#include<iostream>
template <typename T> struct avl_tree {
T data;
int balance;
struct avl_tree <T> *Link[2];
int (*comp)(T, T);
};
int compare(int a, int b) {
return ( a - b );
}
int main()
{
avl_tree<int> *tree =new avl_tree<int>;
tree->data=9;
tree->comp =compare;
std::cout << tree->comp(tree->data, 9) << '\n';
}
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