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<div class="title">W:/Work/Software/Libraries/utl/include/utl/meta/detection.h</div>  </div>
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<div class="contents">
<p>detection interface</p>
<p>Checks if Op&lt;Args...&gt; is a valid expression without evaluating it.</p>
<dl class="tparams"><dt>Template Parameters</dt><dd>
  <table class="tparams">
    <tr><td class="paramname">Op</td><td>a meta-callback function to pass Args... </td></tr>
    <tr><td class="paramname">Args...</td><td>types to pass to Op for checking </td></tr>
  </table>
  </dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>status of the operation [bool_] <ul>
<li>true_ if Op&lt;Args...&gt; is valid expression </li>
<li>false_ if Op&lt;Args...&gt; is not valid</li>
</ul>
<div class="fragment"><div class="line"><span class="comment">// archetypal alias for a copy assignment operation</span></div><div class="line"><span class="keyword">template</span>&lt; <span class="keyword">class</span> T &gt; <span class="keyword">using</span> copy_assign_t = decltype( declval&lt;T&amp;&gt;() = declval&lt;T const &amp;&gt;() );</div><div class="line"></div><div class="line"><span class="keyword">template</span>&lt; <span class="keyword">class</span> T &gt; <span class="keyword">using</span> is_copy_assignable = is_detected&lt; copy_assign_t, T &gt;;</div></div><!-- fragment --></dd></dl>
<div class="fragment"><div class="line"></div><div class="line"><span class="preprocessor">#ifndef __utl_meta_detection_h__</span></div><div class="line"><span class="preprocessor">#define __utl_meta_detection_h__</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="impl_8h.html">utl/core/impl.h</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="operations_8h.html">utl/meta/operations.h</a>&gt;</span></div><div class="line"><span class="preprocessor">#include &lt;type_traits&gt;</span></div><div class="line"></div><div class="line"></div><div class="line"><span class="keyword">namespace </span><a class="code" href="namespaceutl.html">utl</a> {</div><div class="line"><span class="keyword">namespace </span>meta {</div><div class="line"></div><div class="line"><span class="preprocessor">   #if defined(UTL_WORKAROUND_CWG_1558)</span></div><div class="line">      <span class="keyword">template</span>&lt;<span class="keyword">typename</span>... _Ts&gt;</div><div class="line">      <span class="keyword">struct </span><a name="a0"></a><a class="code" href="group__detection.html#gac16d50de47cf57734433e9ea636522c5">void_</a> {</div><div class="line">         <span class="keyword">using</span> type = void;</div><div class="line">      };</div><div class="line">      <span class="keyword">template</span>&lt;<span class="keyword">typename</span>... _Ts&gt;</div><div class="line">      <span class="keyword">using</span> <a name="a1"></a><a class="code" href="group__detection.html#gae7373c997420d16cf37e542eb3cfa3ad">void_t</a> = <a name="a2"></a><a class="code" href="namespaceutl_1_1meta.html#aa5a37adba244ff4286f994111c4c02ea">eval</a>&lt;<a class="code" href="group__detection.html#gac16d50de47cf57734433e9ea636522c5">void_</a>&lt;_Ts...&gt;&gt;;</div><div class="line"><span class="preprocessor">   #else</span></div><div class="line">      <span class="keyword">template</span> &lt;<span class="keyword">typename</span>...&gt; <span class="keyword">using</span> <a class="code" href="group__detection.html#gac16d50de47cf57734433e9ea636522c5">void_</a>  = void;</div><div class="line">      <span class="keyword">template</span> &lt;<span class="keyword">typename</span>...&gt; <span class="keyword">using</span> <a class="code" href="group__detection.html#gae7373c997420d16cf37e542eb3cfa3ad">void_t</a> = void;</div><div class="line"><span class="preprocessor">   #endif</span></div><div class="line"></div><div class="line">   <span class="keyword">struct </span>nat_ {</div><div class="line">      nat_()  = <span class="keyword">delete</span>;</div><div class="line">      ~nat_() = <span class="keyword">delete</span>;</div><div class="line">      nat_(nat_ <span class="keyword">const</span>&amp;)         = <span class="keyword">delete</span>;</div><div class="line">      <span class="keywordtype">void</span> operator = (nat_ <span class="keyword">const</span>&amp;) = <span class="keyword">delete</span>;</div><div class="line">   };</div><div class="line"></div><div class="line">   <span class="keyword">namespace </span>detail {</div><div class="line">      <span class="keyword">template</span> &lt;<span class="keyword">typename</span> Default,</div><div class="line">                <span class="keyword">typename</span> AlwaysVoid,</div><div class="line">                <span class="keyword">template</span>&lt;<span class="keyword">typename</span>...