Set default parameter to nullptr and non-static class fields in C++

Question

I am building a binary search tree and the following is the add function:

void BinaryTree::add(int value, Node*& node, Node*& parent) {
    if(!node) {
        node = new Node(value);
        node->parent = parent;
    }
    else if(node->key < value)
        this->add(value, node->rightNode, node);
    else if(node->key > value)
        this->add(value, node->leftNode, node);
}

I want to set default parameters for the last two (node, parent) parameters:

void add(int value, Node*& node = root , Node*& parent = nullptr);

where root is a field of the class.

This does not seem to work for either case. How shall I implement it and what is wrong here? Thanks!

`void add(int value, Node* node = root , Node* parent = nullptr)` — anthonyvd, Jul 09 '13 at 19:45
@ShafikYaghmour You're right, although I have to admit that's probably not the best binary search tree design I've seen — anthonyvd, Jul 09 '13 at 19:46
References need to be initialized to a valid object, which means not a `nullptr`: http://stackoverflow.com/questions/4364536/c-null-reference — Shafik Yaghmour, Jul 09 '13 at 19:46
I think I have to pass the pointers by reference since I am assigning values to the pointers. — Ra1nWarden, Jul 09 '13 at 19:48

score 5 · Accepted Answer · answered Jul 09 '13 at 19:57

5

You can't initialize references to nullptr. They has to be valid objects. To make root defualt object you may add new function with same name

void BinaryTree::add(int value) {
    Node* emptyParent = nullptr;
    add(value, root, emptyParent); 
}

answered Jul 09 '13 at 19:57

RiaD

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Set default parameter to nullptr and non-static class fields in C++

1 Answers1