less
bool (*less)(struct rb_node *, const struct rb_node *))
if (less(node, parent))
bool (*less)(struct rb_node *, const struct rb_node *))
if (less(node, parent))
static void less(void);
{ '<', less },
int less;
less = heap->compare(elt, heap->array[idx]);
if (less)
int less;
less = 0;
less = -1;
less = 1;
if (less < 0)
else if (less > 0)