&gt; <span class="keyword">class </span>Op, <span class="keyword">typename</span>... Args&gt;</div><div class="line">      <span class="keyword">struct </span>detector {</div><div class="line">         <span class="keyword">using</span> detected = <a name="a3"></a><a class="code" href="namespaceutl_1_1meta.html#a55511dbaa0adb605ce22dcec11f8d22d">false_</a>;</div><div class="line">         <span class="keyword">using</span> type = Default;</div><div class="line">      };</div><div class="line"></div><div class="line">      <span class="keyword">template</span> &lt;<span class="keyword">typename</span> Default,</div><div class="line">                <span class="keyword">template</span>&lt;<span class="keyword">typename</span>...&gt; <span class="keyword">class </span>Op, <span class="keyword">typename</span>... Args&gt;</div><div class="line">      <span class="keyword">struct </span>detector &lt;Default, <a class="code" href="group__detection.html#gae7373c997420d16cf37e542eb3cfa3ad">void_t</a>&lt;Op&lt;Args...&gt;&gt;, Op, Args...&gt; {</div><div class="line">         <span class="keyword">using</span> detected = <a name="a4"></a><a class="code" href="namespaceutl_1_1meta.html#ae9a5a8fbe8202785f059935af219fb97">true_</a>;</div><div class="line">         <span class="keyword">using</span> type = Op&lt;Args...&gt;;</div><div class="line">      };</div><div class="line"></div><div class="line">      <span class="keyword">template</span> &lt;<span class="keyword">typename</span> Default,</div><div class="line">                <span class="keyword">template</span>&lt;<span class="keyword">typename</span>...&gt; <span class="keyword">class </span>Op, <span class="keyword">typename</span>... Args&gt;</div><div class="line">      <span class="keyword">using</span> <a name="a5"></a><a class="code" href="namespaceutl_1_1meta_1_1detail.html#a835827cb3116483228d6f7f774b68970">detected_or</a> = detector&lt;Default, void, Op, Args...&gt;;</div><div class="line">   } <span class="comment">// namespace detail</span></div><div class="line"><span class="comment"></span></div><div class="line"></div><div class="line">   <span class="keyword">template</span> &lt;<span class="keyword">template</span>&lt;<span class="keyword">typename</span>...&gt; <span class="keyword">class </span>Op, <span class="keyword">typename</span>... Args&gt;</div><div class="line">   <span class="keyword">using</span> <a name="a6"></a><a class="code" href="namespaceutl_1_1meta.html#a5329219a9d2f195421a78d8e07873507">is_detected</a> = <span class="keyword">typename</span> detail::detector&lt;nat_, void, Op, Args...&gt;::detected;</div><div class="line"></div><div class="line">   <span class="keyword">template</span>&lt; <span class="keyword">template</span>&lt;<span class="keyword">typename</span>...&gt; <span class="keyword">class </span>Op, <span class="keyword">typename</span>... Args&gt;</div><div class="line">   constexpr <span class="keywordtype">bool</span> <a name="a7"></a><a class="code" href="namespaceutl_1_1meta.html#a4f3184ccb8e8ba2a78e2d2e83a0b9885">is_detected_v</a> = <a class="code" href="namespaceutl_1_1meta.html#a5329219a9d2f195421a78d8e07873507">is_detected</a>&lt;Op, Args...&gt;::value;</div><div class="line"></div><div class="line">   <span class="keyword">template</span> &lt;<span class="keyword">template</span>&lt;<span class="keyword">typename</span>...&gt; <span class="keyword">class </span>Op, <span class="keyword">typename</span>... Args&gt;</div><div class="line">   <span class="keyword">using</span> <a name="a8"></a><a class="code" href="namespaceutl_1_1meta.html#aa654a286b3bc8e6d8116ee1f57087110">detected_t</a> = <a class="code" href="namespaceutl_1_1meta.html#aa5a37adba244ff4286f994111c4c02ea">eval</a> &lt;</div><div class="line">      detail::detector&lt;nat_, void, Op, Args...