Unable to write the same Java code in C++ because "cannot initialize class member here" ERROR

Question

I'm doing a C++ implementation of Singly Linked List that I've already done in Java. The Fraction of my Java code is as follows :

class Node
{
    int info;
    Node next;
    Node()
    {
        next=null;
    }
} 
class Op
{
    Node front= null;

    void display()
    {
        Node rear=front;
        if(rear==null)
            System.out.println("List is empty");
        else
        {
            while(rear!=null)
            {
                System.out.print("["+rear.info+"|"+rear.next+"]"+"--->");
                rear=rear.next;

            }
            System.out.println();
        }
    }
}

next stores the address of the next Node in the list,
front points to the first node in the list and
rear is used to sequentially travel the list.

Below is the C++ code that I'm trying to implement :

class Node
{
    public:
    int info;
    Node *next;
    Node()
    {
        next = NULL;
    }
};
class Op
{
    public:
    Node *front = NULL; //error line.
};

int main()
{
    return 0;
}

I'm using the Turbo C++ 3.0 compiler and the error it gives is :

Cannot initialize a class member here

I'm aware that the above problem can be resolved if I use C++11 but unfortunately the code has to be in Turbo C++ 3.0. The front has to be NULL in order to check if the list id empty or not. How do I solve this issue?

See [this question about initializations in C++](http://stackoverflow.com/q/15451840/4125191). — RealSkeptic, Nov 30 '14 at 18:22

score 1 · Answer 1 · edited Nov 30 '14 at 18:44

1

try this :-

Class Op 
{
 public : Node *front;
 Op():front(NULL){};
};

void main()
{
    Op o  // constructor called.
    Op *op; // pointer - no constructor called.
    Op *op2 = new Op; // constructor called.

    cout << o.front; // NULL
    cout << op->front; // garbage value
    cout << op2->front; // NULL
}

edited Nov 30 '14 at 18:44

egur

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answered Nov 30 '14 at 18:34

3Demon

550
3
9

I tried this inside main(): Op *op; cout<front; – Siddharth Thevaril Nov 30 '14 at 18:36
and that returned an address instead of null, how do I check if it is null inside the if() condition? – Siddharth Thevaril Nov 30 '14 at 18:37
I copy-pasted your code and the output for all the three cout statements are : 0x8f850000 – Siddharth Thevaril Nov 30 '14 at 18:53
The garbage value and the null values are same? – Siddharth Thevaril Nov 30 '14 at 18:54

score 0 · Answer 2 · answered Nov 30 '14 at 18:19

0

have you call the header files? Sometimes JAVA programmer forget to include the header files in C++. :-P

I think the line :-

public * front = NULL;

should be :-

public : NODE *front = NULL;

answered Nov 30 '14 at 18:19

3Demon

550
3
9

That was a typo, my bad. That isn't the issue – Siddharth Thevaril Nov 30 '14 at 18:21
Yes I've called all the header files needed – Siddharth Thevaril Nov 30 '14 at 18:31

score 0 · Answer 3 · answered Nov 30 '14 at 18:20

0

Here's one way to do it in C++:

class Op
{
public:
    Node *front;
    Op() : front(NULL) {}  // default constructor
};

answered Nov 30 '14 at 18:20

egur

7,830
2
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I tried accessing **front** inside main() and it displayed an address. Is this supposed to return an address instead of a NULL value? – Siddharth Thevaril Nov 30 '14 at 18:35
If the list is empty, then **front** must contain **NULL** but instead it has some address inside it. The **if()** condition will fail right? – Siddharth Thevaril Nov 30 '14 at 18:38

score 0 · Answer 4 · answered Nov 30 '14 at 18:28

0

Initialize it in constructor:

Op() :
 front(NULL);
{}

Still it's interesting that it's not working in Turbo C++. g++ can handle it.

answered Nov 30 '14 at 18:28

Michal Špondr

1,337
2
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Unable to write the same Java code in C++ because "cannot initialize class member here" ERROR

4 Answers4