<p><a href="https://play.golang.org/p/ceQ9w5GjUQ">https://play.golang.org/p/ceQ9w5GjUQ</a></p>
<p>Here the function "fun" takes in "boom" variable of type string, but makes no use of it in the function body. Still the code compiles and run's fine. Why is that so taking into account Go's strict rules about unused variables. Though it looks totally harmless, could it have any side effects ?</p>
<hr/>**评论：**<br/><br/>james-h: <pre><p>If you want to create an interface, then you probably don't know exactly how each concrete implementation of that interface will behave, and so it would be unreasonable to require all implementations to make use of all variables. Since methods are functions, the same rule applies to all functions, even those that aren't methods.</p>
<p>That being said, I think it would have made sense to force the following:</p>
<pre><code>func boom(_ string) {
fmt.Println("Having funnnnn")
}
</code></pre>
<p>I think you're right that it's sort of inconsistent of Go to allow unused parameters.</p></pre>gkx: <pre><p>I think it's definitely a good point to force the underscore. I wonder if that's a change that would be reasonable or if it would break too much code.</p></pre>james-h: <pre><p>It certainly would, so don't hold your breath. This feature won't make its way into Go 1.x.</p></pre>eatingthenight2: <pre><p>I was amazed the first time I used _ as a parameter and go let me after yelling at me for just about everything else when I was learning it.</p></pre>natefinch: <pre><p>Yep, I agree.</p></pre>klaaax: <pre><p>well, no Go works the same way for variables and functions</p>
<p>AFAIK you cannot declare local functions if they are not closures ,but you can declare closures on the local scope.</p>
<p>AND</p>
<p>if you declare a variable on the global scope, even a private one, you don't have to use it.</p>
<pre><code> package main
var x = 2
func main(){}
</code></pre>
<p>will compile without errors.</p></pre>skelterjohn: <pre><p>Two things come into play, here.</p>
<p>First, for a method (which is basically the same thing as a function) to help a type satisfy an interface, it has to have all the parameters whether it uses them or not.</p>
<p>Second, given that we must have all parameters, we can't have <em>some</em> of them named and <em>some</em> of them unnamed. It would be grammatically ambiguous since we can have "func foo(x, y string)". Is x a type or is it a string? The grammar says it's a string.</p></pre>natefinch: <pre><p>Well, you can do func (foo) Bar(_, y string) to satisfy an interface but show that you're not using x.</p></pre>skelterjohn: <pre><p>Oh my, I didn't realize that was possible. I figured it would be a compile error :)</p></pre>pierrrre: <pre><p>interface</p></pre>
