preorder traversal using custom function

preorder.cpp

//
//  main.cpp
//  preorder
//
//  Created by Steve Myers on 11/20/14.

#include <iostream>
#include <array>

#include "binarySearchTree.h"

template<typename T>
class binaryTreeFuncTraverse : public bSearchTreeType<T>
{
    template<typename Func>
    void preorder(binaryTreeNode<T> *p, Func func) const
    {
        if (p != NULL)
        {
            func(p->info);
            preorder(p->llink, func);
            preorder(p->rlink, func);
        }
    }
    
public:
    template<typename Func>
    void preorderTraversal(Func func)
    {
        preorder(this->root, func);
    };
};

int main()
{
    const array<int, 8> testItems { 1, 10, 34, 56, 23, 11, 4, 15 };
    
    binaryTreeFuncTraverse<int> tree;
    for (const auto& item : testItems) tree.insert(item);
    
    int total = 0;
    
    tree.preorderTraversal( [&](const int& m) {
        total += m;
    });
    
    cout << "Total of all items in tree: " << total << endl;
    
    tree.preorderTraversal( [](int& m) {
        m = m * m;
    });
    
    cout << "Items in tree after squaring: " << endl;
    
    tree.preorderTraversal( [](const int& m) {
        cout << m << " ";
    });
    
//OUTPUTS:
    
//    Total of all items in tree: 154
//    Items in tree after squaring:
//    1 100 16 1156 529 121 225 3136
    
    return 0;
}