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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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<title>Go by Example: Random Numbers</title>
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<div class="example" id="random-numbers">
<h2><a href="./">Go by Example</a>: Random Numbers</h2>
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<p>Go&rsquo;s <code>math/rand</code> package provides
<a href="http://en.wikipedia.org/wiki/Pseudorandom_number_generator">pseudorandom number</a>
generation.</p>
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<a href="http://play.golang.org/p/PGklfJzErTN"><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="p">(</span>
<span class="s">&quot;fmt&quot;</span>
<span class="s">&quot;math/rand&quot;</span>
<span class="s">&quot;time&quot;</span>
<span class="p">)</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>For example, <code>rand.Intn</code> returns a random <code>int</code> n,
<code>0 &lt;= n &lt; 100</code>.</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">Print</span><span class="p">(</span><span class="nx">rand</span><span class="p">.</span><span class="nx">Intn</span><span class="p">(</span><span class="mi">100</span><span class="p">),</span> <span class="s">&quot;,&quot;</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Print</span><span class="p">(</span><span class="nx">rand</span><span class="p">.</span><span class="nx">Intn</span><span class="p">(</span><span class="mi">100</span><span class="p">))</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">()</span>
</pre></div>
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<td class="docs">
<p><code>rand.Float64</code> returns a <code>float64</code> <code>f</code>,
<code>0.0 &lt;= f &lt; 1.0</code>.</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="nx">rand</span><span class="p">.</span><span class="nx">Float64</span><span class="p">())</span>
</pre></div>
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<td class="docs">
<p>This can be used to generate random floats in
other ranges, for example <code>5.0 &lt;= f' &lt; 10.0</code>.</p>
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<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Print</span><span class="p">((</span><span class="nx">rand</span><span class="p">.</span><span class="nx">Float64</span><span class="p">()</span><span class="o">*</span><span class="mi">5</span><span class="p">)</span><span class="o">+</span><span class="mi">5</span><span class="p">,</span> <span class="s">&quot;,&quot;</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Print</span><span class="p">((</span><span class="nx">rand</span><span class="p">.</span><span class="nx">Float64</span><span class="p">()</span> <span class="o">*</span> <span class="mi">5</span><span class="p">)</span> <span class="o">+</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>
</pre></div>
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<td class="docs">
<p>The default number generator is deterministic, so it&rsquo;ll
produce the same sequence of numbers each time by default.
To produce varying sequences, give it a seed that changes.
Note that this is not safe to use for random numbers you
intend to be secret, use <code>crypto/rand</code> for those.</p>
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<div class="highlight"><pre> <span class="nx">s1</span> <span class="o">:=</span> <span class="nx">rand</span><span class="p">.</span><span class="nx">NewSource</span><span class="p">(</span><span class="nx">time</span><span class="p">.</span><span class="nx">Now</span><span class="p">().</span><span class="nx">UnixNano</span><span class="p">())</span>
<span class="nx">r1</span> <span class="o">:=</span> <span class="nx">rand</span><span class="p">.</span><span class="nx">New</span><span class="p">(</span><span class="nx">s1</span><span class="p">)</span>
</pre></div>
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<td class="docs">
<p>Call the resulting <code>rand.Rand</code> just like the
functions on the <code>rand</code> package.</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">Print</span><span class="p">(</span><span class="nx">r1</span><span class="p">.</span><span class="nx">Intn</span><span class="p">(</span><span class="mi">100</span><span class="p">),</span> <span class="s">&quot;,&quot;</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Print</span><span class="p">(</span><span class="nx">r1</span><span class="p">.</span><span class="nx">Intn</span><span class="p">(</span><span class="mi">100</span><span class="p">))</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">()</span>
</pre></div>
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<td class="docs">
<p>If you seed a source with the same number, it
produces the same sequence of random numbers.</p>
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<td class="code">
<div class="highlight"><pre> <span class="nx">s2</span> <span class="o">:=</span> <span class="nx">rand</span><span class="p">.</span><span class="nx">NewSource</span><span class="p">(</span><span class="mi">42</span><span class="p">)</span>
<span class="nx">r2</span> <span class="o">:=</span> <span class="nx">rand</span><span class="p">.</span><span class="nx">New</span><span class="p">(</span><span class="nx">s2</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Print</span><span class="p">(</span><span class="nx">r2</span><span class="p">.</span><span class="nx">Intn</span><span class="p">(</span><span class="mi">100</span><span class="p">),</span> <span class="s">&quot;,&quot;</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Print</span><span class="p">(</span><span class="nx">r2</span><span class="p">.</span><span class="nx">Intn</span><span class="p">(</span><span class="mi">100</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">s3</span> <span class="o">:=</span> <span class="nx">rand</span><span class="p">.</span><span class="nx">NewSource</span><span class="p">(</span><span class="mi">42</span><span class="p">)</span>
<span class="nx">r3</span> <span class="o">:=</span> <span class="nx">rand</span><span class="p">.</span><span class="nx">New</span><span class="p">(</span><span class="nx">s3</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Print</span><span class="p">(</span><span class="nx">r3</span><span class="p">.</span><span class="nx">Intn</span><span class="p">(</span><span class="mi">100</span><span class="p">),</span> <span class="s">&quot;,&quot;</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Print</span><span class="p">(</span><span class="nx">r3</span><span class="p">.</span><span class="nx">Intn</span><span class="p">(</span><span class="mi">100</span><span class="p">))</span>
<span class="p">}</span>
</pre></div>
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<td class="docs">
</td>
<td class="code leading">
<div class="highlight"><pre><span class="gp">$</span> go run random-numbers.go
<span class="go">81,87</span>
<span class="go">0.6645600532184904</span>
<span class="go">7.123187485356329,8.434115364335547</span>
<span class="go">0,28</span>
<span class="go">5,87</span>
<span class="go">5,87</span>
</pre></div>
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<td class="docs">
<p>See the <a href="http://golang.org/pkg/math/rand/"><code>math/rand</code></a>
package docs for references on other random quantities
that Go can provide.</p>
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</td>
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<p class="next">
Next example: <a href="number-parsing">Number Parsing</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/random-numbers">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
</p>
</div>
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