240 lines
10 KiB
Plaintext
Generated
240 lines
10 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: Карты (Maps)</title>
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<link rel=stylesheet href="site.css">
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</head>
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<script>
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onkeydown = (e) => {
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if (e.key == "ArrowLeft") {
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window.location.href = 'slices';
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}
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if (e.key == "ArrowRight") {
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window.location.href = 'range';
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}
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}
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</script>
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<body>
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<div class="example" id="maps">
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<h2><a href="./">Go в примерах</a>: Карты (Maps)</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Карты - это встроенный <a href="http://en.wikipedia.org/wiki/Associative_array">ассоциативный тип данных</a>
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Go (иногда называемый <em>хешами</em>).</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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<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/HjBZNUEcF_e" 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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</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>Для создания пустой карты, используйте <code>make</code>:
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<code>make(map[key-type]val-type)</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">m</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">map</span><span class="p">[</span><span class="kt">string</span><span class="p">]</span><span class="kt">int</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>Вы можете установить пару ключ/значение
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используя привычный синтаксис <code>name[key] = val</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">m</span><span class="p">[</span><span class="s">"k1"</span><span class="p">]</span> <span class="p">=</span> <span class="mi">7</span>
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<span class="nx">m</span><span class="p">[</span><span class="s">"k2"</span><span class="p">]</span> <span class="p">=</span> <span class="mi">13</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>Вывод карты на экран с помощью <code>fmt.Println</code>
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выведет все пары ключ/значение</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="s">"map:"</span><span class="p">,</span> <span class="nx">m</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>Получить значение по ключу <code>name[key]</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">v1</span> <span class="o">:=</span> <span class="nx">m</span><span class="p">[</span><span class="s">"k1"</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="s">"v1: "</span><span class="p">,</span> <span class="nx">v1</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>Встроенная функция <code>len</code> возвращает количество
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пар ключ/значение для карты.</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="s">"len:"</span><span class="p">,</span> <span class="nb">len</span><span class="p">(</span><span class="nx">m</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>Встроенная функция <code>delete</code> удаляет пару key/value
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из карты.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nb">delete</span><span class="p">(</span><span class="nx">m</span><span class="p">,</span> <span class="s">"k2"</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="s">"map:"</span><span class="p">,</span> <span class="nx">m</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>Необязательное второе возвращаемое значение
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из карты сообщает о том, существовал ли ключ в карте.
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Это может быть использовано для устранения
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неоднозначности между отсутствующими ключами и
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ключами с нулевыми значениями, такими как 0 или
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“”. Здесь нам не нужно само значение, поэтому
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мы проигнорировали его с пустым идентификатором _.</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">_</span><span class="p">,</span> <span class="nx">prs</span> <span class="o">:=</span> <span class="nx">m</span><span class="p">[</span><span class="s">"k2"</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="s">"prs:"</span><span class="p">,</span> <span class="nx">prs</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>Вы можете объявить и наполнить карту в одной
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строке с помощью подобного синтаксиса.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="nx">n</span> <span class="o">:=</span> <span class="kd">map</span><span class="p">[</span><span class="kt">string</span><span class="p">]</span><span class="kt">int</span><span class="p">{</span><span class="s">"foo"</span><span class="p">:</span> <span class="mi">1</span><span class="p">,</span> <span class="s">"bar"</span><span class="p">:</span> <span class="mi">2</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="s">"map:"</span><span class="p">,</span> <span class="nx">n</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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<p>Обратите внимание, что карты отображаются в виде
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<code>map[k:v k:v]</code>при печати с помощью <code>fmt.Println</code></p>
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</td>
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<td class="code">
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<div class="highlight"><pre><span class="gp">$</span> go run maps.go
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<span class="go">map: map[k1:7 k2:13]</span>
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<span class="go">v1: 7</span>
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<span class="go">len: 2</span>
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<span class="go">map: map[k1:7]</span>
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<span class="go">prs: false</span>
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<span class="go">map: map[bar:2 foo:1]</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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<p class="next">
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Следующий пример: <a href="range">Ряд (Range)</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/maps">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 main() {\u000A');codeLines.push(' m := make(map[string]int)\u000A');codeLines.push(' m[\"k1\"] = 7\u000A m[\"k2\"] = 13\u000A');codeLines.push(' fmt.Println(\"map:\", m)\u000A');codeLines.push(' v1 := m[\"k1\"]\u000A fmt.Println(\"v1: \", v1)\u000A');codeLines.push(' fmt.Println(\"len:\", len(m))\u000A');codeLines.push(' delete(m, \"k2\")\u000A fmt.Println(\"map:\", m)\u000A');codeLines.push(' _, prs := m[\"k2\"]\u000A fmt.Println(\"prs:\", prs)\u000A');codeLines.push(' n := map[string]int{\"foo\": 1, \"bar\": 2}\u000A fmt.Println(\"map:\", n)\u000A}\u000A');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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