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<title>Go в примерах: Функции коллекции (Collection Functions)</title>
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<div class="example" id="collection-functions">
<h2><a href="./">Go в примерах</a>: Функции коллекции (Collection Functions)</h2>
<table>
<tr>
<td class="docs">
<p>Нам часто нужны наши программы для выполнения операций
с коллекциями данных, таких как выбор всех элементов,
которые удовлетворяют данному предикату, или отображение
всех элементов в новую коллекцию с помощью
пользовательской функции.</p>
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</td>
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<td class="docs">
<p>В некоторых языках идиоматично использовать <a href="http://en.wikipedia.org/wiki/Generic_programming">дженерики</a>
и алгоритмы. Go не поддерживает дженерики; в Go, как
правило, предоставляют функции коллекции если они
необходимы конкретно для вашей программы и ваших
типов данных.</p>
</td>
<td class="code empty leading">
</td>
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<td class="docs">
<p>Вот несколько примеров функций коллекции для срезов
со <code>строковыми значениями</code>. Вы можете использовать эти
примеры, чтобы сделать собственные функции. Обратите
внимание, что в некоторых случаях, возможно, было бы
более явным встроить код, манипулирующий коллекциями,
вместо создания создания вспомогательных функций.</p>
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<td class="code leading">
<a href="http://play.golang.org/p/urAoHQtRHro" target="_blank"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
</pre></div>
</td>
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<td class="docs">
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
<span class="s">&quot;fmt&quot;</span>
<span class="s">&quot;strings&quot;</span>
<span class="p">)</span>
</pre></div>
</td>
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<td class="docs">
<p>Возвращает первый индекс совпадения со строкой <code>t</code> или -1
если совпадение не найдено.</p>
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kd">func</span> <span class="nx">Index</span><span class="p">(</span><span class="nx">vs</span> <span class="p">[]</span><span class="kt">string</span><span class="p">,</span> <span class="nx">t</span> <span class="kt">string</span><span class="p">)</span> <span class="kt">int</span> <span class="p">{</span>
<span class="k">for</span> <span class="nx">i</span><span class="p">,</span> <span class="nx">v</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">vs</span> <span class="p">{</span>
<span class="k">if</span> <span class="nx">v</span> <span class="o">==</span> <span class="nx">t</span> <span class="p">{</span>
<span class="k">return</span> <span class="nx">i</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="k">return</span> <span class="o">-</span><span class="mi">1</span>
<span class="p">}</span>
</pre></div>
</td>
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<td class="docs">
<p>Возвращает <code>true</code> если строка <code>t</code> находится в срезе.</p>
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kd">func</span> <span class="nx">Include</span><span class="p">(</span><span class="nx">vs</span> <span class="p">[]</span><span class="kt">string</span><span class="p">,</span> <span class="nx">t</span> <span class="kt">string</span><span class="p">)</span> <span class="kt">bool</span> <span class="p">{</span>
<span class="k">return</span> <span class="nx">Index</span><span class="p">(</span><span class="nx">vs</span><span class="p">,</span> <span class="nx">t</span><span class="p">)</span> <span class="o">&gt;=</span> <span class="mi">0</span>
<span class="p">}</span>
</pre></div>
</td>
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<td class="docs">
<p>Возвращает <code>true</code> если одна из строк в срезе
удовлетворяет условию <code>f</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kd">func</span> <span class="nx">Any</span><span class="p">(</span><span class="nx">vs</span> <span class="p">[]</span><span class="kt">string</span><span class="p">,</span> <span class="nx">f</span> <span class="kd">func</span><span class="p">(</span><span class="kt">string</span><span class="p">)</span> <span class="kt">bool</span><span class="p">)</span> <span class="kt">bool</span> <span class="p">{</span>
<span class="k">for</span> <span class="nx">_</span><span class="p">,</span> <span class="nx">v</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">vs</span> <span class="p">{</span>
<span class="k">if</span> <span class="nx">f</span><span class="p">(</span><span class="nx">v</span><span class="p">)</span> <span class="p">{</span>
<span class="k">return</span> <span class="kc">true</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="k">return</span> <span class="kc">false</span>
<span class="p">}</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>Возвращает <code>true</code> если все из строк в срезе
удовлетворяют условие <code>f</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kd">func</span> <span class="nx">All</span><span class="p">(</span><span class="nx">vs</span> <span class="p">[]</span><span class="kt">string</span><span class="p">,</span> <span class="nx">f</span> <span class="kd">func</span><span class="p">(</span><span class="kt">string</span><span class="p">)</span> <span class="kt">bool</span><span class="p">)</span> <span class="kt">bool</span> <span class="p">{</span>
<span class="k">for</span> <span class="nx">_</span><span class="p">,</span> <span class="nx">v</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">vs</span> <span class="p">{</span>
<span class="k">if</span> <span class="p">!</span><span class="nx">f</span><span class="p">(</span><span class="nx">v</span><span class="p">)</span> <span class="p">{</span>
<span class="k">return</span> <span class="kc">false</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="k">return</span> <span class="kc">true</span>
<span class="p">}</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>Возвращает новый срез, содержащий все строки в срезе,
которые удовлетворяют условие <code>f</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kd">func</span> <span class="nx">Filter</span><span class="p">(</span><span class="nx">vs</span> <span class="p">[]</span><span class="kt">string</span><span class="p">,</span> <span class="nx">f</span> <span class="kd">func</span><span class="p">(</span><span class="kt">string</span><span class="p">)</span> <span class="kt">bool</span><span class="p">)</span> <span class="p">[]</span><span class="kt">string</span> <span class="p">{</span>
