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Oleg Butuzov 646c8b39da bugfix (mmcgrana/gobyexample#294) sha1 sum calculator 
This bugfix implements correct way to calculate source sha1 hash, before it will changed,
by propagation of unchanged sources.

This commit will also include regenerated static files and *.hash files.
2019-10-22 14:27:02 +03:00

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<!DOCTYPE html>
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<title>Go by Example: Slices</title>
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<div class="example" id="slices">
<h2><a href="./">Go by Example</a>: Slices</h2>
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<td class="docs">
<p><em>Slices</em> are a key data type in Go, giving a more
powerful interface to sequences than arrays.</p>
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<td class="code leading">
<a href="http://play.golang.org/p/iLnoIEIxeQ1"><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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<div class="highlight"><pre><span class="kn">import</span> <span class="s">&quot;fmt&quot;</span>
</pre></div>
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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>
</pre></div>
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<td class="docs">
<p>Unlike arrays, slices are typed only by the
elements they contain (not the number of elements).
To create an empty slice with non-zero length, use
the builtin <code>make</code>. Here we make a slice of
<code>string</code>s of length <code>3</code> (initially zero-valued).</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">s</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">string</span><span class="p">,</span> <span class="mi">3</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;emp:&quot;</span><span class="p">,</span> <span class="nx">s</span><span class="p">)</span>
</pre></div>
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<td class="docs">
<p>We can set and get just like with arrays.</p>
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<td class="code leading">
<div class="highlight"><pre> <span class="nx">s</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="p">=</span> <span class="s">&quot;a&quot;</span>
<span class="nx">s</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="p">=</span> <span class="s">&quot;b&quot;</span>
<span class="nx">s</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="p">=</span> <span class="s">&quot;c&quot;</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;set:&quot;</span><span class="p">,</span> <span class="nx">s</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;get:&quot;</span><span class="p">,</span> <span class="nx">s</span><span class="p">[</span><span class="mi">2</span><span class="p">])</span>
</pre></div>
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<td class="docs">
<p><code>len</code> returns the length of the slice as expected.</p>
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<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;len:&quot;</span><span class="p">,</span> <span class="nb">len</span><span class="p">(</span><span class="nx">s</span><span class="p">))</span>
</pre></div>
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<td class="docs">
<p>In addition to these basic operations, slices
support several more that make them richer than
arrays. One is the builtin <code>append</code>, which
returns a slice containing one or more new values.
Note that we need to accept a return value from
<code>append</code> as we may get a new slice value.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">s</span> <span class="p">=</span> <span class="nb">append</span><span class="p">(</span><span class="nx">s</span><span class="p">,</span> <span class="s">&quot;d&quot;</span><span class="p">)</span>
<span class="nx">s</span> <span class="p">=</span> <span class="nb">append</span><span class="p">(</span><span class="nx">s</span><span class="p">,</span> <span class="s">&quot;e&quot;</span><span class="p">,</span> <span class="s">&quot;f&quot;</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;apd:&quot;</span><span class="p">,</span> <span class="nx">s</span><span class="p">)</span>
</pre></div>
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<td class="docs">
<p>Slices can also be <code>copy</code>&rsquo;d. Here we create an
empty slice <code>c</code> of the same length as <code>s</code> and copy
into <code>c</code> from <code>s</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">c</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">string</span><span class="p">,</span> <span class="nb">len</span><span class="p">(</span><span class="nx">s</span><span class="p">))</span>
<span class="nb">copy</span><span class="p">(</span><span class="nx">c</span><span class="p">,</span> <span class="nx">s</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;cpy:&quot;</span><span class="p">,</span> <span class="nx">c</span><span class="p">)</span>
</pre></div>
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<td class="docs">
<p>Slices support a &ldquo;slice&rdquo; operator with the syntax
<code>slice[low:high]</code>. For example, this gets a slice
