blocks|key|357230|text|我猜你指的是a=b之类的东西？C:+d，其中b是条件，c是b为true时的值，d是b为false时的值。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|357231|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I assume you mean stuff like a = b ? c : d, where b is the condition, c is the value when b is true, and d is the value when b is false.

blocks|key|357241|text|在c%2B%2B中，没有实际的if部分。它被称为三元运算符。它的用法如下：？：；对于上面的示例，它将如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|357242|C+=+A+>+B+?+A+:+B;|code-block|syntax|javascript|357243|维基百科上的这篇文章也讨论了它：http://en.wikipedia.org/wiki/Ternary_operation|offset|length|357244|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Ternary_operation^0|0|0|G|1A|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

In c++ there's no actual if part of this. It's called the ternary operator. It's used like this: &lt;boolean statement&gt; ? &lt;result if true&gt; : &lt;result if false&gt;; For your example above it would look like this:

<pre><code>C = A &gt; B ? A : B;
</code></pre>

This article on wikipedia also discusses it:
<a href="http://en.wikipedia.org/wiki/Ternary_operation" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Ternary_operation</a>

blocks|key|3350014|text|它是这样工作的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3350015|expression+?+trueValue+:+falseValue|code-block|syntax|javascript|3350016|这基本上意味着如果expression的计算结果为真，将返回或执行trueValue，否则将返回或计算falseValue。|offset|length|style|CODE|3350017|请记住，只有在表达式为true或false时，才会分别计算和执行trueValue和falseValue。这种行为称为短路。|3350018|entityMap^0|0|0|9|A|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

It works like this:

<pre><code>expression ? trueValue : falseValue
</code></pre>

Which basically means that if <code>expression</code> evaluates to true, trueValue will be returned or executed, and falseValue will be returned or evaluated if not.

Remember that trueValue and falseValue will only be evaluated and executed if the expression is true or false, respectively. This behavior is called short circuiting.

blocks|key|352148|text|它是这样工作的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|352149|(condition)+?+true-clause+:+false-clause|code-block|syntax|javascript|352150|它最常用于赋值操作，尽管它也有其他用途。三元运算符?是一种缩短if-else子句的方法，在其他语言中也称为立即if语句(例如，VB中的IIf(condition,true-clause,false-clause))。|offset|length|style|CODE|352151|例如：|352152|bool+Three+=+SOME_VALUE;
int+x+=+Three+?+3+:+0;|352153|等同于|352154|bool+Three+=+SOME_VALUE;
int+x;
if+(Three)
++++x+=+3;
else
++++x+=+0;|352155|entityMap^0|0|0|P|1|1V|13|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@$I|Z|J|10|K|L]|$I|11|J|12|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|13|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|14|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|15|8|@]|9|@]|A|$]]|$1|S|3|T|5|D|7|16|8|@]|9|@]|A|$E|F]]|$1|U|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|V|$]]

It works like this:

<pre><code>(condition) ? true-clause : false-clause
</code></pre>

It's most commonly used in assignment operations, although it has other uses as well. The ternary operator <code>?</code> is a way of shortening an if-else clause, and is also called an immediate-if statement in other languages (<code>IIf(condition,true-clause,false-clause)</code> in VB, for example).

For example:

<pre><code>bool Three = SOME_VALUE;
int x = Three ? 3 : 0;
</code></pre>

is the same as

<pre><code>bool Three = SOME_VALUE;
int x;
if (Three)
 x = 3;
else
 x = 0;
</code></pre>

blocks|key|354642|text|我要说的是？是一条捷径。然而，一些“核心”程序员倾向于把它写得很长，这样在未来的情况下，人们就可以很容易地阅读和修改代码。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|354643|例如，如果您编写|354644|int+a+=+b<c+?+b+:+c;|code-block|syntax|javascript|354645|有些人声称这样写更清楚：|354646|if(b<c)
+a+=+b;
else
+a+=+c;|354647|因为在未来的情况下，人们可能会感染上它。当然，一个简单的b|354648|354649|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|T|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|U|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|V|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|W|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|X|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|Q|$]]

I would say the ? is a short-cut. However, some "hard-core" programmers tend to say write it out the long way so in future cases, people can easily read and modify code.

