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random-numbers.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: 随机数</title>
<link rel=stylesheet href="site.css">
</head>
<script>
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<body>
<div class="example" id="random-numbers">
<h2><a href="./">Go by Example 中文版</a>: 随机数</h2>
<table>
<tr>
<td class="docs">
<p>Go 的 <code>math/rand</code> 包提供了<a href="http://en.wikipedia.org/wiki/Pseudorandom_number_generator">伪随机数</a>生成器。</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="https://play.studygolang.com/p/yxt1xJyE1Ae"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kn">import</span> <span class="p">(</span>
<span class="s">"fmt"</span>
<span class="s">"math/rand"</span>
<span class="s">"time"</span>
<span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>例如，<code>rand.Intn</code> 返回一个随机的整数 n，且 <code>0 <= n < 100</code>。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Print</span><span class="p">(</span><span class="nx">rand</span><span class="p">.</span><span class="nf">Intn</span><span class="p">(</span><span class="mi">100</span><span class="p">),</span> <span class="s">","</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Print</span><span class="p">(</span><span class="nx">rand</span><span class="p">.</span><span class="nf">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="nf">Println</span><span class="p">()</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>rand.Float64</code> 返回一个64位浮点数 <code>f</code>，且 <code>0.0 <= f < 1.0</code>。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">rand</span><span class="p">.</span><span class="nf">Float64</span><span class="p">())</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>这个技巧可以用来生成其他范围的随机浮点数，
例如，<code>5.0 <= f < 10.0</code></p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Print</span><span class="p">((</span><span class="nx">rand</span><span class="p">.</span><span class="nf">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">","</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Print</span><span class="p">((</span><span class="nx">rand</span><span class="p">.</span><span class="nf">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="nf">Println</span><span class="p">()</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>默认情况下，给定的种子是确定的，每次都会产生相同的随机数数字序列。
要产生不同的数字序列，需要给定一个不同的种子。
注意，对于想要加密的随机数，使用此方法并不安全，
应该使用 <code>crypto/rand</code>。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">s1</span> <span class="o">:=</span> <span class="nx">rand</span><span class="p">.</span><span class="nf">NewSource</span><span class="p">(</span><span class="nx">time</span><span class="p">.</span><span class="nf">Now</span><span class="p">().</span><span class="nf">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="nf">New</span><span class="p">(</span><span class="nx">s1</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>调用上面返回的 <code>rand.Rand</code>，就像调用 <code>rand</code> 包中函数一样。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Print</span><span class="p">(</span><span class="nx">r1</span><span class="p">.</span><span class="nf">Intn</span><span class="p">(</span><span class="mi">100</span><span class="p">),</span> <span class="s">","</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Print</span><span class="p">(</span><span class="nx">r1</span><span class="p">.</span><span class="nf">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="nf">Println</span><span class="p">()</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>如果使用相同种子生成的随机数生成器，会生成相同的随机数序列。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="nx">s2</span> <span class="o">:=</span> <span class="nx">rand</span><span class="p">.</span><span class="nf">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="nf">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="nf">Print</span><span class="p">(</span><span class="nx">r2</span><span class="p">.</span><span class="nf">Intn</span><span class="p">(</span><span class="mi">100</span><span class="p">),</span> <span class="s">","</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Print</span><span class="p">(</span><span class="nx">r2</span><span class="p">.</span><span class="nf">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="nf">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="nf">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="nf">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="nf">Print</span><span class="p">(</span><span class="nx">r3</span><span class="p">.</span><span class="nf">Intn</span><span class="p">(</span><span class="mi">100</span><span class="p">),</span> <span class="s">","</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Print</span><span class="p">(</span><span class="nx">r3</span><span class="p">.</span><span class="nf">Intn</span><span class="p">(</span><span class="mi">100</span><span class="p">))</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><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>
</td>
</tr>
<tr>
<td class="docs">
<p>有关 Go 提供的其他随机数的信息，
请参阅 <a href="http://golang.org/pkg/math/rand/"><code>math/rand</code></a> 包文档。</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="number-parsing.html">数字解析</a>
</p>
<p class="footer">
<a href="https://twitter.com/mmcgrana">@mmcgrana</a> 和<a href="https://eli.thegreenplace.net">Eli Bendersky</a>编写 | <a href="https://github.com/gobyexample-cn">gobyexample-cn</a> 翻译 | <a href="https://github.com/gobyexample-cn/gobyexample/issues">反馈</a> | <a href="https://github.com/gobyexample-cn/gobyexample">源码</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a> </p>
</p>
</div>
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