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And then I say, oh you know I've used lists all over this program. I'll bet this isn't the only place where I've made this mistake.
变化引起的边缘效应，然后我的意思是,你知道的我在这个程序中一直都在用数组,我敢打赌我犯了这种错不止一次。
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So an adversary who's actually trying to break your programs 'cause frankly too much software these days is not written with a paranoia in mind.
或者说是你的敌人,而且千方百计地要破坏你的程序,唉，这种漏洞百出的软件我见过的是在太多了。
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What I don't want your program to do is crash when that happens. Or run forever.
当这种问题出现时程序崩溃,或者一直运行下去。
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So I propose this algorithm, this program, this process for counting people in this room.
因此我提出了这种算法，这种程序和处理方法,来计算教室里的人数。
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To do that, we need to describe: not only, what are the primitives, but how do we capture things legally in that language, and interact with the computer?
为了达到这个目的，我们需要描述：,包括程序基本的东西，以及怎么在这种语言中，做我们想做的事情并和计算机交互？
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Whenever I think about how to build an interesting program, and I hope whenever you think about it, the first thing I think about is, what are the classes I might want to have, what are the types?
无论我何时,去想怎样建立一个有趣的程序，你们每次做这种思考的时候，你们想得第一件事，就是我应该要有什么类呢，它们是什么类型的呢？
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So writing a program at least in this language is a two-step process.
用这种语言写一个至少需要,两步完成的小程序。
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And it's called Silly because it's really a rather ugly program. It's certainly not the right way to write a program to do this.
它之所以被称为Silly因为,它实在是一个相当丑的程序,当然以这种方式去写一个程序是不对的。
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- Now that's a slight lie-- or actually in these days of political debates, a slight misspeaking, a wonderful word-- -- it is technically correct. It is enough to allow us to write any program, but it's not enough to allow us to easily write any program.
现在还有点说谎的感觉,或者在这些强调政治辩论的日子中，可以说成是有些词不达意-,这是一个绝妙的形容词,在语义上是完全正确的，用这种语言我们可以编写任何程序,但是不能轻松地编写程序。
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Remember last time, I said that there's different kinds of complexity in our code, and I suggested for simple branching programs, the amount of time it takes to run that program is, in essence, bounded by the number of instructions, because you only execute each instruction at most once.
但是这里有个很重要的点,记得上节课，我提过在我们的代码中，有不同种类的复杂度，而且我还说了对于简单的分支程序,运行这种程序需要的总体时间,大体上，是和指令的数目相关的,因为每个指令只会被执行最多一次。
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I've certainly written code that has this problem, I've tried to use my own code that has this problem, and good to us, right, good hygiene, I'm going to use that word again here, of getting into the habit of writing defensive code up front, it's part of that collection of things that you ought to do is a great thing to do.
我举手了吧？,我当然写过犯这种错误的程序了,我也尝试过应用含有这种错误的代码，不错，好的卫生，我还是要用这个词,对我们有帮助，养成写防卫性,代码的好习惯，是你应该做的,一系列事情之一,也是我们日后要做的主要的事情。
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So just in case I happen to use the CS50 library, we've configured the cloud in such a way that make just always provides you with access to it.
所以万一我碰巧使用了CS50程序库，我们用这种方法配置了联网,那样我们就有使用它的权利了。
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And you might have started doing these kinds of things in Scratch as your programs got more sophisticated.
并且你可能已经开始在Scratch中开始做这种事情了,随着你们的程序变得越复杂。
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Scratch The syntax actually looks reminiscent to Scratch, where you have a puzzle piece reminiscent of this shape, but you have to say "if" followed by a space, followed by in parenthesis, the Boolean expression that you want to check -- more on those in a moment.
这个语法看起来使人想起，那里有一个这种形状的程序块，但是你必须说明“if“后面跟着一个空格，跟着一个括号，一个你需要核对的布尔表达式,-还有更多的。
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