<p>So I want to refresh my knowledge of Go (I haven't programmed in it in a while), and I'm taking the tour of Go, and I came across this example
<a href="https://tour.golang.org/moretypes/25">https://tour.golang.org/moretypes/25</a></p>
<pre><code>package main
import "fmt"
func adder() func(int) int {
sum := 5
return func(x int) int {
sum += x
return sum
}
}
func main() {
pos, neg := adder(), adder()
for i := 0; i < 10; i++ {
fmt.Println(
pos(i),
neg(-2*i),
)
}
fmt.Println(pos(10))
}
</code></pre>
<p>I don't understand why the <code>sum</code> variable in <code>adder()</code> behaves like a static one. Sorry if this is the wrong place to ask such questions</p>
<hr/>**评论：**<br/><br/>HereComesDrTran: <pre><p>The example talks about "function closures" which is what is causing what you're seeing. Here's some extra reading on it: <a href="http://keshavabharadwaj.com/2016/03/31/closure_golang/" rel="nofollow">http://keshavabharadwaj.com/2016/03/31/closure_golang/</a></p></pre>Maplicant: <pre><p>Off-topic, but this is the ideal website to me. Clean, pretty, no ads and not bloated with JavaScript widgets.</p></pre>HereComesDrTran: <pre><p>Agreed, props to the author for that for sure</p></pre>budkin: <pre><blockquote>
<p>In other words, the function defined in the closure ‘remembers’ the environment in which it was created</p>
</blockquote>
<p>ah, right! thanks! now it makes sense</p></pre>qwer7y: <pre><p>Ahhh. Yes. Thanks a bunch, stranger!</p></pre>9nut: <pre><p><a href="https://golang.org/ref/spec#Function_literals" rel="nofollow">https://golang.org/ref/spec#Function_literals</a></p></pre>ChurroLoco: <pre><p>The reading posting in the comments is good. To add onto those, think what is in the variables of 'pos' and 'neg' as data and logic together. Both the data and logic in those variables will stay around as long as the variables remain in scope. In this case the will remain until and end of the program since they are in main.</p></pre>
