Re: Simple List Access by Index

Ulrich Eckhardt <>
Sat, 6 Dec 2008 15:05:35 CST
<> wrote:

I've created these simple Node and List classes, but I want to be able
to do something like this: L[0] = 5; L[1] = 10; L[2] = 20; etc.... How
would I need to overload my operator= in the List class?

Actually, my first guess would be that you need to overload operator[], but
let's look at the code...

class Node
     friend ostream& operator<<(ostream& out, const Node& N)
         cout << << " --> ";

Note: you don't have to make this function a friend, there is a public API
to retrieve the value. However, you need to learn about const and non-const
memberfunctions, because as it is now, you can't use getData() on N above,
because getData() is declared as a non-const memberfunction.

     int data;
     Node* next;

     Node() {}
     Node(int d, Node* n)
         data=d; next=n;
     ~Node() {}
     void setData(int d) { data=d; }
     int getData() { return data; }
     void printData() { cout << data << endl; }

Note: both getData() and printData() should be conste. Further, printData()
in my eyes doesn't belong there at all, because it is easily achievable in
a more explicit and universal way with the free operator<< or with a
getData() call.

     int operator=(const Node& N) { return; }

Hmmm, interesting. Normally, operator= is supposed to assign something. Now
this one only returns the value of the right-hand side of the assignment.
What would be normal is this:

  Node& operator=(Node const& rhs)
    // note: not assigning 'next'!
    data =;
    return *this;

class List
     Node N;
     Node* top;
     int num_;

Your list contains a Node, a pointer to a Node and a signed number. If it's
a dynamic container, what is the single 'N' for?

     List(int num): num_(num) //create list
         top = new Node[num];
     ~List() //destroy list
         delete[] top;
     Node& operator[](int i) {return top[i]; }

Okay, one thing I can say now: you are never using Node::next, so you are
not actually coding a linked list here (as the name otherwise suggests) but
rather a dynamic array class. If you remove the 'next' pointer, all that
the Node class will contain is a single 'int', so in fact you could easily
replace the whole type with 'int', apart from a few function calls perhaps.

     void operator=(Node& N)
             //code to be placed here...

If you code this, it should assign to the list and not to a single object of
the list. That is what operator= in class Node would be for. However, what
is the meaning of assigning a 'Node' to a 'List'?

     void print()
        List L(num_);
        for(int i=0; i<num_; i++)
            cout << L[i];

 * This function should be const, see above explanations and also the FAQ.
 * Instead of printing the list this is invoked on, it creates a list with
the same number of arguments and prints each of its elements.
 * You could also overload operator<< for 'List'.


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