linked list template class doesn't compile

[QiongZ]

Hi, I just recently started studying C++ and basically copied an example in the textbook into VS2008, but it doesn't compile. I tried to modify the code by eliminating all the templates then it compiled no problem. But I can't find the what the problem is with templates? Please help. The main is in test-linked-list.cpp. There are two template classes. One is List1, the other one is ListNode. The codes are below:


// test-linked-list.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();

int _tmain(int argc, _TCHAR* argv[])
{
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
#ifndef LIST1_H
#define LIST1_H

#include "listnd.h"


template<typename 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 &);
};


#endif

// list1.cpp
#include "stdafx.h"
#include "list1.h"
#include <iostream>
#include <assert.h>
using std::cout;
using std::endl;

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;
}


// listnd.h
#ifndef LISTND_H
#define LISTND_H

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

#endif


// listnd.cpp
#include "stdafx.h"
#include "listnd.h"

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

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

I get errors like the following:


Compiling...
list1.cpp
listnd.h(6) : error C2059: syntax error : '<'
listnd.h(14) : see reference to class template instantiation 'ListNode<NODETYPE>' being compiled
listnd.h(6) : error C2238: unexpected token(s) preceding ';'
list1.h(22) : error C2989: 'List1' : class template has already been declared as a non-class template
listnd.h(6) : see declaration of 'List1'
list1.h(7) : error C3857: 'List1': multiple template parameter lists are not allowed
list1.cpp(9) : error C2988: unrecognizable template declaration/definition
list1.cpp(9) : error C2059: syntax error : '<'
list1.cpp(12) : error C2588: '::~List1' : illegal global destructor
list1.cpp(12) : fatal error C1903: unable to recover from previous error(s); stopping compilation
listnd.cpp
listnd.h(6) : error C2059: syntax error : '<'
listnd.h(14) : see reference to class template instantiation 'ListNode<NODETYPE>' being compiled
listnd.h(6) : error C2238: unexpected token(s) preceding ';'
test-linked-list.cpp
listnd.h(6) : error C2059: syntax error : '<'
listnd.h(14) : see reference to class template instantiation 'ListNode<NODETYPE>' being compiled
listnd.h(6) : error C2238: unexpected token(s) preceding ';'
list1.h(22) : error C2989: 'List1' : class template has already been declared as a non-class template
listnd.h(6) : see declaration of 'List1'
list1.h(7) : error C3857: 'List1': multiple template parameter lists are not allowed
test-linked-list.cpp(25) : error C2143: syntax error : missing ';' before '<'
test-linked-list.cpp(25) : error C2143: syntax error : missing ';' before '<'
test-linked-list.cpp(41) : error C2065: 'integerList' : undeclared identifier
test-linked-list.cpp(41) : error C2228: left of '.insertAtFront' must have class/struct/union
type is ''unknown-type''
test-linked-list.cpp(42) : error C2065: 'integerList' : undeclared identifier
test-linked-list.cpp(42) : error C2228: left of '.print' must have class/struct/union
type is ''unknown-type''
test-linked-list.cpp(48) : error C2065: 'integerList' : undeclared identifier
test-linked-list.cpp(48) : error C2228: left of '.insertAtBack' must have class/struct/union
type is ''unknown-type''
test-linked-list.cpp(49) : error C2065: 'integerList' : undeclared identifier
test-linked-list.cpp(49) : error C2228: left of '.print' must have class/struct/union
type is ''unknown-type''
test-linked-list.cpp(53) : error C2065: 'integerList' : undeclared identifier
test-linked-list.cpp(53) : error C2228: left of '.removeFromFront' must have class/struct/union
type is ''unknown-type''
test-linked-list.cpp(55) : error C2065: 'integerList' : undeclared identifier
test-linked-list.cpp(55) : error C2228: left of '.print' must have class/struct/union
type is ''unknown-type''
test-linked-list.cpp(59) : error C2065: 'integerList' : undeclared identifier
test-linked-list.cpp(59) : error C2228: left of '.removeFromBack' must have class/struct/union
type is ''unknown-type''
test-linked-list.cpp(62) : error C2065: 'integerList' : undeclared identifier
test-linked-list.cpp(62) : error C2228: left of '.print' must have class/struct/union
type is ''unknown-type''


Thank you for taking time to look at this. I have been looking at this for a couple days now and really need some help here. Thank you!

Qiong

[kbw]

Can you post the listing of

listnd.h

[QiongZ]

I apologize. My posting is misleading. To clarify, it is not just test-linked-list.cpp up there. The code I posted above includes test-linked-list.cpp, list1.h, list1.cpp, listnd.h, listnd.cpp.

Thank you for your reply.

Qiong

// listnd.h
#ifndef LISTND_H
#define LISTND_H

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

#endif 

[kbw]

Do you need friend class List1<T>;? I'd remove it.

[QiongZ]

I will keep that since class List1 needs to access data member of class ListNode sometimes.

Any other suggestions?

One thing to note again: if I remove all the templates, the program compiled successfully. Could it be something wrong with the template declaration? Everything looks all right with header files includes?

Any pointer is appreciated.

Qiong

[jsmith]

List1<T> is not declared in listnd.h, and the friend declaration only declares friendship,
it does not act as a forward declaration.

listnd.h should have

template< typename T > class List1<T>;

as a forward declaration before the declaration of ListNode.

[QiongZ]

Thank you jsmith. That did the trick! Also thank you kbw for pointing to the right direction.

I also 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

Hope someone can find this post helpful in the future.

Qiong