of the elements <code>s[2]</code>, <code>s[3]</code>, and <code>s[4]</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">l</span> <span class="o">:=</span> <span class="nx">s</span><span class="p">[</span><span class="mi">2</span><span class="p">:</span><span class="mi">5</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;sl1:&quot;</span><span class="p">,</span> <span class="nx">l</span><span class="p">)</span>
</pre></div>
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<td class="docs">
<p>This slices up to (but excluding) <code>s[5]</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">l</span> <span class="p">=</span> <span class="nx">s</span><span class="p">[:</span><span class="mi">5</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;sl2:&quot;</span><span class="p">,</span> <span class="nx">l</span><span class="p">)</span>
</pre></div>
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<td class="docs">
<p>And this slices up from (and including) <code>s[2]</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">l</span> <span class="p">=</span> <span class="nx">s</span><span class="p">[</span><span class="mi">2</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;sl3:&quot;</span><span class="p">,</span> <span class="nx">l</span><span class="p">)</span>
</pre></div>
</td>
</tr>
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<td class="docs">
<p>We can declare and initialize a variable for slice
in a single line as well.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">t</span> <span class="o">:=</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{</span><span class="s">&quot;g&quot;</span><span class="p">,</span> <span class="s">&quot;h&quot;</span><span class="p">,</span> <span class="s">&quot;i&quot;</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;dcl:&quot;</span><span class="p">,</span> <span class="nx">t</span><span class="p">)</span>
</pre></div>
</td>
</tr>
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<td class="docs">
<p>Slices can be composed into multi-dimensional data
structures. The length of the inner slices can
vary, unlike with multi-dimensional arrays.</p>
</td>
<td class="code">
<div class="highlight"><pre> <span class="nx">twoD</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([][]</span><span class="kt">int</span><span class="p">,</span> <span class="mi">3</span><span class="p">)</span>
<span class="k">for</span> <span class="nx">i</span> <span class="o">:=</span> <span class="mi">0</span><span class="p">;</span> <span class="nx">i</span> <span class="p">&lt;</span> <span class="mi">3</span><span class="p">;</span> <span class="nx">i</span><span class="o">++</span> <span class="p">{</span>
<span class="nx">innerLen</span> <span class="o">:=</span> <span class="nx">i</span> <span class="o">+</span> <span class="mi">1</span>
<span class="nx">twoD</span><span class="p">[</span><span class="nx">i</span><span class="p">]</span> <span class="p">=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">int</span><span class="p">,</span> <span class="nx">innerLen</span><span class="p">)</span>
<span class="k">for</span> <span class="nx">j</span> <span class="o">:=</span> <span class="mi">0</span><span class="p">;</span> <span class="nx">j</span> <span class="p">&lt;</span> <span class="nx">innerLen</span><span class="p">;</span> <span class="nx">j</span><span class="o">++</span> <span class="p">{</span>
<span class="nx">twoD</span><span class="p">[</span><span class="nx">i</span><span class="p">][</span><span class="nx">j</span><span class="p">]</span> <span class="p">=</span> <span class="nx">i</span> <span class="o">+</span> <span class="nx">j</span>
<span class="p">}</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;2d: &quot;</span><span class="p">,</span> <span class="nx">twoD</span><span class="p">)</span>
<span class="p">}</span>
</pre></div>
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</table>
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<td class="docs">
<p>Note that while slices are different types than arrays,
they are rendered similarly by <code>fmt.Println</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre><span class="gp">$</span> go run slices.go
<span class="go">emp: [ ]</span>
<span class="go">set: [a b c]</span>
<span class="go">get: c</span>
<span class="go">len: 3</span>
<span class="go">apd: [a b c d e f]</span>
<span class="go">cpy: [a b c d e f]</span>
<span class="go">sl1: [c d e]</span>
<span class="go">sl2: [a b c d e]</span>
<span class="go">sl3: [c d e f]</span>
<span class="go">dcl: [g h i]</span>
<span class="go">2d: [[0] [1 2] [2 3 4]]</span>
</pre></div>
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<td class="docs">
<p>Check out this <a href="http://blog.golang.org/2011/01/go-slices-usage-and-internals.html">great blog post</a>
by the Go team for more details on the design and
implementation of slices in Go.</p>
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<td class="docs">
<p>Now that we&rsquo;ve seen arrays and slices we&rsquo;ll look at
Go&rsquo;s other key builtin data structure: maps.</p>
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<td class="code empty">
</td>
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<p class="next">
Next example: <a href="maps">Maps</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/slices">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
</p>
</div>
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