185 lines
6.7 KiB
Plaintext
185 lines
6.7 KiB
Plaintext
<!DOCTYPE html>
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<html>
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<head>
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<meta http-eqiv="content-type" content="text/html;charset=utf-8">
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<title>Go by Example: If/Else</title>
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<link rel=stylesheet href="site.css">
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<div class="example" id="if-else">
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<h2><a href="./">Go by Example</a>: If/Else</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Branching with <code>if</code> and <code>else</code> in Go is
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straight-forward.</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="http://play.golang.org/p/p_ykufAYRj"><img title="Run code" src="play.png" class="run" /></a>
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<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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</pre></div>
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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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<div class="highlight"><pre><span class="kn">import</span> <span class="s">"fmt"</span>
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</pre></div>
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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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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
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</pre></div>
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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>Here’s a basic example.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="k">if</span> <span class="mi">7</span><span class="o">%</span><span class="mi">2</span> <span class="o">==</span> <span class="mi">0</span> <span class="p">{</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"7 is even"</span><span class="p">)</span>
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<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"7 is odd"</span><span class="p">)</span>
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<span class="p">}</span>
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</pre></div>
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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 have an <code>if</code> statement without an else.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="k">if</span> <span class="mi">8</span><span class="o">%</span><span class="mi">4</span> <span class="o">==</span> <span class="mi">0</span> <span class="p">{</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"8 is divisible by 4"</span><span class="p">)</span>
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<span class="p">}</span>
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</pre></div>
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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>A statement can precede conditionals; any variables
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declared in this statement are available in all
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branches.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="k">if</span> <span class="nx">num</span> <span class="o">:=</span> <span class="mi">9</span><span class="p">;</span> <span class="nx">num</span> <span class="p"><</span> <span class="mi">0</span> <span class="p">{</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">num</span><span class="p">,</span> <span class="s">"is negative"</span><span class="p">)</span>
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<span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="nx">num</span> <span class="p"><</span> <span class="mi">10</span> <span class="p">{</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">num</span><span class="p">,</span> <span class="s">"has 1 digit"</span><span class="p">)</span>
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<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">num</span><span class="p">,</span> <span class="s">"has multiple digits"</span><span class="p">)</span>
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<span class="p">}</span>
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<span class="p">}</span>
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</pre></div>
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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>Note that you don’t need parentheses around conditions
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in Go, but that the brackets are required.</p>
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</td>
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<td class="code empty">
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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 leading">
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<div class="highlight"><pre><span class="gp">$</span> go run <span class="k">if</span>-else.go
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<span class="go">7 is odd</span>
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<span class="go">8 is divisible by 4</span>
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<span class="go">9 has 1 digit</span>
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</pre></div>
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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>There is no <a href="http://en.wikipedia.org/wiki/%3F:">ternary if</a>
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in Go, so you’ll need to use a full <code>if</code> statement even
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for basic conditions.</p>
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</td>
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<td class="code empty">
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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="switch">Switch</a>.
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</p>
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<p class="footer">
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<a href="https://twitter.com/gobyexample">@gobyexample</a> | <a href="mailto:mmcgrana@gmail.com">feedback</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/if-else">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
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</p>
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