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  26 <a name="boost.compute.field"></a><div class="titlepage"></div>
  27 <div class="refnamediv">
  28 <h2><span class="refentrytitle">Class template field</span></h2>
  29 <p>boost::compute::field</p>
  30 </div>
  31 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
  32 <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../boost_compute/reference.html#header.boost.compute.functional.field_hpp" title="Header &lt;boost/compute/functional/field.hpp&gt;">boost/compute/functional/field.hpp</a>&gt;
  33
  34 </span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span>
  35 <span class="keyword">class</span> <a class="link" href="field.html" title="Class template field">field</a> <span class="special">{</span>
  36 <span class="keyword">public</span><span class="special">:</span>
  37   <span class="comment">// types</span>
  38   <span class="keyword">typedef</span> <span class="identifier">T</span> <a name="boost.compute.field.result_type"></a><span class="identifier">result_type</span><span class="special">;</span>  <span class="comment">// Result type. </span>
  39
  40   <span class="comment">// <a class="link" href="field.html#boost.compute.fieldconstruct-copy-destruct">construct/copy/destruct</a></span>
  41   <a class="link" href="field.html#idm46009692886640-bb"><span class="identifier">field</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  42 <span class="special">}</span><span class="special">;</span></pre></div>
  43 <div class="refsect1">
  44 <a name="idm46113322644752"></a><h2>Description</h2>
  45 <p>Returns the named field from a value.</p>
  46 <p>The template-type <code class="computeroutput">T</code> specifies the field's value type. Note that the value type must match the actual type of the field otherwise runtime compilation or logic errors may occur.</p>
  47 <p>For example, to access the <code class="computeroutput">second</code> field in a <code class="computeroutput">std::pair&lt;int, float&gt;</code> object: </p>
  48 <pre class="programlisting"><span class="identifier">field</span><span class="special">&lt;</span><span class="keyword">float</span><span class="special">&gt;</span><span class="special">(</span><span class="string">"second"</span><span class="special">)</span><span class="special">;</span>
  49 </pre>
  50 <p>This can also be used with vector types to access individual components as well as perform swizzle operations.</p>
  51 <p>For example, to access the first and third components of an <code class="computeroutput">int</code> vector type (e.g. <code class="computeroutput">int4</code>): </p>
  52 <pre class="programlisting"><span class="identifier">field</span><span class="special">&lt;</span><span class="identifier">int2_</span><span class="special">&gt;</span><span class="special">(</span><span class="string">"xz"</span><span class="special">)</span><span class="special">;</span>
  53 </pre>
  54 <p><span class="bold"><strong>See Also:</strong></span></p>
  55 <p><a class="link" href="get.html" title="Struct template get">get&lt;N&gt;</a> </p>
  56 <p>
  57 </p>
  58 <p>
  59 </p>
  60 <div class="refsect2">
  61 <a name="idm46113322627168"></a><h3>
  62 <a name="boost.compute.fieldconstruct-copy-destruct"></a><code class="computeroutput">field</code>
  63         public
  64        construct/copy/destruct</h3>
  65 <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
  66 <pre class="literallayout"><a name="idm46009692886640-bb"></a><span class="identifier">field</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&amp;</span> field<span class="special">)</span><span class="special">;</span></pre>Creates a new field functor with <code class="computeroutput">field</code>. </li></ol></div>
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  72 <td align="right"><div class="copyright-footer">Copyright &#169; 2013, 2014 Kyle Lutz<p>
  73         Distributed under the Boost Software License, Version 1.0. (See accompanying
  74         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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