176 lines
7.3 KiB
Plaintext
Generated
176 lines
7.3 KiB
Plaintext
Generated
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Go by Example: Variables</title>
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<link rel=stylesheet href="site.css">
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</head>
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<script>
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onkeydown = (e) => {
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if (e.key == "ArrowLeft") {
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window.location.href = 'values';
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window.location.href = 'constants';
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<body>
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<div class="example" id="variables">
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<h2><a href="./">Go by Example</a>: Variables</h2>
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<table>
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<tr>
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<td class="docs">
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<p>In Go, <em>variables</em> are explicitly declared and used by
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the compiler to e.g. check type-correctness of function
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calls.</p>
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</td>
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<td class="code empty leading">
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<a href="https://go.dev/play/p/N5rWndIliJW"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">package</span> <span class="nx">main</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">import</span> <span class="s">"fmt"</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p><code>var</code> declares 1 or more variables.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="kd">var</span> <span class="nx">a</span> <span class="p">=</span> <span class="s">"initial"</span>
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</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">a</span><span class="p">)</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>You can declare multiple variables at once.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <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>
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</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">b</span><span class="p">,</span> <span class="nx">c</span><span class="p">)</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Go will infer the type of initialized variables.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="kd">var</span> <span class="nx">d</span> <span class="p">=</span> <span class="kc">true</span>
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</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">d</span><span class="p">)</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Variables declared without a corresponding
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initialization are <em>zero-valued</em>. For example, the
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zero value for an <code>int</code> is <code>0</code>.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="kd">var</span> <span class="nx">e</span> <span class="kt">int</span>
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</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">e</span><span class="p">)</span></span></span></code></pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>The <code>:=</code> syntax is shorthand for declaring and
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initializing a variable, e.g. for
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<code>var f string = "apple"</code> in this case.
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This syntax is only available inside functions.</p>
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</td>
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<td class="code">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">f</span> <span class="o">:=</span> <span class="s">"apple"</span>
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</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">f</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"><span class="p">}</span></span></span></code></pre>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td class="docs">
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</td>
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<td class="code">
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<pre class="chroma"><code><span class="line"><span class="cl"><span class="gp">$</span> go run variables.go
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</span></span><span class="line"><span class="cl"><span class="go">initial
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</span></span></span><span class="line"><span class="cl"><span class="go">1 2
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</span></span></span><span class="line"><span class="cl"><span class="go">true
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</span></span></span><span class="line"><span class="cl"><span class="go">0
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</span></span></span><span class="line"><span class="cl"><span class="go">apple</span></span></span></code></pre>
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</td>
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</tr>
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</table>
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<p class="next">
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Next example: <a href="constants">Constants</a>.
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</p>
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<p class="footer">
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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>
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</p>
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</div>
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<script>
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var codeLines = [];
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codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import \"fmt\"\u000A');codeLines.push('func main() {\u000A');codeLines.push(' var a \u003D \"initial\"\u000A fmt.Println(a)\u000A');codeLines.push(' var b, c int \u003D 1, 2\u000A fmt.Println(b, c)\u000A');codeLines.push(' var d \u003D true\u000A fmt.Println(d)\u000A');codeLines.push(' var e int\u000A fmt.Println(e)\u000A');codeLines.push(' f :\u003D \"apple\"\u000A fmt.Println(f)\u000A}\u000A');codeLines.push('');
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