Well, this is one of the places where I want to come back to that highlighting of what do things do?
好,讲到这里我们得回去,看看高亮显示的关于程序,该怎么运行的注释吧?
So I wrote a little program called "chart" that, based on some data I happened to hardcode into the program, shows us their numbers for the past several years.
我写了一个叫做“图表“的小程序,基于我在程序中硬编码的一些数据,向我们显示在过去几年中我们课程的人数。
You notice what it did, it printed out that little, right up here I'd said enter a number and that's what it's printed out, so I can enter a number and it prints it out.
注意这个程序做了些什么,显示出了指定值,然后显示需要输入个数字,然后程序会显示这个数字,我输入一个数字然后程序显示了它。
And this picture kind of makes clear that we're headed for disaster.
这个程序稍微显示了,我们将走向灾难。
We're checking the end test and incrementing, actually I was going to, I commented that out for a reason you'll see in a second, but I, normally I would keep this on, which would let me, at each step, see what it's doing. If I ran this, it would print out each step. Which is helping me make sure that it's incrementing the right way.
对不对?进行终结测试然后递增,实际上我要,因为某些你们,马上要明白的原因我把这里注释了,但是我通常会一直这么做,这样能让我看到每一步都做了什么,如果我运行这个程序,它会在每一步都,进行显示,这能帮助我让我确信程序是,在以正确的方式递增。
And it still took it. And printed it up.
程序接受了输入,然后显示了这个字符串。
t prints out 0.
那么程序会怎么做呢?会显示答案为。
But that little short hand there is doing exactly the same thing. It is adding that value into some digits and putting it back or signing it back into some digits. And I'll walk through that loop and when I'm done I can print out the total thing does. And if I do that, I get out what I would expect.
加上得到的这个数的,但是这个缩写声明其实是进行了同样的操作,它把我们得到的这个数加到一个数上面去,然后用和对这个数进行了重新赋值,在循环中会去遍历字符串,当完成循环后,程序会显示数字的总和,如果我运行,这个程序的话,我会得到我期待的结果。
Remember last time, we wrote this simple piece of code to print out even or odd. If, you know, x, it was in fact, even or odd. So let me show you what a flow chart for that would look like, because I want to make a comparison point here.
记得上节课我们写过的,那个显示奇数还是偶数的程序么,如果,你知道,x,实际上是奇数还是偶数,那么让我来为大家画个这个程序的流程图吧,因为我这里想为大家做个比较。
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。
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