We talked about things you could do to try make sure that happens.

我们提到过过你们能做什么,并且确信那会发生。

麻省理工公开课 - 计算机科学及编程导论课程节选

I think the easiest way to look at what this does, is let's take a really simple example- I want to make sure I put the right things out- I've got a simple little list of values there.

到底做了什么，就是让它跑一个简单的例子，我想要确信我找到了正确的元素-,这里我用一个简单的小的列表-,如果我去代码里面看。

麻省理工公开课 - 计算机科学及编程导论课程节选

But notice what this does. The first thing it does is, it says, let's check and make sure x is greater than or equal to 0. If it isn't, notice what's going to happen. None of that block is going to get executed, and it's going to come down here and print out a useful piece of information, which says, hey, you gave me a negative number. I don't know how to do this.

做的是和以前一样的事情,但是注释它做了什么，第一件做的事情就是,程序说，要去检查并且确信x是大于等于0的，如果不是的话，请注意会发生什么,下面的代码都不会被执行,程序会到这里来然后显示一些有用的信息,信息会说，嘿，你给了我一个负数,我不知道该怎么弄这个了。

麻省理工公开课 - 计算机科学及编程导论课程节选