<pre><code>package main
import "fmt"
func main() {
var a [4]int
a[0] = 1
a[1] = 2
a[2] = 3
a[3] = 4
fmt.Println(a)
//Inplace swap - how come this works?
a[0], a[1] = a[1],a[0]
fmt.Println(a)
}
</code></pre>
<p><a href="https://play.golang.org/p/awDpqht3NX">https://play.golang.org/p/awDpqht3NX</a></p>
<p>Shouldn't a[0]=2 and a[1]=2 ?</p>
<hr/>**评论：**<br/><br/>hanmunjae: <pre><p>The RHS is evaluated before any assignments are done. <a href="https://golang.org/ref/spec#Assignments">https://golang.org/ref/spec#Assignments</a></p></pre>weberc2: <pre><p>By "evaluated", you mean something like a temp variable is created to store off the evaluation of the array indexing?</p></pre>hanmunjae: <pre><p>You can think of it like that, yes. Not just array indexing, but the value of every expression on the right hand side of the "=".</p></pre>weberc2: <pre><p>Yeah, thanks for confirming. I tried the following experiment to test if it was a facet of array indexing or any expression:</p>
<pre><code>a := 0
b := 1
a, b = b, a
</code></pre></pre>9nut: <pre><p>it's in the language spec:
<a href="https://www.google.com/?gws_rd=ssl#q=site:golang.org+%22The+assignment+proceeds+in+two+phases.%22">https://www.google.com/?gws_rd=ssl#q=site:golang.org+%22The+assignment+proceeds+in+two+phases.%22</a></p></pre>avsej: <pre><p>what if equals is a function? in this case it would be natural to put copies of the arguments to the stack and call the function</p>
<p><a href="https://play.golang.org/p/9eJJmvmot5" rel="nofollow">https://play.golang.org/p/9eJJmvmot5</a></p></pre>kpmy: <pre><p>Objects (one object, whatever) on the left and values of objects on the right. First you take (calculate) values, then do the assignment. </p></pre>