<span class="nx">vsf</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">string</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span>
<span class="k">for</span> <span class="nx">_</span><span class="p">,</span> <span class="nx">v</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">vs</span> <span class="p">{</span>
<span class="k">if</span> <span class="nx">f</span><span class="p">(</span><span class="nx">v</span><span class="p">)</span> <span class="p">{</span>
<span class="nx">vsf</span> <span class="p">=</span> <span class="nb">append</span><span class="p">(</span><span class="nx">vsf</span><span class="p">,</span> <span class="nx">v</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="k">return</span> <span class="nx">vsf</span>
<span class="p">}</span>
</pre></div>
</td>
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<tr>
<td class="docs">
<p>Возвращает новый срез, содержащий результаты выполнения
функции <code>f</code> с каждой строкой исходного слайса.</p>
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kd">func</span> <span class="nx">Map</span><span class="p">(</span><span class="nx">vs</span> <span class="p">[]</span><span class="kt">string</span><span class="p">,</span> <span class="nx">f</span> <span class="kd">func</span><span class="p">(</span><span class="kt">string</span><span class="p">)</span> <span class="kt">string</span><span class="p">)</span> <span class="p">[]</span><span class="kt">string</span> <span class="p">{</span>
<span class="nx">vsm</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">string</span><span class="p">,</span> <span class="nb">len</span><span class="p">(</span><span class="nx">vs</span><span class="p">))</span>
<span class="k">for</span> <span class="nx">i</span><span class="p">,</span> <span class="nx">v</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">vs</span> <span class="p">{</span>
<span class="nx">vsm</span><span class="p">[</span><span class="nx">i</span><span class="p">]</span> <span class="p">=</span> <span class="nx">f</span><span class="p">(</span><span class="nx">v</span><span class="p">)</span>
<span class="p">}</span>
<span class="k">return</span> <span class="nx">vsm</span>
<span class="p">}</span>
</pre></div>
</td>
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<tr>
<td class="docs">
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>Здесь мы пробуем различные функции коллекций.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="kd">var</span> <span class="nx">strs</span> <span class="p">=</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{</span><span class="s">&quot;peach&quot;</span><span class="p">,</span> <span class="s">&quot;apple&quot;</span><span class="p">,</span> <span class="s">&quot;pear&quot;</span><span class="p">,</span> <span class="s">&quot;plum&quot;</span><span class="p">}</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<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">Index</span><span class="p">(</span><span class="nx">strs</span><span class="p">,</span> <span class="s">&quot;pear&quot;</span><span class="p">))</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<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">Include</span><span class="p">(</span><span class="nx">strs</span><span class="p">,</span> <span class="s">&quot;grape&quot;</span><span class="p">))</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<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">Any</span><span class="p">(</span><span class="nx">strs</span><span class="p">,</span> <span class="kd">func</span><span class="p">(</span><span class="nx">v</span> <span class="kt">string</span><span class="p">)</span> <span class="kt">bool</span> <span class="p">{</span>
<span class="k">return</span> <span class="nx">strings</span><span class="p">.</span><span class="nx">HasPrefix</span><span class="p">(</span><span class="nx">v</span><span class="p">,</span> <span class="s">&quot;p&quot;</span><span class="p">)</span>
<span class="p">}))</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<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">All</span><span class="p">(</span><span class="nx">strs</span><span class="p">,</span> <span class="kd">func</span><span class="p">(</span><span class="nx">v</span> <span class="kt">string</span><span class="p">)</span> <span class="kt">bool</span> <span class="p">{</span>
<span class="k">return</span> <span class="nx">strings</span><span class="p">.</span><span class="nx">HasPrefix</span><span class="p">(</span><span class="nx">v</span><span class="p">,</span> <span class="s">&quot;p&quot;</span><span class="p">)</span>
<span class="p">}))</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<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">Filter</span><span class="p">(</span><span class="nx">strs</span><span class="p">,</span> <span class="kd">func</span><span class="p">(</span><span class="nx">v</span> <span class="kt">string</span><span class="p">)</span> <span class="kt">bool</span> <span class="p">{</span>
<span class="k">return</span> <span class="nx">strings</span><span class="p">.</span><span class="nx">Contains</span><span class="p">(</span><span class="nx">v</span><span class="p">,</span> <span class="s">&quot;e&quot;</span><span class="p">)</span>
<span class="p">}))</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>Все примеры, приведенные выше, использовали
анонимные функции, но вы можете использовать именные
функции корректного типа.</p>
</td>
<td class="code leading">
<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">Map</span><span class="p">(</span><span class="nx">strs</span><span class="p">,</span> <span class="nx">strings</span><span class="p">.</span><span class="nx">ToUpper</span><span class="p">))</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code">
<div class="highlight"><pre><span class="p">}</span>
</pre></div>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code">
<div class="highlight"><pre><span class="gp">$</span> go run collection-functions.go
<span class="go">2</span>
<span class="go">false</span>
<span class="go">true</span>
<span class="go">false</span>
<span class="go">[peach apple pear]</span>
<span class="go">[PEACH APPLE PEAR PLUM]</span>
</pre></div>
</td>
</tr>
</table>
<p class="next">
Следующий пример: <a href="string-functions">Строковые функции (String Functions)</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/collection-functions">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
</p>
</div>
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