198 lines
7.4 KiB
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Generated
198 lines
7.4 KiB
Plaintext
Generated
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Go в примерах: Замыкания (Closures)</title>
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<link rel=stylesheet href="site.css">
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<script>
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if (e.key == "ArrowLeft") {
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window.location.href = 'variadic-functions';
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window.location.href = 'recursion';
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<body>
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<div class="example" id="closures">
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<h2><a href="./">Go в примерах</a>: Замыкания (Closures)</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Go поддерживает <a href="http://en.wikipedia.org/wiki/Anonymous_function"><em>анонимные функции</em></a>, которые могут образовывать
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<a href="http://en.wikipedia.org/wiki/Closure_(computer_science)"><em>замыкания</em></a>. Анонимные функции полезны, когда вы хотите
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определить встроенную функцию, не называя ее.</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="http://play.golang.org/p/J2PladF_bU9" 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="s">"fmt"</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>Эта функция intSeq возвращает другую функцию, которую
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мы анонимно определяем в теле intSeq. Возвращенная
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функция присваивается в переменную i, чтобы
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сформировать замыкание.</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">intSeq</span><span class="p">()</span> <span class="kd">func</span><span class="p">()</span> <span class="kt">int</span> <span class="p">{</span>
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<span class="nx">i</span> <span class="o">:=</span> <span class="mi">0</span>
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<span class="k">return</span> <span class="kd">func</span><span class="p">()</span> <span class="kt">int</span> <span class="p">{</span>
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<span class="nx">i</span><span class="o">++</span>
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<span class="k">return</span> <span class="nx">i</span>
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<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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</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>Мы вызываем <code>intSeq</code>, присваивая результат (функцию)
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<code>nextInt</code>. Это значение функции фиксирует свое
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собственное значение <code>i</code>, которое будет обновляться
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каждый раз, когда мы вызываем <code>nextInt</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="nx">nextInt</span> <span class="o">:=</span> <span class="nx">intSeq</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>Посмотрите, что происходит при вызове <code>nextInt</code>
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несколько раз.</p>
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</td>
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<td class="code leading">
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<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">nextInt</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">nextInt</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">nextInt</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>Чтобы подтвердить, что состояние является уникальным
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для этой конкретной функции, создайте и протестируйте
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новую.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="nx">newInts</span> <span class="o">:=</span> <span class="nx">intSeq</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">newInts</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 closures.go
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<span class="go">1</span>
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<span class="go">2</span>
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<span class="go">3</span>
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<span class="go">1</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>Последняя особенность функций, которые мы сейчас
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рассмотрим, - это рекурсия.</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="recursion">Рекурсия (Recursion)</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/closures">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 \"fmt\"\u000A');codeLines.push('func intSeq() func() int {\u000A i := 0\u000A return func() int {\u000A i++\u000A return i\u000A }\u000A}\u000A');codeLines.push('func main() {\u000A');codeLines.push(' nextInt := intSeq()\u000A');codeLines.push(' fmt.Println(nextInt())\u000A fmt.Println(nextInt())\u000A fmt.Println(nextInt())\u000A');codeLines.push(' newInts := intSeq()\u000A fmt.Println(newInts())\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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