&gt;</div><div class="line">   &gt;;</div><div class="line"></div><div class="line">   <span class="keyword">template</span> &lt;<span class="keyword">typename</span> Default,</div><div class="line">             <span class="keyword">template</span>&lt;<span class="keyword">typename</span>...&gt; <span class="keyword">class </span>Op, <span class="keyword">typename</span>... Args&gt;</div><div class="line">   <span class="keyword">using</span> <a name="a9"></a><a class="code" href="namespaceutl_1_1meta.html#a8fd055bc6c6c3b1d551e9605aa35644c">detected_or_t</a> = <a class="code" href="namespaceutl_1_1meta.html#aa5a37adba244ff4286f994111c4c02ea">eval</a> &lt;</div><div class="line">      <a class="code" href="namespaceutl_1_1meta_1_1detail.html#a835827cb3116483228d6f7f774b68970">detail::detected_or</a>&lt;Default, Op, Args...&gt;</div><div class="line">   &gt;;</div><div class="line"></div><div class="line">   <span class="keyword">template</span> &lt;<span class="keyword">typename</span> Expected,</div><div class="line">             <span class="keyword">template</span>&lt;<span class="keyword">typename</span>...&gt; <span class="keyword">class </span>Op, <span class="keyword">typename</span>... Args &gt;</div><div class="line">   <span class="keyword">using</span> <a name="a10"></a><a class="code" href="namespaceutl_1_1meta.html#ad5224ef66e8f40efaaf3ad3d605dd629">is_detected_exact</a> = <a class="code" href="namespaceutl_1_1meta.html#aa5a37adba244ff4286f994111c4c02ea">eval</a> &lt;</div><div class="line">      same_&lt;Expected, <a class="code" href="namespaceutl_1_1meta.html#aa654a286b3bc8e6d8116ee1f57087110">detected_t</a>&lt;Op, Args...&gt;&gt;</div><div class="line">   &gt;;</div><div class="line"></div><div class="line">   <span class="keyword">template</span> &lt;<span class="keyword">typename</span> Expected,</div><div class="line">             <span class="keyword">template</span>&lt;<span class="keyword">typename</span>...&gt; <span class="keyword">class </span>Op, <span class="keyword">typename</span>... Args &gt;</div><div class="line">   constexpr <span class="keywordtype">bool</span> <a name="a11"></a><a class="code" href="namespaceutl_1_1meta.html#a960827a1d72083a511f8ea4ccc8beceb">is_detected_exact_v</a> = <a class="code" href="namespaceutl_1_1meta.html#ad5224ef66e8f40efaaf3ad3d605dd629">is_detected_exact</a>&lt; Expected, Op, Args...&gt;::value;</div><div class="line"></div><div class="line">   <span class="keyword">template</span> &lt;<span class="keyword">typename</span> To,</div><div class="line">             <span class="keyword">template</span>&lt;<span class="keyword">typename</span>...&gt; <span class="keyword">class </span>Op, <span class="keyword">typename</span>... Args &gt;</div><div class="line">   <span class="keyword">using</span> <a name="a12"></a><a class="code" href="namespaceutl_1_1meta.html#afa24702fa15a1d0a8a05761c54b79def">is_detected_convertible</a> = <a class="code" href="namespaceutl_1_1meta.html#aa5a37adba244ff4286f994111c4c02ea">eval</a> &lt;</div><div class="line">      std::is_convertible&lt; <a class="code" href="namespaceutl_1_1meta.html#aa654a286b3bc8e6d8116ee1f57087110">detected_t</a>&lt;Op, Args...&gt;, To &gt;</div><div class="line">   &gt;;</div><div class="line"></div><div class="line">   <span class="keyword">template</span> &lt;<span class="keyword">typename</span> To,</div><div class="line">             <span class="keyword">template</span>&lt;<span class="keyword">typename</span>...&gt; <span class="keyword">class </span>Op, <span class="keyword">typename</span>... Args &gt;</div><div class="line">   constexpr <span class="keywordtype">bool</span> <a name="a13"></a><a class="code" href="namespaceutl_1_1meta.html#acba521b528e775be4b37d2e481e0f138">is_detected_convertible_v</a> =</div><div class="line">      <a class="code" href="namespaceutl_1_1meta.html#afa24702fa15a1d0a8a05761c54b79def">is_detected_convertible</a>&lt;To, Op, Args...&gt;::value;</div><div class="line"></div><div class="line">}}</div><div class="line"></div><div class="line"><span class="preprocessor">#endif </span><span class="comment">/* __utl_meta_detection_h__ */</span><span class="preprocessor"></span></div></div><!-- fragment --> </div><!-- contents -->
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