blocks|key|1530030|text|我会把它的签名写成|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1530031|(runner+alen+blen+op)|offset|length|style|CODE|1530032|示例：|1530033|(runner+10+10+%2B)|1530034|entityMap^0|0|0|L|0|0|0|G|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@$D|P|E|Q|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|R|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|S|8|@$D|T|E|U|F|G]]|9|@]|A|$]]|$1|L|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|M|$]]

I would make its signature be something like

<code>(runner alen blen op)</code>

example:

<code>(runner 10 10 +)</code>

blocks|key|1530061|text|我不太确定我是不是在回答正确的问题。我在想，“如果我传递一个函数--一个符号而不是一个值--它如何使用符号所代表的值?这很接近吗？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1530062|(def+a+4)
(defn+my-inc+[x]+(%2B+(eval+x)+1))
user>+(my-inc+'a)
5|code-block|syntax|javascript|1530063|我相信还有一种比使用eval更优雅的方法。|1530064|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I'm not really sure i'm answering the correct question. I'm thinking "if i pass a function a symbol instead of a value how can it use the value that symbol represents? is that close?

<pre><code>(def a 4)
(defn my-inc [x] (+ (eval x) 1))
user&gt; (my-inc 'a)
5
</code></pre>

I'm sure there is a more elegant way than using eval.

blocks|key|1530095|text|函数参数总是在调用函数之前求值。如果要延迟计算或将某些计算或代码表示为对象，则有几个选项：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1530096|使用一个函数(见下面的代码)|ordered-list-item|1530097|使用宏并将一些代码拼接到宏生成的其他代码中。|1530098|将代码作为引号列表传递，并对其进行eval。|offset|length|style|CODE|1530099|使用函数是您想要做的99%25的时间。1%25的时间，你会想要宏。除非您在运行时生成代码或执行非常复杂的操作，否则永远不需要eval。|1530100|user>+(defn+runner+[f]
++++++++(doseq+[a+(range+3)
++++++++++++++++b+(range+3)]
++++++++++(println+a+b+(f+a+b))))
#'user/runner
user>+(runner+(fn+[x+y]+(%2B+x+y)))
0+0+0
0+1+1
0+2+2
1+0+1
1+1+2
1+2+3
2+0+2
2+1+3
2+2+4|code-block|syntax|javascript|1530101|这也可以写成(runner+#(%2B+%251+%252)，甚至可以简单地写成(runner+%2B)。|1530102|不需要将"a“和"b”作为参数传递到函数中。doseq和for介绍了它们自己的本地、词汇范围内的事物名称。他们没有理由使用a和b；任何名称都可以。fn的情况也是一样。我在这里使用x和y，因为这并不重要。|1530103|我也可以在a和b中使用fn，但它们将是与doseq看到的不同的a和b。如果这没有意义的话，你可能想读一读作用域。|1530104|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Scope_%2528programming%2529^0|0|0|0|H|4|0|1M|4|0|0|6|I|Y|A|0|5|1|9|1|M|5|S|3|1P|1|1R|1|21|2|2H|1|2J|1|0|5|1|7|1|B|2|K|5|V|1|X|1|1G|3|0|0^^$0|@$1|2|3|4|5|6|7|17|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|18|8|@]|9|@]|A|$]]|$1|E|3|F|5|D|7|19|8|@]|9|@]|A|$]]|$1|G|3|H|5|D|7|1A|8|@$I|1B|J|1C|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|1D|8|@$I|1E|J|1F|K|L]]|9|@]|A|$]]|$1|O|3|P|5|Q|7|1G|8|@]|9|@]|A|$R|S]]|$1|T|3|U|5|6|7|1H|8|@$I|1I|J|1J|K|L]|$I|1K|J|1L|K|L]]|9|@]|A|$]]|$1|V|3|W|5|6|7|1M|8|@$I|1N|J|1O|K|L]|$I|1P|J|1Q|K|L]|$I|1R|J|1S|K|L]|$I|1T|J|1U|K|L]|$I|1V|J|1W|K|L]|$I|1X|J|1Y|K|L]|$I|1Z|J|20|K|L]|$I|21|J|22|K|L]|$I|23|J|24|K|L]]|9|@]|A|$]]|$1|X|3|Y|5|6|7|25|8|@$I|26|J|27|K|L]|$I|28|J|29|K|L]|$I|2A|J|2B|K|L]|$I|2C|J|2D|K|L]|$I|2E|J|2F|K|L]|$I|2G|J|2H|K|L]]|9|@$I|2I|J|2J|1|2K]]|A|$]]|$1|Z|3|-4|5|6|7|2L|8|@]|9|@]|A|$]]]|10|$11|$5|12|13|14|A|$15|16]]]]

