So again, we should be able to check all of our formal charges and make sure they add up to 0, which they do, and that makes sense, because we have a neutral atom in terms of thionyl chloride.

因此同样地，我们可以检验一下,我们所有的形式电荷是否正确,确保它们加起来等于零，而它们确实是这样，这是合理的，因为亚硫酰氯是一个中性原子。

麻省理工公开课 - 化学原理课程节选

That is we'd like to be able to get pieces of them out. We'd like to be able add them together or concatenate them together.

我们也可以对字符串进行切片,实际上这些都可以,因此字符串也支持选择，切片。

麻省理工公开课 - 计算机科学及编程导论课程节选

I want to just use it, I shouldn't have to worry about what variables I use inside of it, I have shouldn't have to worry about where that is in the code, I should be able to just abstract it away. And that's what we want to add today, are those two things.

我只是想使用它,我不用考虑我在这段代码中,使用的是什么变量,我完全不用考虑代码的内容,只要抽象就好,我们今天想补充的内容就是这两点。

麻省理工公开课 - 计算机科学及编程导论课程节选