C++ :: Set Member To Same Value In All Instances Of Templated Structure

template <typename T> struct avl_tree {
T data;
int balance;
struct avl_tree <T> *Link[2];
static int (*comp)(T, T);
};

In main, I have a function like so:
int compare(int a, int b) {
return ( a - b );
}

Now how do I assign the function pointer in my avl_tree class to the compare function?

I did this:
int (avl_tree<int>::*comp)(int, int) = compare;

But I got the compiler error:
Tree_Test.cc: In function ‘int main()’:
Tree_Test.cc:27:42: error: cannot convert ‘int (*)(int, int)’ to
‘int (avl_tree<int>::*)(int, int)’ in initialization