Because I could've built that in, it says if you change the value of this thing, by the way you need to change recompute those other values in order to make this hold up.

我想要大家通过定义好的方法，来改变实例的值了,因为我可以把这个功能，内置到方法里面去,它的意思就是如果,你改变一个值。

麻省理工公开课 - 计算机科学及编程导论课程节选

And if you're going from Boston to someplace else where New York just happens to be on the way, it doesn't have to recompute that part of it.

如果你是从波士顿到其他地方,而碰巧路过纽约你就不需要，重新计算从波士顿到纽约这段路了。

麻省理工公开课 - 计算机科学及编程导论课程节选