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gobyexample/public/if-else
Hana 9e216da9ef go.mod: add go.mod and move pygments to third_party 
After go1.16, go will use module mode by default,
even when the repository is checked out under GOPATH
or in a one-off directory. Add go.mod, go.sum to keep
this repo buildable without opting out of the module
mode.

> go mod init github.com/mmcgrana/gobyexample
> go mod tidy
> go mod vendor

In module mode, the 'vendor' directory is special
and its contents will be actively maintained by the
go command. pygments aren't the dependency the go will
know about, so it will delete the contents from vendor
directory. Move it to `third_party` directory now.

And, vendor the blackfriday package.

Note: the tutorial contents are not affected by the
change in go1.16 because all the examples in this
tutorial ask users to run the go command with the
explicit list of files to be compiled (e.g.
`go run hello-world.go` or `go build command-line-arguments.go`).
When the source list is provided, the go command does
not have to compute the build list and whether it's
running in GOPATH mode or module mode becomes irrelevant.
2021-02-15 16:45:26 -05:00

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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example: If/Else</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'for';
}
if (e.key == "ArrowRight") {
window.location.href = 'switch';
}
}
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<body>
<div class="example" id="if-else">
<h2><a href="./">Go by Example</a>: If/Else</h2>
<table>
<tr>
<td class="docs">
<p>Branching with <code>if</code> and <code>else</code> in Go is
straight-forward.</p>
</td>
<td class="code empty leading">
</td>
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</td>
<td class="code leading">
<a href="http://play.golang.org/p/QlMkcwHvmns"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
</pre></div>
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<td class="docs">
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kn">import</span> <span class="s">&quot;fmt&quot;</span>
</pre></div>
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</tr>
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<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>Here&rsquo;s a basic example.</p>
</td>
<td class="code leading">
<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>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;7 is even&quot;</span><span class="p">)</span>
<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;7 is odd&quot;</span><span class="p">)</span>
<span class="p">}</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>You can have an <code>if</code> statement without an else.</p>
</td>
<td class="code leading">
<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>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;8 is divisible by 4&quot;</span><span class="p">)</span>
<span class="p">}</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>A statement can precede conditionals; any variables
declared in this statement are available in all
branches.</p>
</td>
<td class="code leading">
<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">&lt;</span> <span class="mi">0</span> <span class="p">{</span>
<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">&quot;is negative&quot;</span><span class="p">)</span>
<span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="nx">num</span> <span class="p">&lt;</span> <span class="mi">10</span> <span class="p">{</span>
<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">&quot;has 1 digit&quot;</span><span class="p">)</span>
<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
<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">&quot;has multiple digits&quot;</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">}</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>Note that you don&rsquo;t need parentheses around conditions
in Go, but that the braces are required.</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code leading">
<div class="highlight"><pre><span class="gp">$</span> go run <span class="k">if</span>-else.go
<span class="go">7 is odd</span>
<span class="go">8 is divisible by 4</span>
<span class="go">9 has 1 digit</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>There is no <a href="http://en.wikipedia.org/wiki/%3F:">ternary if</a>
in Go, so you&rsquo;ll need to use a full <code>if</code> statement even
for basic conditions.</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
Next example: <a href="switch">Switch</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</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>
</p>
</div>
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