For example, if you write

<pre><code>int a = b&lt;c ? b : c;
</code></pre>

Some people claim that it's clearer to write:

<pre><code>if(b&lt;c)
 a = b;
else
 a = c;
</code></pre>

Because in future cases, people can catch it. Of course, a simple b&lt;c ? b:c is easy to catch, but sometimes complex operations are put in and it can be hard to spot.

blocks|key|3350113|text|似乎没有人提到条件运算符表达式的结果在C%2B%2B中可以是L值(但在C中不是)。下面的代码可以在C%2B%2B中编译并正常运行：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3350114|++++int+a,+b;
++++bool+cond;
++++a=1;+b=2;+cond=true;
++++(cond?+a+:+b)+=+3;
++++cout+<<+a+<<+","+<<+b+<<+endl;|code-block|syntax|javascript|3350115|上面的程序打印3，2|3350116|然而，如果a和b属于不同的类型，它将无法工作。以下代码给出了一个编译器错误：|3350117|++++int+a;
++++double+b;
++++bool+cond;
++++a=1;+b=2;+cond=true;
++++(cond?+a+:+b)+=+3;
++++cout+<<+a+<<+","+<<+b+<<+endl;|3350118|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

No one seems to mention that a result of conditional operator expression can be an L-value in C++ (But not in C). The following code compiles in C++ and runs well:

<pre><code> int a, b;
 bool cond;
 a=1; b=2; cond=true;
 (cond? a : b) = 3;
 cout &lt;&lt; a &lt;&lt; "," &lt;&lt; b &lt;&lt; endl;
</code></pre>

The above program prints 3, 2

Yet if a and b are of different types, it won't work. The following code gives a compiler error:

<pre><code> int a;
 double b;
 bool cond;
 a=1; b=2; cond=true;
 (cond? a : b) = 3;
 cout &lt;&lt; a &lt;&lt; "," &lt;&lt; b &lt;&lt; endl;
</code></pre>

blocks|key|354683|text|它很简单，它的基本语法是:表达式1?表达式2:表达式3；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|354684|如果表达式1为真，则表达式2将为真，否则表达式3将为真。|354685|示例：|354686|354687|+hey=24>2?24:34;|blockquote|offset|length|style|CODE|354688|354689|354690|在这里，条件是真的，24的值将被赋值给它。如果为false，则将为其分配34|354691|entityMap^0|0|0|0|0|1|F|0|0|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|U|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|V|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|W|8|@]|9|@]|A|$]]|$1|G|3|H|5|I|7|X|8|@$J|Y|K|Z|L|M]]|9|@]|A|$]]|$1|N|3|-4|5|6|7|10|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|11|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|12|8|@]|9|@]|A|$]]|$1|R|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|S|$]]

IT IS QUITE SIMPLE 
IT'S BASIC SYNTAX IS:
expression1?expression2:expression3;

If expression 1 is hold true then expression 2 will hold otherwise expression 3 will hold.

example:

<blockquote>
 <code>hey=24&gt;2?24:34;</code>
</blockquote>

here as condition is true value of 24 will be assigned to it.
if it was false then 34 will be assigned to it

blocks|key|3350216|text|简单地说，你可以将|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3350217|+写成|blockquote|offset|length|style|BOLD|3350218|3350219|3350220|C=(A>B)?A:B；|3350221|3350222|+这与：相同|3350223|3350224|3350225|if(A>B)

+C=A;

else

+C=B;|code-block|syntax|javascript|3350226|entityMap^0|0|1|2|0|0|0|0|0|1|3|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@$E|10|F|11|G|H]]|9|@]|A|$]]|$1|I|3|-4|5|6|7|12|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|13|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|15|8|@]|9|@]|A|$]]|$1|N|3|O|5|D|7|16|8|@$E|17|F|18|G|H]]|9|@]|A|$]]|$1|P|3|-4|5|6|7|19|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]|$1|R|3|S|5|T|7|1B|8|@]|9|@]|A|$U|V]]|$1|W|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]]|X|$]]

<blockquote>
 simply you can write this as
</blockquote>

C=(A>B)?A:B;

<blockquote>
 THIS IS SAME AS:
</blockquote>

<pre><code>if(A&gt;B)

