4 static void walk(const struct node *r, void (*action)(const void *, VISIT, int), int d)
11 action(r, preorder, d);
12 walk(r->a[0], action, d+1);
13 action(r, postorder, d);
14 walk(r->a[1], action, d+1);
15 action(r, endorder, d);
19 void twalk(const void *root, void (*action)(const void *, VISIT, int))
21 walk(root, action, 0);