linked list template class doesn't compile

**weaknessforcats** · Nov 13 '09, 05:40 PM

Which textbook are you using?

There are so mnay errors in this example I can't believe it's in a book.

**QiongZ** · Nov 13 '09, 06:33 PM

C++ How to program by Deitel and Deitel.

What kind of errors? Can you point out some of them for me? Thank you for your reply.

One thing to note again: if I remove all the templates, the program compiled successfully.

Qiong

**weaknessforcats** · Nov 13 '09, 07:03 PM

I found the example. The Deitel book I have is dated 1994. That's before templates were actually working in C++.

Further, you don't write linked lists in C++. Instead you use the C++ Standard Library list template.

This book is so old that there was no C++ Standard Library. It didn't appear until 1998.

In fact, all C++ books prior to September 1998 are pre-ANSI C++ and should be discarded.

Get a newer book.

In ANSI C++ a template is a pattern. When you specialize the template, the compiler makes a copy of it and replaces the typename placeholder with the actual type.

Since the compiler needs to have the template in order ot make a copy, the template is a declaration and therefore all templates are placed in header files.

The specializations are placed in the .cpp files.

All this being said, it appears the example was not copied exactly into your computer. Like a typename of T appears whereas in the example everything is typename NODETYPE.

I would make sure that all the temp[lates are in .h files. The only .cpp file you should have is the Driver.cpp file.

Finally is appears your Visual Studio project is not set up correctly. You have a Windows console program and you really want a Console program without the Windows stuff.

Do this:

1) Create a Win32 application.
2) When trhe wizard appears, DO NOT CLICK FINISH.
3) Instead, click application settings.
4) Select a) empty project and b) console application
5) Now click FINISH.

Post again if you are still stuck.

**QiongZ** · Nov 13 '09, 07:58 PM

Thank you very much for your reply. I made a few changes you suggested. I put templates all in header files and I am listing them again so that it is easy to see on which lines the errors occurred.

linked-list-driver.cpp

Code:

// linked-list-driver.cpp : Defines the entry point for the console application.
//

//#include "stdafx.h"
#include <iostream>
#include "list1.h"

using std::cout;
using std::cin;
using std::endl;

void testIntegerList();
void instructions();

main()
{
	testIntegerList();
	return 0;
}

void testIntegerList()
{
	cout << "Testing a List of integer values" << endl;

	List1<int> integerList;

	instructions();

	int choice, value;

	do {
		cout << "? ";

		cin >> choice;

		switch (choice) {

			case 1:
				cout << "Enter an integer: ";
				cin >> value;
				integerList.insertAtFront(value);
				integerList.print();
				break;

			case 2:
				cout << "Enter an integer: ";
				cin >> value;
				integerList.insertAtBack(value);
				integerList.print();
				break;

			case 3:
				if (integerList.removeFromFront(value))
					cout << "integer removed from front" << endl;
				integerList.print();
				break;

			case 4:
				if (integerList.removeFromBack(value))
					cout << "integer removed from back" << endl;

				integerList.print();
				break;

		}
	} while (choice != 5);

	cout << "End test of integer list" << endl;
}

void instructions()
{
	cout << "Enter one of the following:" << endl
		<< " 1 to insert at beginning of list" << endl
		<< " 2 to insert at the end of list" << endl
		<< " 3 to delete from beginning of list" << endl
		<< " 4 to delete from end of list" << endl
		<< " 5 to end list processing" << endl;
}

list1.h

Code:

#ifndef LIST1_H
#define LIST1_H

//#include "stdafx.h"
#include "listnd.h"
#include <iostream>
#include <assert.h>
using std::cout;
using std::endl;

template<class T>
class List1 {
public:
	List1();
	~List1();
	void insertAtFront(T &);
	void insertAtBack(T &);
	int removeFromFront(T &);
	int removeFromBack(T &);
	int isEmpty();
	void print();
private:
	ListNode<T> *firstPtr;
	ListNode<T> *lastPtr;
	ListNode<T> *getNewNode(T &);
};

template<typename T>
List1<T>::List1() {firstPtr = lastPtr = 0;}

template<typename T>
List1<T>::~List1()
{
	if (!isEmpty()) {
		cout << "Destroying nodes ... " << endl;