 C=A;

else

 C=B;
</code></pre>

blocks|key|357402|text|这被称为“三元运算符”，?和:是编写if-else语句的另一种方式。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|357403|看看这个Codepen中的"Example+#1“，并取消注释它……你会注意到它做了什么。|357404|现在注释"Example+#1"，取消注释"Example+#2"，看看会发生什么。代码做的是完全相同的事情...但这一次只有5行代码。请注意，出现在?符号之前的内容是if+(条件)，而:之后出现的内容是要执行的内容。|357405|但是，如果你有一个需要"else-+if“(有2个以上可能的结果)的条件，就像Codepen的"Example+#3”中的那个(增加了用户写出特定错误答案的可能性)怎么办？那么三元运算符可能就没有那么有用了，但是您肯定可以用三元运算符连接多个条件，就像这个ES6+fizzbuzz示例一样。|357406|entityMap|0|LINK|mutability|MUTABLE|url|https://codepen.io/alfredrafael/pen/wvGLBLE?editors=0010|1|https://www.vincecampanale.com/blog/2016/12/16/fizzbuz-es6/^0|C|1|E|1|0|4|7|0|0|23|1|2C|2|2L|1|0|3O|8|1|0^^$0|@$1|2|3|4|5|6|7|V|8|@$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|10|8|@]|D|@$9|11|A|12|1|13]]|E|$]]|$1|H|3|I|5|6|7|14|8|@$9|15|A|16|B|C]|$9|17|A|18|B|C]|$9|19|A|1A|B|C]]|D|@]|E|$]]|$1|J|3|K|5|6|7|1B|8|@]|D|@$9|1C|A|1D|1|1E]]|E|$]]|$1|L|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|M|$N|$5|O|P|Q|E|$R|S]]|T|$5|O|P|Q|E|$R|U]]]]

This is called a &quot;Ternary operator&quot;, and the <code>?</code> and <code>:</code> are another way of writing an if-else statement.
Look at the &quot;Example #1&quot; in this <a href="https://codepen.io/alfredrafael/pen/wvGLBLE?editors=0010" rel="nofollow noreferrer">Codepen</a>, and un-comment it... you'll notice what it does.
Now comment &quot;Example #1&quot;, un-comment &quot;Example #2&quot;, and see what happens. The code does the exact same thing... but this time with only 5 lines of code. Notice how whatever appears before the <code>?</code> sign is the <code>if</code> (conditional), and whatever comes AFTER the <code>:</code> is the thing to be executed.
But what if you have a conditional that requires an &quot;else-if&quot; (with more than 2 possible outcomes) like the one in the Codepen's &quot;Example #3&quot; (which adds the possibility of the user writing a specific wrong answer)? Then the ternary operator might not be as useful, but you can certainly concatenate several conditions with the ternary operator, like on this ES6 <a href="https://www.vincecampanale.com/blog/2016/12/16/fizzbuz-es6/" rel="nofollow noreferrer">fizzbuzz</a> example.

blocks|key|352646|text|这就是我们的条件，如果'A‘为真，那么它会打印'B’，如果'A‘为假，它就会打印'C’。，如果‘A’为真，那么它会打印‘B’，如果‘A’为假，它就会打印‘C’。，‘a’，‘->’，‘A’，‘B’，‘C’。换句话说，我们也可以说这是if+else条件的另一种方式。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|352647|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

like this is our condition -&gt; A?B:C
So according to the condition if 'A' is True then it prints 'B' or if 'A' is false it prints 'C'.
In other words we can also say that it is an alternative way of if else condition.

I've always wondered how to write the <code>"A ? B : C"</code> syntax in a C++ compatible language.

I think it works something like: (Pseudo code)

<pre><code>If A &gt; B
 C = A
Else
 C = B
</code></pre>

Will any veteran C++ programmer please help me out?

How do I use the conditional (ternary) operator?

编译器

我一直想知道如何用C++兼容的语言编写"A ? B : C"语法。我认为它的工作原理是这样的：(伪代码)If A > B   C = AElse   C = B有没有经验丰富的C++程序员能帮帮我？

问如何使用条件(三元)运算符？
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