c++ - Set member to same value in all instances of templated structure -

i have following struct:

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

what point comp function pointer valid function @ runtime, have instances of struct avl_tree<t> able access function.

int compare(int a, int b) {     return ( - b ); } 

is possible can like:

avl_tree<int> tree(new avl_tree<int>); tree = insert(tree, 9); std::cout << tree->comp(tree->data, 9) << '\n';//should print 0 

finally got answer this. solution:

in struct avl_tree:

typedef int (*compare)(t, t); static compare comp; 

above main:

template <typename t> int (*avl_tree<t>::comp)(t, t);//initialise pointer 

in main:

avl_tree<int>::comp = compare;//set static member function pointer function use 

in response previous question, here how can use it:

avl_tree<int> tree(new avl_tree<int>); tree = insert(tree, 9); std::cout << avl_tree<int>::comp(tree->data, 9) << '\n';//should print 0 

simple :d

declare comp static:

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

you can later assign particular template instance with:

avl_tree<int>::comp = int_compare; 

see this question , this outside site more information initialization of static members of template classes.