243 lines
11 KiB
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243 lines
11 KiB
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<!DOCTYPE html>
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<html>
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<meta charset="utf-8">
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<title>Go в примерах: Интерфейсы (Interfaces)</title>
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<div class="example" id="interfaces">
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<h2><a href="./">Go в примерах</a>: Интерфейсы (Interfaces)</h2>
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<table>
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<tr>
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<td class="docs">
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<p><em>Интерфейсы</em> это коллекции методов.</p>
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<td class="code empty leading">
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</td>
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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="http://play.golang.org/p/bS2bkTzP8cG" target="_blank"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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</pre></div>
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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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<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
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<span class="s">"fmt"</span>
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<span class="s">"math"</span>
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<span class="p">)</span>
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</pre></div>
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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>Пример базового интерфейса в Go</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">type</span> <span class="nx">geometry</span> <span class="kd">interface</span> <span class="p">{</span>
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<span class="nx">area</span><span class="p">()</span> <span class="kt">float64</span>
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<span class="nx">perim</span><span class="p">()</span> <span class="kt">float64</span>
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<span class="p">}</span>
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</pre></div>
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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>В нашем примере мы будем реализовывать этот интерфейс
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для типов <code>rect</code> и <code>circle</code>.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">type</span> <span class="nx">rect</span> <span class="kd">struct</span> <span class="p">{</span>
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<span class="nx">width</span><span class="p">,</span> <span class="nx">height</span> <span class="kt">float64</span>
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<span class="p">}</span>
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<span class="kd">type</span> <span class="nx">circle</span> <span class="kd">struct</span> <span class="p">{</span>
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<span class="nx">radius</span> <span class="kt">float64</span>
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<span class="p">}</span>
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</pre></div>
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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>Чтобы реализовать интерфейс на Go, нам просто нужно
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реализовать все методы в интерфейсе. Здесь мы
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реализуем интерфейс <code>geometry</code> для <code>rect</code>.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="p">(</span><span class="nx">r</span> <span class="nx">rect</span><span class="p">)</span> <span class="nx">area</span><span class="p">()</span> <span class="kt">float64</span> <span class="p">{</span>
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<span class="k">return</span> <span class="nx">r</span><span class="p">.</span><span class="nx">width</span> <span class="o">*</span> <span class="nx">r</span><span class="p">.</span><span class="nx">height</span>
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<span class="p">}</span>
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<span class="kd">func</span> <span class="p">(</span><span class="nx">r</span> <span class="nx">rect</span><span class="p">)</span> <span class="nx">perim</span><span class="p">()</span> <span class="kt">float64</span> <span class="p">{</span>
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<span class="k">return</span> <span class="mi">2</span><span class="o">*</span><span class="nx">r</span><span class="p">.</span><span class="nx">width</span> <span class="o">+</span> <span class="mi">2</span><span class="o">*</span><span class="nx">r</span><span class="p">.</span><span class="nx">height</span>
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<span class="p">}</span>
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</pre></div>
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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>Реализация для <code>circle</code>.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="p">(</span><span class="nx">c</span> <span class="nx">circle</span><span class="p">)</span> <span class="nx">area</span><span class="p">()</span> <span class="kt">float64</span> <span class="p">{</span>
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<span class="k">return</span> <span class="nx">math</span><span class="p">.</span><span class="nx">Pi</span> <span class="o">*</span> <span class="nx">c</span><span class="p">.</span><span class="nx">radius</span> <span class="o">*</span> <span class="nx">c</span><span class="p">.</span><span class="nx">radius</span>
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<span class="p">}</span>
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<span class="kd">func</span> <span class="p">(</span><span class="nx">c</span> <span class="nx">circle</span><span class="p">)</span> <span class="nx">perim</span><span class="p">()</span> <span class="kt">float64</span> <span class="p">{</span>
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<span class="k">return</span> <span class="mi">2</span> <span class="o">*</span> <span class="nx">math</span><span class="p">.</span><span class="nx">Pi</span> <span class="o">*</span> <span class="nx">c</span><span class="p">.</span><span class="nx">radius</span>
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<span class="p">}</span>
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</pre></div>
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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>Если переменная реализует интерфейс, то мы можем
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вызывать методы, которые находятся в этом интерфейсе.
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Функция <code>measure</code> использует это преимущество, для
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работы с любой фигурой.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">measure</span><span class="p">(</span><span class="nx">g</span> <span class="nx">geometry</span><span class="p">)</span> <span class="p">{</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">g</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">g</span><span class="p">.</span><span class="nx">area</span><span class="p">())</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">g</span><span class="p">.</span><span class="nx">perim</span><span class="p">())</span>
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<span class="p">}</span>
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</pre></div>
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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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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
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<span class="nx">r</span> <span class="o">:=</span> <span class="nx">rect</span><span class="p">{</span><span class="nx">width</span><span class="p">:</span> <span class="mi">3</span><span class="p">,</span> <span class="nx">height</span><span class="p">:</span> <span class="mi">4</span><span class="p">}</span>
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<span class="nx">c</span> <span class="o">:=</span> <span class="nx">circle</span><span class="p">{</span><span class="nx">radius</span><span class="p">:</span> <span class="mi">5</span><span class="p">}</span>
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</pre></div>
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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>Типы <code>circle</code> и <code>rect</code> структур реализуют
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интерфейс <code>geometry</code>, поэтому мы можем использовать
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экземпляры этих структур в качестве аргументов для
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<code>measure</code>.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="nx">measure</span><span class="p">(</span><span class="nx">r</span><span class="p">)</span>
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<span class="nx">measure</span><span class="p">(</span><span class="nx">c</span><span class="p">)</span>
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<span class="p">}</span>
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</pre></div>
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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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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="gp">$</span> go run interfaces.go
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<span class="go">{3 4}</span>
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<span class="go">12</span>
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<span class="go">14</span>
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<span class="go">{5}</span>
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<span class="go">78.53981633974483</span>
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<span class="go">31.41592653589793</span>
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</pre></div>
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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>Чтобы узнать больше об интерфейсах Go, ознакомьтесь с
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<a href="http://jordanorelli.tumblr.com/post/32665860244/how-to-use-interfaces-in-go">этой статьей</a>.</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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Следующий пример: <a href="errors">Ошибки (Errors)</a>.
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</p>
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<p class="footer">
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by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/interfaces">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</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\"\u000A)\u000A');codeLines.push('type geometry interface {\u000A area() float64\u000A perim() float64\u000A}\u000A');codeLines.push('type rect struct {\u000A width, height float64\u000A}\u000Atype circle struct {\u000A radius float64\u000A}\u000A');codeLines.push('func (r rect) area() float64 {\u000A return r.width * r.height\u000A}\u000Afunc (r rect) perim() float64 {\u000A return 2*r.width + 2*r.height\u000A}\u000A');codeLines.push('func (c circle) area() float64 {\u000A return math.Pi * c.radius * c.radius\u000A}\u000Afunc (c circle) perim() float64 {\u000A return 2 * math.Pi * c.radius\u000A}\u000A');codeLines.push('func measure(g geometry) {\u000A fmt.Println(g)\u000A fmt.Println(g.area())\u000A fmt.Println(g.perim())\u000A}\u000A');codeLines.push('func main() {\u000A r := rect{width: 3, height: 4}\u000A c := circle{radius: 5}\u000A');codeLines.push(' measure(r)\u000A measure(c)\u000A}\u000A');codeLines.push('');codeLines.push('');
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</script>
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<script src="site.js" async></script>
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</body>
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</html>
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