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<h1 class="refname">Ds\Sequence::reduce</h1>
<p class="verinfo">(PECL ds >= 1.0.0)</p><p class="refpurpose"><span class="refname">Ds\Sequence::reduce</span> — <span class="dc-title">Reduces the sequence to a single value using a callback function</span></p>
</div>
<div class="refsect1 description" id="refsect1-ds-sequence.reduce-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="modifier">abstract</span> <span class="modifier">public</span> <span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <span class="methodname"><strong>Ds\Sequence::reduce</strong></span>
( <span class="methodparam"><span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span> <code class="parameter">$callback</code></span>
[, <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$initial</code></span>
] )</div>
<p class="para rdfs-comment">
Reduces the sequence to a single value using a callback function.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-ds-sequence.reduce-parameters">
<h3 class="title">Parameters</h3>
<dl>
<dt>
<code class="parameter">callback</code></dt>
<dd>
<div class="methodsynopsis dc-description">
<span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <span class="methodname"><span class="replaceable">callback</span></span>
( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$carry</code></span>
, <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$value</code></span>
)</div>
<dl>
<dt>
<code class="parameter">carry</code></dt>
<dd>
<p class="para">
The return value of the previous callback, or <code class="parameter">initial</code> if
it's the first iteration.
</p>
</dd>
<dt>
<code class="parameter">value</code></dt>
<dd>
<p class="para">
The value of the current iteration.
</p>
</dd>
</dl>
</dd>
<dt>
<code class="parameter">initial</code></dt>
<dd>
<p class="para">
The initial value of the carry value. Can be <strong><code>NULL</code></strong>.
</p>
</dd>
</dl>
</div>
<div class="refsect1 returnvalues" id="refsect1-ds-sequence.reduce-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
The return value of the final callback.
</p>
</div>
<div class="refsect1 examples" id="refsect1-ds-sequence.reduce-examples">
<h3 class="title">Examples</h3>
<div class="example" id="example-5152">
<p><strong>Example #1 <span class="function"><strong>Ds\Sequence::reduce()</strong></span> with initial value example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$sequence </span><span style="color: #007700">= new \</span><span style="color: #0000BB">Ds</span><span style="color: #007700">\</span><span style="color: #0000BB">Vector</span><span style="color: #007700">([</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">3</span><span style="color: #007700">]);<br /><br /></span><span style="color: #0000BB">$callback </span><span style="color: #007700">= function(</span><span style="color: #0000BB">$carry</span><span style="color: #007700">, </span><span style="color: #0000BB">$value</span><span style="color: #007700">) {<br /> return </span><span style="color: #0000BB">$carry </span><span style="color: #007700">* </span><span style="color: #0000BB">$value</span><span style="color: #007700">;<br />};<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$sequence</span><span style="color: #007700">-></span><span style="color: #0000BB">reduce</span><span style="color: #007700">(</span><span style="color: #0000BB">$callback</span><span style="color: #007700">, </span><span style="color: #0000BB">5</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">// Iterations:<br />//<br />// $carry = $initial = 5<br />//<br />// $carry = $carry * 1 = 5<br />// $carry = $carry * 2 = 10<br />// $carry = $carry * 3 = 30<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output
something similar to:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
int(30)
</pre></div>
</div>
</div>
<div class="example" id="example-5153">
<p><strong>Example #2 <span class="function"><strong>Ds\Sequence::reduce()</strong></span> without an initial value example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$sequence </span><span style="color: #007700">= new \</span><span style="color: #0000BB">Ds</span><span style="color: #007700">\</span><span style="color: #0000BB">Vector</span><span style="color: #007700">([</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">3</span><span style="color: #007700">]);<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$sequence</span><span style="color: #007700">-></span><span style="color: #0000BB">reduce</span><span style="color: #007700">(function(</span><span style="color: #0000BB">$carry</span><span style="color: #007700">, </span><span style="color: #0000BB">$value</span><span style="color: #007700">) {<br /> return </span><span style="color: #0000BB">$carry </span><span style="color: #007700">+ </span><span style="color: #0000BB">$value </span><span style="color: #007700">+ </span><span style="color: #0000BB">5</span><span style="color: #007700">;<br />}));<br /><br /></span><span style="color: #FF8000">// Iterations:<br />//<br />// $carry = $initial = null<br />//<br />// $carry = $carry + 1 + 5 = 6<br />// $carry = $carry + 2 + 5 = 13<br />// $carry = $carry + 3 + 5 = 21<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output
something similar to:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
int(21)
</pre></div>
</div>
</div>
</div>
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