184 lines
6.0 KiB
Plaintext
184 lines
6.0 KiB
Plaintext
<!DOCTYPE html>
|
|
<html>
|
|
<head>
|
|
<meta http-eqiv="content-type" content="text/html;charset=utf-8">
|
|
<title>Go by Example: Variables</title>
|
|
<link rel=stylesheet href="site.css">
|
|
</head>
|
|
<script type="text/javascript">
|
|
if (window.location.host == "gobyexample.com") {
|
|
var _gaq = _gaq || [];
|
|
_gaq.push(['_setAccount', 'UA-34996217-1']);
|
|
_gaq.push(['_trackPageview']);
|
|
(function() {
|
|
var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
|
|
ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
|
|
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
|
|
})();
|
|
}
|
|
</script>
|
|
<body>
|
|
<div class="example" id="variables">
|
|
<h2><a href="./">Go by Example</a>: Variables</h2>
|
|
|
|
<table>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>In Go, <em>variables</em> are explicitly declared and used by
|
|
the compiler to e.g. check type-correctness of function
|
|
calls.</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/Zv45CSMaiD"><img title="Run code" src="play.png" class="run" /></a>
|
|
<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre><span class="kn">import</span> <span class="s">"fmt"</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p><code>var</code> declares 1 or more variables.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre> <span class="kd">var</span> <span class="nx">a</span> <span class="kt">string</span> <span class="p">=</span> <span class="s">"initial"</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">a</span><span class="p">)</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>You can declare multiple variables at once.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre> <span class="kd">var</span> <span class="nx">b</span><span class="p">,</span> <span class="nx">c</span> <span class="kt">int</span> <span class="p">=</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">b</span><span class="p">,</span> <span class="nx">c</span><span class="p">)</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>Go will infer the type of initialized variables.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre> <span class="kd">var</span> <span class="nx">d</span> <span class="p">=</span> <span class="kc">true</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">d</span><span class="p">)</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>Variables declared without a corresponding
|
|
initialization are <em>zero-valued</em>. For example, the
|
|
zero value for an <code>int</code> is <code>0</code>.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre> <span class="kd">var</span> <span class="nx">e</span> <span class="kt">int</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">e</span><span class="p">)</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>The <code>:=</code> syntax is shorthand for declaring and
|
|
initializing a variable, e.g. for
|
|
<code>var f string = "short"</code> in this case.</p>
|
|
|
|
</td>
|
|
<td class="code">
|
|
|
|
<div class="highlight"><pre> <span class="nx">f</span> <span class="o">:=</span> <span class="s">"short"</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">f</span><span class="p">)</span>
|
|
<span class="p">}</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code">
|
|
|
|
<div class="highlight"><pre><span class="gp">$</span> go run variables.go
|
|
<span class="go">initial</span>
|
|
<span class="go">1 2</span>
|
|
<span class="go">true</span>
|
|
<span class="go">0</span>
|
|
<span class="go">short</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
|
|
<p class="next">
|
|
Next example: <a href="constants">Constants</a>.
|
|
</p>
|
|
|
|
<p class="footer">
|
|
by <a href="https://twitter.com/mmcgrana">@mmcgrana</a> | <a href="mailto:mmcgrana@gmail.com">feedback</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/variables">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
|
|
</p>
|
|
</div>
|
|
</body>
|
|
</html>
|