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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example: For</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'constants';
}
if (e.key == "ArrowRight") {
window.location.href = 'if-else';
}
}
</script>
<body>
<div class="example" id="for">
<h2><a href="./">Go by Example</a>: For</h2>
<table>
<tr>
<td class="docs">
<p><code>for</code> is Go’s only looping construct. Here are
some basic types of <code>for</code> loops.</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="http://play.golang.org/p/2-4H-ArwHHS"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kn">import</span> <span class="s">"fmt"</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>The most basic type, with a single condition.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">i</span> <span class="o">:=</span> <span class="mi">1</span>
<span class="k">for</span> <span class="nx">i</span> <span class="o"><=</span> <span class="mi">3</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">i</span><span class="p">)</span>
<span class="nx">i</span> <span class="p">=</span> <span class="nx">i</span> <span class="o">+</span> <span class="mi">1</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>A classic initial/condition/after <code>for</code> loop.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="k">for</span> <span class="nx">j</span> <span class="o">:=</span> <span class="mi">7</span><span class="p">;</span> <span class="nx">j</span> <span class="o"><=</span> <span class="mi">9</span><span class="p">;</span> <span class="nx">j</span><span class="o">++</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">j</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>for</code> without a condition will loop repeatedly
until you <code>break</code> out of the loop or <code>return</code> from
the enclosing function.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="k">for</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"loop"</span><span class="p">)</span>
<span class="k">break</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>You can also <code>continue</code> to the next iteration of
the loop.</p>
</td>
<td class="code">
<pre class="chroma">
<span class="k">for</span> <span class="nx">n</span> <span class="o">:=</span> <span class="mi">0</span><span class="p">;</span> <span class="nx">n</span> <span class="o"><=</span> <span class="mi">5</span><span class="p">;</span> <span class="nx">n</span><span class="o">++</span> <span class="p">{</span>
<span class="k">if</span> <span class="nx">n</span><span class="o">%</span><span class="mi">2</span> <span class="o">==</span> <span class="mi">0</span> <span class="p">{</span>
<span class="k">continue</span>
<span class="p">}</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">n</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="gp">$</span> go run for.go
<span class="go">1
</span><span class="go">2
</span><span class="go">3
</span><span class="go">7
</span><span class="go">8
</span><span class="go">9
</span><span class="go">loop
</span><span class="go">1
</span><span class="go">3
</span><span class="go">5</span></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>We’ll see some other <code>for</code> forms later when we look at
<code>range</code> statements, channels, and other data
structures.</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
Next example: <a href="if-else">If/Else</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> and <a href="https://eli.thegreenplace.net">Eli Bendersky</a> | <a href="https://github.com/mmcgrana/gobyexample">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
</p>
</div>
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