<p>I've been using Go for sometime now, and I just knew about this while reading <a href="http://www.gopl.io" rel="nofollow">The Go Programming Language</a> book.</p>
<pre><code>func main() {
s := []string{"one", "two", "three"}
for range s {
fmt.Println("hello")
}
}
</code></pre>
<p><a href="http://play.golang.org/p/yCe8U3AvPW" rel="nofollow">playground</a></p>
<p>to achieve the same behavior, I would've used the following and <code>gofmt</code> doesn't seem to care.</p>
<pre><code>func main() {
s := []string{"one", "two", "three"}
for _ = range s {
fmt.Println("hello")
}
}
</code></pre>
<p><a href="http://play.golang.org/p/jRL9KqenyS" rel="nofollow">playground</a></p>
<p>also I don't see this mentioned anywhere in the <a href="https://golang.org/doc/effective_go.html" rel="nofollow">Effective Go</a></p>
<hr/>**评论：**<br/><br/>SSoreil: <pre><p>This was an addition to the language in Go 1.4 or Go 1.5. Probably the reason why checkers do not yet pick it up.</p></pre>dominikh: <pre><p><a href="https://github.com/golang/lint/pull/196" rel="nofollow">https://github.com/golang/lint/pull/196</a></p></pre>Sphax: <pre><p>gofmt -s fixes the form with _</p></pre>superjew: <pre><p>Why would you want to range over something and not use it?</p></pre>KenjiTakahashi: <pre><p>Remember that for is the only loop and that you can range over different things (e.g. channels). For example, this will run some code every second to infinity:</p>
<pre><code>for range time.Tick(time.Second) {
doStuffEverySecond()
}
</code></pre></pre>randfur: <pre><p>Probably to build up another data structure with the same length.</p></pre>: <pre><p>[deleted]</p></pre>randfur: <pre><p>That's a syntax error.</p></pre>carrier_pigeon: <pre><p>s := []string{"one","two"}</p>
<p>i := len(s)</p>
<p>ss:=make([]string,i)</p></pre>weberc2: <pre><p>The time.Ticker uses a channel that yields a value once per period. Often you don't care about the value, but only want to block until the value is yielded.</p></pre>earthboundkid: <pre><p>It's usually only useful for channels where the channel value is only informative as a sync event.</p></pre>uzimonkey: <pre><p>I think it would be easier to just use a <a href="http://play.golang.org/p/XdxlSULPgb" rel="nofollow">more traditional for loop</a>. While it probably doesn't matter for such a small array, I'm not sure if the compiler would optimize away the actual array accesses and I'd rather not rely on a trick. It's also more clear, where I'd see the "for range s" and think "for range what? I'm iterating over something and not using it? Well, I suppose that'll just execute len(s) times then," but I know what the other for loop does immediately.</p></pre>LemurFromTheId: <pre><p>"Traditional" for loop is always prone to typos, and if you're not actually accessing the slice, you might not even get buffer overruns that would alert you to the problem - or worse: you might get them <em>elsewhere</em>. </p>
<p><strong>for range s { }</strong> is perfectly readable and obvious in intent to anyone who spends non-zero time working with Go: it executes <strong>{ }</strong> once for every element in <strong>s</strong>. It's also concise and it doesn't introduce unnecessary variables.</p></pre>dchapes: <pre><blockquote>
<p>would optimize away the actual array accesses</p>
</blockquote>
<p>There is no "array access" to "optimize away". For arrays <code>len(array)</code> is a compile time constant. For slices <code>len(slice)</code> is just a simple variable access, no computation required (unlike, for example, C's <code>strlen</code> or the length of a linked list). In either case if you have <code>for i := range foo</code> or <code>for range foo</code> (or even <code>for i, _ := range foo</code>) then elements of the array/slice are not accessed at all as part of the <code>for</code> statement.</p>
<p>The only case where those <code>for</code> loops wouldn't be simple counting loops is if <code>foo</code> was a string. <code>for i := range str</code> or <code>for range str</code> need to look through the bytes of the string looking for multibyte runes.</p></pre>
