not sure about accessing other instance of same type...

Maybe your problem is in something else...

I have done something very similar to that previously so I am pretty sure thats not the problem.

BTW Thanks to everyone thats been trying to help. This is getting really frustrating.

I think its zipped now thats the first time I have done that. I am sorry its been so long. I had an emergency that kept me from the computer for a couple days. Im back now and still annoyed by this error.

template<typename T>
LinkedQueue& LinkedQueue::operator=(const LinkedQueue& queue)
{
	ll = queue.ll;
	return *this;
}

You need to be more careful about specifying template parameters:

template<typename T>
LinkedQueue<T>& LinkedQueue<T>::operator=(const LinkedQueue<T>& queue)
{
	ll = queue.ll;
	return *this;
}
Comments
thanks

o crap i must have zipped an older version. I had had that and it still didn't work. I just ended up redoing the entire header and now it works so thank you to everyone who helped

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