		ListNode<NODETYPE> *currentPtr = firstPtr, *tempPtr;
		while (currentPtr != 0) {
			tempPtr = currentPtr;
			cout << tempPtr->data << endl;
			currentPtr = currentPtr->nextPtr;
			delete tempPtr;
		}
	}

		cout << "All nodes destroyed" << endl << endl;
}

template<typename T>
void List1<T>::insertAtFront(T &value)
{
	ListNode<NODETYPE> *newPtr = getNewNode(value);

	newPtr->nextPtr = firstPtr;
	firstPtr = newPtr;
}

template<typename T>
void List1<T>::insertAtBack(T &value)
{
	ListNode<NODETYPE> *newPtr = getNewNode(value);

	lastPtr->nextPtr = newPtr;
	//newPtr->nextPtr = 0;
	lastPtr = newPtr;
}

template<typename T>
int List1<T>::removeFromFront(T &value)
{
	if (isEmpty())
		return 0;
	else {
		ListNode<NODETYPE> *tempPtr = firstPtr;
		if (firstPtr == lastPtr)
			firstPtr = lastPtr = 0;
		else
			firstPtr = firstPtr->nextPtr;

		value = tempPtr->data;
		delete tempPtr;
		return 1;
	}
}

template<typename T>
int List1<T>::removeFromBack(T &value)
{
	if (isEmpty())
		return 0;
	else {
		ListNode<NODETYPE> *tempPtr = lastPtr;
		if (firstPtr == lastPtr)
			firstPtr = lastPtr = 0;
		else {
			ListNode<NODETYPE> *currentPtr = firstPtr;
			while (currentPtr->nextPtr != lastPtr)
				currentPtr = currentPtr->nextPtr;

			lastPtr = currentPtr;
			currentPtr->nextPtr = 0;
		}

		value = tempPtr-data;
		delete tempPtr;
		return 1;
	}
}

template<typename T>
int List1<T>::isEmpty() {return firstPtr == 0;}

template<typename T>
ListNode<NODETYPE> *List1<T>::getNewNode(T value)
{
	ListNode<NODETYPE> *ptr = new ListNode<NODETYPE>(value);

	assert(ptr != 0);
	return ptr;
}

template<typename T>
void List1<T>::print()
{
	if (isEmpty()) {
		cout << "The list is empty" << endl << endl;
		return;
	}

	ListNode<NODETYPE> *currentPtr = firstPtr;

	cout << "The list is: ";

	while (currentPtr != 0) {
		cout << currentPtr->data << ' ';
		currentPtr = currentPtr->nextPtr;
	}

	cout << endl << endl;
}

#endif

listnd.h

Code:

#ifndef LISTND_H
#define LISTND_H

//#include "stdafx.h"

template<typename NODETYPE>
class ListNode {
	friend class List1<T>;
	public: 
		ListNode(NODETYPE &);
		~ListNode();
		NODETYPE getData();
	private: 
		NODETYPE data;			
		ListNode *nextPtr;
};

template<typename NODETYPE>
ListNode<NODETYPE>::ListNode(NODETYPE &info)
{
	data = info;
	nextPtr = 0;
}

template<typename NODETYPE>
NODETYPE ListNode<NODETYPE>::getData() {return data;}

#endif

I got fewer errors this time:

listnd.h(8) : error C2059: syntax error : '<'
listnd.h(16) : see reference to class template instantiation 'ListNode<NODET YPE>' being compiled
listnd.h(8) : error C2238: unexpected token(s) preceding ';'
list1.h(26) : error C2989: 'List1' : class template has already been declared as a non-class template
listnd.h(8) : see declaration of 'List1'
list1.h(11) : error C3857: 'List1': multiple template parameter lists are not allowed
list1.h(29) : error C2988: unrecognizable template declaration/definition
list1.h(29) : error C2059: syntax error : '<'
list1.h(32) : error C2588: '::~List1' : illegal global destructor
list1.h(32) : fatal error C1903: unable to recover from previous error(s); stopping compilation

Qiong

**weaknessforcats** · Nov 13 '09, 08:08 PM

This cose os your first error:

Code:

 friend class List1<T>;

I suggest you research bound vs. unbound friends in templates.

The C++ Primer Plus 5th edition has a good explanantion. And there is Google.

**QiongZ** · Nov 13 '09, 08:42 PM

The problem is solved. Someone suggested me to add

Code:

template< typename T > class List1;

in listnd.h before declaration of ListNode.

And also I did the following two things:

1 took destructor ~ListNode() out of listnd.h
2. make sure all the typename (for class List1 and class ListNode) same

that did the trick.

Thank you very much for your help, weaknessforcats . Hope this post can help someone else in the future.

Qiong

**wysiswyg** · Apr 10 '10, 03:10 AM

Hello

Hi Qiong,

Can you give me the correct code, using your program I am still getting the following errors at compile time.

linked-list-driver.cpp
c:\program files\microsoft visual studio 8\vc\list1.h(11 4) : error C2065: 'NODET
YPE' : undeclared identifier
c:\program files\microsoft visual studio 8\vc\list1.h(12 0) : error C2244: 'List1
<T>::getNewNode ' : unable to match function definition to an existing declaratio
n
c:\program files\microsoft visual studio 8\vc\list1.h(25 ) : see declarat
ion of 'List1<T>::getN ewNode'
definition
'ListNode *List1<T>::getN ewNode(T)'
existing declarations
'ListNode<NODET YPE> *List1<T>::getN ewNode(T &)'

linked list template class doesn't compile

linked list template class doesn't compile

Comment

Comment

Comment

Comment

Comment

Comment

Comment