C++ Recursive Traversals with Function Pointers

Question

template <class T>
void BT<T>::inOrder(void (*inOrderPtr)(T&))
 {
     inOrderPtr(inOrder(this->root));
 }
template <class T>
void BT<T>::inOrder(Node<T>* root) const
 {
    if (root->left != NULL)
       inOrder(root->left);
       //something here
    if (root->right != NULL)
       inOrder(root->right);
 }

Ok I am trying to create this Traversal via recursion. I actually posted this problem before but I was going about it wrong due to me having to use a function pointer. I don't understand what I'm suppose to do. I've got the public wrapper that calls on the private one... but the public one is the one with the function being passed in so what do I even do with it?? I feel retarded so even if someone were to give me a small hint I'm sure I'd get it. I just don't know where to go from here.

an example of a code that calls on it is this:

first.inOrder(print_val)

Jim Buck · Accepted Answer · 2008-10-16 05:00:52Z

4

This is how to do it properly, but Node::GetItem needs implementing in order for this to be 100% correct:

template <class T>
T& Node<T>::GetItem() const
 {
    // TODO - implement getting a T& from a Node<T>
    return m_item; // possible implementation depending on Node's definition
 }

template <class T>
void BT<T>::inOrder(void (*inOrderPtr)(T&))
 {
    inOrder(this->root, inOrderPtr);
 }

template <class T>
void BT<T>::inOrder(Node<T>* root, void (*inOrderPtr)(T&)) const
 {
    if (root->left != NULL)
       inOrder(root->left, inOrderPtr);

    inOrderPtr(root->GetItem());

    if (root->right != NULL)
       inOrder(root->right, inOrderPtr);
 }

edited Oct 16, 2008 at 5:00

answered Oct 16, 2008 at 3:17

Jim Buck

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4 Comments

Doug Over a year ago

Wait why do I need to get T&? I was told I would only need a Public Wrapper and a private recursive function for this. So I'm not exactly sure what the GetNodeType is suppose to do.

Doug Over a year ago

I think within the scope of the assignment that isn't needed. it actually "functions" now. I have to fix a few other things with other functions... but this actually worked out good. Thanks so much.

Adam Mitz Over a year ago

Let's say Node looks like template <class T> class Node { T item_; }; then GetNodeType's body would be "return node->item_;"

Jim Buck Over a year ago

@Doug - Yeah, Adam's right. Since you have a Node<T> pointer, but the passed-in function needs a T&, you need to supply the code that gets a T from a Node<T>. It is mostly likely as simple as Adam's code snippet.

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