finally got the idea of how to implement my own avl tree lib. it's different from Ben Pfaff's libavl, and mine will definitely be slower. i'm confident in that aspect. ;) me just got a different way to structure the function-calls' in my lib.
(why reinvent the wheel, and badly?) (i stared at my display for ten minutes trying to get a clever answer but failed. i humbly left this question to the reader.)