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Right, having done that, we can certainly get to more complicated things, so for example, suppose I look at that expression.
好，说完了这一点，我们就可以讲些复杂些的话题了，例如，假设我看到了这个表达式。
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And here, too, it's just a little baby program in that I'm hardcoding the expression 17 divided by 13.
然后这里，这只是一个子程序,在那里面我硬编码了表达式“17除以13“
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Literally, return the control from this function, and take the value of the next expression, and return that as the value of the whole computation.
正如字面意义上说的，从这个函数返回，然后取得下一个表达式的值,并把这个值作为整个计算的结果返回。
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It's really amazing that what Newton did in the case of gravity was to find the expression for this.
这一点非常神奇,牛顿在引力方面的研究,只是为了找出这个的表达式
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So what we're going to do is set these two things equal to each other, put in stars here.
我们只需要令这两个表达式相等,在这里标注上*号
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It's a very important point, if you see the very simple math that I'm showing up here.
这一点要特别注意，看看这个简单的数学表达式。
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I can substitute dq from this expression in here.
代入这个表达式的这里。
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And now, if I'm touching mouse pointer, we saw that Boolean expression before, play sound meow, wait a couple of seconds, and then just keep checking.
现在，如果我们碰下鼠标指针，起初我们看到一个布尔表达式，播放猫叫的声音，等几秒钟，然后如刚才那样做检测。
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And this puzzle piece here colored in blue because it's a Boolean expression is just something that--whose answer is either a yes or no, 0 true or false, one or zero.
这个拼图染成蓝色,因为它是布尔表达式,它的结果只可能是肯定或否定，对或错，1或者。
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which I just did there, -mystring in fact, let me type it in-- mystring, with an equal sign, which is saying, assign or bind to that name the value of the following expression.
也就是这里我做的，实际上，让我输入，然后是个蹬好，意思就是说，把这个名字绑定到,后面表达式的值上去。
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That code says the following: the IF says, I've got an expression, I'm going to evaluate it.
代码的含义是这样的：,我有一个表达式，我会去对这个表达式求值。
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And so, in fact, if I wanted the other version of it, in fact, if I do this right, 23 it's going to give me 23 because it does the multiplication first, if I wanted the other version of it, Python I need to tell it that, by using, excuse me, parentheses.
因此，实际上，如果我想换种做法，实际上，如果我去执行这个表达式，返回值是3,因为乘法会被优先执行，如果我需要换种做法，我需要告诉，用括号来告诉它。
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So, Newton did not ever tell you what the expression for force is in a given context.
牛顿从来也没有告诉过你,在这种情况下力的表达式
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I want you not to memorize every formula the book gives you for this problem.
我希望你们不要机械性地记忆,书上所给的这个问题的表达式
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Now, you've already seen how entropy depends on temperature.
如何来求熵的表达式,现在你已经知道熵对温度的依赖关系。
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We can start having complex expressions, you can imagine we can have things are lots of parens, and all sorts of things in it. Yes, question.
我们可以开始写复杂点的表达式了，你可以想象,我们有一个很多括号的表达式，里面有各种各样的东西，什么问题。
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I know you'd like to give me other things, other expression, somebody give me a number.
表达式什么的，谁给我一个数字？,没有么？谢谢！很不错的数字。
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What I'm doing, by the way, here is I'm simply typing in expressions to that interpreter.
顺路说一下，我正在做的就是给计算器传入,一个表达式。
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What do you think should happen if I evaluate that expression?
你认为我对表达式求值的话,会发生什么？
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The answer was, find a mathematical expression depending on the number of inputs.
很不错，答案是，找到一个通过输入数字,计算出来的数字表达式。
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What I'm going to do here is I'm going to substitute in for prices.
接下来我要用表达式来替换价格
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If you have not seen the calculus that I'm about to use on the board, or more likely, if you've forgotten it since high school, don't panic.
如果你们没有见过我将要,在板书上写的表达式,或者说,高中毕业你们就忘了,没关系
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So, for example, there's an expression.
那么，例如，这里有个表达式。
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Well, there's a formula that's been used by bond traders for hundreds of years and it's a traditional expression, which goes from the discount rate to the price.
这里有个债券交易商,用了上百年的公式,这是个传统表达式,它能用折扣率算得价格
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And I'm going to rewrite it now with that P expanded out.
我把它代入到这个表达式然后展开
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What I have now is the following: I can write expressions, do combinations of things to get out values, I can store them away, I can print them up.
我已经讲过如下内容：,如何写表达式，如果把东西混合然后得到结果值，我可以将其保存，也可以将其显示。
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x It says, take the name x and create a binding for that name to the value of the sub-expression and in fact to do this, to stress a point, let's do that.
它的意思是，创建了一个名字,然后创建了对于这个名字,和子表达式的值的绑定,实际上这么做，我们是为了，要强调一个点，让我们来说说这个点。
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I just want to remind you, if I wanted to, for example, type in an expression like that, notice the syntactical form, it's an expression, a number, followed by an operand, followed by another expression.
我想要提醒下大家，如果你想要，例如，输入一个这样的表达式，注意语法形式，这是个表达式，一个数字，后面是一个运算对象，后面是另外一个表达式。
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In there, I want to make this distinction, this nuance: the evaluator is still going to be taking those expressions and using its rules to get a value, but it's not going to print them back out.
在这里，我想要做这么一个，细微差别：运算器依然会,对表达式,进行求值，但是不会,显示结果值。
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Scratch This Boolean expression allows you to say to scratch if you are touching the mouse pointer, the little arrow, do something. How do we do something?
布尔表达式允许你告诉,当你触碰到鼠标指针，也就是小箭头，程序就相应地做一些事情？
应用推荐