215 lines
12 KiB
Plaintext
Generated
215 lines
12 KiB
Plaintext
Generated
<!DOCTYPE html>
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<meta charset="utf-8">
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<title>Go by Example: Random Numbers</title>
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<div class="example" id="random-numbers">
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<h2><a href="./">Go by Example</a>: Random Numbers</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Go’s <code>math/rand/v2</code> package provides
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<a href="https://en.wikipedia.org/wiki/Pseudorandom_number_generator">pseudorandom number</a>
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generation.</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="https://go.dev/play/p/TkgmNAl8euK"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">package</span> <span class="nx">main</span></span></span></code></pre>
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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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<pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">import</span> <span class="p">(</span>
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</span></span><span class="line"><span class="cl"> <span class="s">"fmt"</span>
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</span></span><span class="line"><span class="cl"> <span class="s">"math/rand/v2"</span>
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</span></span><span class="line"><span class="cl"><span class="p">)</span></span></span></code></pre>
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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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<pre class="chroma"><code><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span></span></span></code></pre>
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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>For example, <code>rand.IntN</code> returns a random <code>int</code> n,
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<code>0 <= n < 100</code>.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <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>
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</span></span><span class="line"><span class="cl"> <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>
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</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">()</span></span></span></code></pre>
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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><code>rand.Float64</code> returns a <code>float64</code> <code>f</code>,
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<code>0.0 <= f < 1.0</code>.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <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></span></span></code></pre>
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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>This can be used to generate random floats in
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other ranges, for example <code>5.0 <= f' < 10.0</code>.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <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>
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</span></span><span class="line"><span class="cl"> <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>
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</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">()</span></span></span></code></pre>
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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>If you want a known seed, create a new
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<code>rand.Source</code> and pass it into the <code>New</code>
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constructor. <code>NewPCG</code> creates a new
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<a href="https://en.wikipedia.org/wiki/Permuted_congruential_generator">PCG</a>
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source that requires a seed of two <code>uint64</code>
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numbers.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">s2</span> <span class="o">:=</span> <span class="nx">rand</span><span class="p">.</span><span class="nf">NewPCG</span><span class="p">(</span><span class="mi">42</span><span class="p">,</span> <span class="mi">1024</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"> <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>
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</span></span><span class="line"><span class="cl"> <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>
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</span></span><span class="line"><span class="cl"> <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>
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</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">()</span></span></span></code></pre>
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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">
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<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">s3</span> <span class="o">:=</span> <span class="nx">rand</span><span class="p">.</span><span class="nf">NewPCG</span><span class="p">(</span><span class="mi">42</span><span class="p">,</span> <span class="mi">1024</span><span class="p">)</span>
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</span></span><span class="line"><span class="cl"> <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>
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</span></span><span class="line"><span class="cl"> <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>
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</span></span><span class="line"><span class="cl"> <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>
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</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">()</span>
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</span></span><span class="line"><span class="cl"><span class="p">}</span></span></span></code></pre>
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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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<p>Some of the generated numbers may be
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different when you run the sample.</p>
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</td>
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<td class="code leading">
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<pre class="chroma"><code><span class="line"><span class="cl"><span class="gp">$</span> go run random-numbers.go
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</span></span><span class="line"><span class="cl"><span class="go">68,56
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</span></span></span><span class="line"><span class="cl"><span class="go">0.8090228139659177
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</span></span></span><span class="line"><span class="cl"><span class="go">5.840125017402497,6.937056298890035
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</span></span></span><span class="line"><span class="cl"><span class="go">94,49
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</span></span></span><span class="line"><span class="cl"><span class="go">94,49</span></span></span></code></pre>
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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>See the <a href="https://pkg.go.dev/math/rand/v2"><code>math/rand/v2</code></a>
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package docs for references on other random quantities
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that Go can provide.</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="number-parsing" rel="next">Number Parsing</a>.
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</p>
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<p class="footer">
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Based on
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<em><a href="https://gobyexample.com/">Go by Example</a></em>
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by <a href="https://markmcgranaghan.com">Mark McGranaghan</a>
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and <a href="https://eli.thegreenplace.net">Eli Bendersky</a>,
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licensed under
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<a href="https://creativecommons.org/licenses/by/3.0/">CC BY 3.0</a>.
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<a href="https://git.inkch.xyz/inkch/gobyexample/commit/7123d715f43f2880034db62116a476c01499cae9">
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Style modifications by inkch
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</a>.
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<a href="https://github.com/mmcgrana/gobyexample">Original source</a>.
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</p>
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</div>
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<script>
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var codeLines = [];
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codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"fmt\"\u000A \"math/rand/v2\"\u000A)\u000A');codeLines.push('func main() {\u000A');codeLines.push(' fmt.Print(rand.IntN(100), \",\")\u000A fmt.Print(rand.IntN(100))\u000A fmt.Println()\u000A');codeLines.push(' fmt.Println(rand.Float64())\u000A');codeLines.push(' fmt.Print((rand.Float64()*5)+5, \",\")\u000A fmt.Print((rand.Float64() * 5) + 5)\u000A fmt.Println()\u000A');codeLines.push(' s2 :\u003D rand.NewPCG(42, 1024)\u000A r2 :\u003D rand.New(s2)\u000A fmt.Print(r2.IntN(100), \",\")\u000A fmt.Print(r2.IntN(100))\u000A fmt.Println()\u000A');codeLines.push(' s3 :\u003D rand.NewPCG(42, 1024)\u000A r3 :\u003D rand.New(s3)\u000A fmt.Print(r3.IntN(100), \",\")\u000A fmt.Print(r3.IntN(100))\u000A fmt.Println()\u000A}\u000A');codeLines.push('');codeLines.push('');
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