Function arguments are always evaluated before the function is called. If you want to defer evaluation or represent some computation or code as an object, you have a few options: 

<ol>
<li>Use a function (see my code below)</li>
<li>Use a macro and splice some code into some other code that the macro generates</li>
<li>Pass code as a quoted list, and <code>eval</code> it.</li>
</ol>

Using a function is what you want to do 99% of the time. 1% of the time, you'll want macros. You should never need <code>eval</code> unless you're generating code at runtime or doing very screwy things.

<pre><code>user&gt; (defn runner [f]
 (doseq [a (range 3)
 b (range 3)]
 (println a b (f a b))))
#'user/runner
user&gt; (runner (fn [x y] (+ x y)))
0 0 0
0 1 1
0 2 2
1 0 1
1 1 2
1 2 3
2 0 2
2 1 3
2 2 4
</code></pre>

This could also be written as <code>(runner #(+ %1 %2)</code> or even simply <code>(runner +)</code>.

There is no need to pass "<code>a</code>" and "<code>b</code>" into the function as arguments. <code>doseq</code> and <code>for</code> introduce their own local, lexically scoped names for things. There's no reason they should use <code>a</code> and <code>b</code>; any name will do. It's the same for <code>fn</code>. I used <code>x</code> and <code>y</code> here because it doesn't matter. 

I could've used <code>a</code> and <code>b</code> in the <code>fn</code> body as well, but they would have been a different <code>a</code> and <code>b</code> than the ones the <code>doseq</code> sees. You may want to read up on <a href="http://en.wikipedia.org/wiki/Scope_%28programming%29" rel="nofollow noreferrer">scope</a> if this doesn't make sense.

I want to be able to do the following pseudocode:

<ol>
<li>Pass in symbol a.</li>
<li>Pass in symbol b.</li>
<li>Pass in an expression using a and b</li>
<li>As I change the value of a and b, print the output of c at each moment.</li>
</ol>

Ideally, I would like the signature to look like:

<pre><code>(runner a b (+ a b))
</code></pre>

but I'm not sure that I'm approaching this correctly... I've tried changing the function to

<pre><code>(runner 'a 'b (+ 'a 'b))
</code></pre>

and this more complicated example:

<pre><code>(runner 'a 'b (+ (* 'a 'b) 'a))
</code></pre>

but this does a + on 'a and 'b before stepping into runner.

Here's my first stab at some clojure:

<pre><code>(defn runner [a b c] (
 (for [i (range 10)
 j (range 10)] (println i j (c i j))
</code></pre>

What concept of clojure am I missing?

How do I pass variables as variable names to a function?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我希望能够执行以下伪码：传递符号a。传入符号b。使用a和b传入表达式当我改变a和b的值时，每次打印c的输出。理想情况下，我希望签名看起来像：(runner a b (+ a b))但我不确定我是否正确地对待这件事..。我试过将函数更改为(runner 'a 'b (+ 'a 'b))这个更复杂的例子是：(runner ...

问如何将变量作为变量名传递给函数？
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问如何将变量作为变量名传递给函数？EN