[ns] How to get node's position in C++ codes?

Hi, all. I am trying to implement an algorithm in ns-2 which needs to get the node's position, say X and Y coordinate values, in C++ codes. Is there anybody can help. Any suggestion will be appreciated. ___ 好玩贺卡等你发，邮箱贺卡全新上线！

[ns] How to implement a mobility model?

Hello, all. I am trying to implement a new mobility model which I never touched before. Can anyone help me where the related codes reside? Any suggestion will be appreciated. Thanx in advaced. ___ 好玩贺卡等你发，邮箱贺卡全新上线！