So for example I defined p, remember back over here, as a Cartesian point, but I can actually ask for its polar form.

我可以要求返回它的极坐标形式，这里对我是可访问的，好，这很棒，请再记另外一个为什么。

麻省理工公开课 - 计算机科学及编程导论课程节选

That is to say, I'm going to go back to a node I've already visited.

也就是说我将要,返回我访问过的节点。

麻省理工公开课 - 计算机科学及编程导论课程节选