blocks|key|197213|text|正如所指出的(希望并不令人惊讶)，使用if%2Belse确实是在Go中执行条件句的idiomatic+way。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|197214|但是，除了完整的var%2Bif%2Belse代码块之外，这种拼写也经常使用：|197215|index+:=+val
if+val+<=+0+{
++++index+=+-val
}|code-block|syntax|javascript|197216|如果你有一个足够重复的代码块，比如int+value+=+a+<=+b+?+a+:+b的等价物，你可以创建一个函数来保存它：|197217|func+min(a,+b+int)+int+{
++++if+a+<=+b+{
++++++++return+a
++++}
++++return+b
}

...

value+:=+min(a,+b)|197218|编译器将内联这些简单的函数，因此它更快、更清晰、更简短。|197219|entityMap|0|LINK|mutability|MUTABLE|url|http://golang.org/doc/faq#Does_Go_have_a_ternary_form^0|J|7|13|D|0|0|8|B|0|0|H|Q|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@$9|13|A|14|1|15]]|E|$]]|$1|F|3|G|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|19|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1A|8|@$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|O|3|P|5|J|7|1D|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|1E|8|@]|D|@]|E|$]]|$1|S|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]]]

As pointed out (and hopefully unsurprisingly), using <code>if+else</code> is indeed the <a href="http://golang.org/doc/faq#Does_Go_have_a_ternary_form">idiomatic way</a> to do conditionals in Go.

In addition to the full blown <code>var+if+else</code> block of code, though, this spelling is also used often:

<pre><code>index := val
if val &lt;= 0 {
 index = -val
}
</code></pre>

and if you have a block of code that is repetitive enough, such as the equivalent of <code>int value = a &lt;= b ? a : b</code>, you can create a function to hold it:

<pre><code>func min(a, b int) int {
 if a &lt;= b {
 return a
 }
 return b
}

...

value := min(a, b)
</code></pre>

The compiler will inline such simple functions, so it's fast, more clear, and shorter.

blocks|key|197277|text|不带括号的map三元很容易阅读：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|197278|c+:=+map[bool]int{true:+1,+false:+0}+[5+>+4]|code-block|syntax|javascript|197279|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

The map ternary is easy to read without parentheses:

<pre><code>c := map[bool]int{true: 1, false: 0} [5 &gt; 4]
</code></pre>

blocks|key|197331|text|假设您有以下三元表达式(用C编写)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|197332|int+a+=+test+?+1+:+2;|code-block|syntax|javascript|197333|Go中惯用的方法是简单地使用if块：|offset|length|style|CODE|197334|var+a+int

if+test+{
++a+=+1
}+else+{
++a+=+2
}|197335|但是，这可能不符合您的要求。在我的例子中，我需要一个代码生成模板的内联表达式。|197336|我使用了一个立即求值的匿名函数：|197337|a+:=+func()+int+{+if+test+{+return+1+}+else+{+return+2+}+}()|197338|这可以确保两个分支都不会同时被评估。|197339|entityMap^0|0|0|E|2|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@$I|11|J|12|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|14|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|15|8|@]|9|@]|A|$]]|$1|S|3|T|5|D|7|16|8|@]|9|@]|A|$E|F]]|$1|U|3|V|5|6|7|17|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|X|$]]

Suppose you have the following ternary expression (in C):

<pre><code>int a = test ? 1 : 2;
</code></pre>

The idiomatic approach in Go would be to simply use an <code>if</code> block:

<pre><code>var a int

if test {
 a = 1
} else {
 a = 2
}
</code></pre>

However, that might not fit your requirements. In my case, I needed an inline expression for a code generation template. 

I used an immediately evaluated anonymous function:

<pre><code>a := func() int { if test { return 1 } else { return 2 } }()
</code></pre>

This ensures that both branches are not evaluated as well.

blocks|key|4703319|text|eold的回答很有趣，很有创意，甚至可能很聪明。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4703320|但是，建议改为执行以下操作：|4703321|var+index+int
if+val+>+0+{
++++index+=+printPositiveAndReturn(val)
}+else+{
++++index+=+slowlyReturn(-val)++//+or+slowlyNegate(val)
}|code-block|syntax|javascript|4703322|是的，它们都编译成本质上相同的程序集，但是这段代码比调用一个匿名函数返回一个原本可以写入变量的值更容易理解。|4703323|基本上，简单明了的代码比有创意的代码更好。|4703324|此外，任何使用map文字的代码都不是一个好主意，因为在Go中，map根本不是轻量级的。从Go+1.3开始，小地图的随机迭代顺序得到了保证，为了加强这一点，它在内存方面对小地图的效率要低得多。|4703325|因此，制作和删除大量的小地图既耗费空间又耗时。我有一段代码，它使用了一个很小的map+(可能是两个或三个键，但常见的用例只有一个条目)，但代码速度很慢。我们讨论的比使用双切片keyindex=>dataindex映射重写的相同代码至少慢3个数量级。而且可能更多。因为一些以前需要几分钟才能运行的操作开始在毫秒内完成。\|4703326|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

eold's answer is interesting and creative, perhaps even clever.

