Question

This a const member function, which allow me to get the minimum node of the tree:

BinarySearthTree* BinarySearchTree::min() const                                        
{                                                                                      
    // Return the minimum node (left-most node) value of the tree                      
    BinarySearchTree * next = (BinarySearchTree *) this;                               

    for (next ; next != NULL; next = next->pLeft)                                      
        if (next->pLeft == NULL)                                                       
            return next;                                                               
}

I have to cast down the const-ness of ‘this’ pointer when assigning it to ‘next’, but this actually rises the potential that I may modify the value of what ‘this’ points to? Rather than always remind myself not to modify whatever ‘next’ points to, is there a way to prevent it happening by a better designing of the function?

Answer 1

Make next const:

const BinarySearthTree* BinarySearchTree::min() const                                        
{                                                                                      
    // Return the minimum node (left-most node) value of the tree                      
    const BinarySearchTree *next;                               

    for (next = this; next != NULL; next = next->pLeft)                                      
        if (next->pLeft == NULL)                                                       
            return next;
    return NULL;                                                               
}