However, it would be recommended to instead do:

<pre><code>var index int
if val &gt; 0 {
 index = printPositiveAndReturn(val)
} else {
 index = slowlyReturn(-val) // or slowlyNegate(val)
}
</code></pre>

Yes, they both compile down to essentially the same assembly, however this code is much more legible than calling an anonymous function just to return a value that could have been written to the variable in the first place.

Basically, simple and clear code is better than creative code.

Additionally, any code using a map literal is not a good idea, because maps are not lightweight at all in Go. Since Go 1.3, random iteration order for small maps is guaranteed, and to enforce this, it's gotten quite a bit less efficient memory-wise for small maps.

As a result, making and removing numerous small maps is both space-consuming and time-consuming. I had a piece of code that used a small map (two or three keys, are likely, but common use case was only one entry) But the code was dog slow. We're talking at least 3 orders of magnitude slower than the same code rewritten to use a dual slice key[index]=>data[index] map. And likely was more. As some operations that were previously taking a couple of minutes to run, started completing in milliseconds.\

blocks|key|197427|text|func+Ternary(statement+bool,+a,+b+interface{})+interface{}+{
++++if+statement+{
++++++++return+a
++++}
++++return+b
}

func+Abs(n+int)+int+{
++++return+Ternary(n+>=+0,+n,+-n).(int)
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|197428|这将不会超过if/else，并且需要强制转换，但可以工作。仅供参考：|unstyled|197429|基准参考三进制-8+100000000+18.8+ns/op|197430|BenchmarkAbsIfElse-8+2000000000+0.27+ns/op|197431|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|N|8|@]|9|@]|A|$]]|$1|G|3|H|5|F|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|F|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|F|7|Q|8|@]|9|@]|A|$]]]|L|$]]

<pre><code>func Ternary(statement bool, a, b interface{}) interface{} {
 if statement {
 return a
 }
 return b
}

func Abs(n int) int {
 return Ternary(n &gt;= 0, n, -n).(int)
}
</code></pre>

This will not outperform if/else and requires cast but works. FYI:

BenchmarkAbsTernary-8 100000000 18.8 ns/op

BenchmarkAbsIfElse-8 2000000000 0.27 ns/op

blocks|key|4703386|text|Go+of+the中的惯用方法还有一个建议：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4703387|package+main

import+(
++++"fmt"
)

func+main()+{
++++val+:=+-5

++++index+:=+func+(test+bool,+n,+d+int)+int+{
++++++++if+test+{
++++++++++++return+n
++++++++}
++++++++return+d
++++}(val+>+0,+val,+-val)
++++
++++fmt.Println(index)
}|code-block|syntax|javascript|4703388|Go+Playground|offset|length|4703389|entityMap|0|LINK|mutability|MUTABLE|url|https://play.golang.org/p/Y_BCvG2EVoB^0|0|0|0|D|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]]]]

One more suggestion for the idiomatic approach in Go of ternary operator:
<pre class="lang-golang prettyprint-override"><code>package main

import (
 &quot;fmt&quot;
)

func main() {
 val := -5

 index := func (test bool, n, d int) int {
 if test {
 return n
 }
 return d
 }(val &gt; 0, val, -val)
 
 fmt.Println(index)
}
</code></pre>
<a href="https://play.golang.org/p/Y_BCvG2EVoB" rel="nofollow noreferrer">Go Playground</a>

In C/C++ (and many languages of that family), a common idiom to declare and initialize a variable depending on a condition uses the ternary conditional operator :

<pre><code>int index = val &gt; 0 ? val : -val
</code></pre>

Go doesn't have the conditional operator. What is the most idiomatic way to implement the same piece of code as above ? I came to the following solution, but it seems quite verbose

<pre><code>var index int

if val &gt; 0 {
 index = val
} else {
 index = -val
}
</code></pre>

Is there something better ?

What is the idiomatic Go equivalent of C's ternary operator?

编译器

在C/C++ (以及该系列中的许多语言)中，根据条件声明和初始化变量的常见习惯用法是使用三元条件运算符：int index = val > 0 ? val : -valGo没有条件运算符。实现上述相同代码的最常用的方式是什么？我得到了以下解决方案，但它似乎相当冗长var index intif val > 0 {   ...

问什么是相当于C的三元运算符的惯用Go？
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