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- <div class="title">boost::hana::embedding< bool > Struct Template Reference<div class="ingroups"><a class="el" href="group__group-core.html">Core</a></div></div> </div>
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- <a name="details" id="details"></a><h2 class="groupheader">Description</h2>
- <div class="textblock"><h3>template<bool = true><br />
- struct boost::hana::embedding< bool ></h3>
- <p>Marks a conversion between data types as being an embedding. </p>
- <p>To mark a conversion between two data types <code>To</code> and <code>From</code> as an embedding, simply use <code>embedding<true></code> (or simply <code>embedding<></code>) as a base class of the corresponding <code>to_impl</code> specialization. If a <code>to_impl</code> specialization does not inherit <code>embedding<true></code> or <code>embedding<></code>, then it is not considered an embedding by the <code><a class="el" href="structboost_1_1hana_1_1is__embedded.html" title="Returns whether a data type can be embedded into another data type.">is_embedded</a></code> metafunction.</p>
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- <h4>Tip</h4>
- <p>The boolean template parameter is useful for marking a conversion as an embedding only when some condition is satisfied. </p>
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- <h2>Example </h2>
- <div class="fragment"><div class="line"><span class="comment">// Copyright Louis Dionne 2013-2017</span></div><div class="line"><span class="comment">// Distributed under the Boost Software License, Version 1.0.</span></div><div class="line"><span class="comment">// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <<a class="code" href="assert_8hpp.html">boost/hana/assert.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="core_2to_8hpp.html">boost/hana/core/to.hpp</a>></span></div><div class="line"><span class="preprocessor">#include <<a class="code" href="core_2when_8hpp.html">boost/hana/core/when.hpp</a>></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <vector></span></div><div class="line"><span class="keyword">namespace </span>hana = <a class="code" href="namespaceboost_1_1hana.html">boost::hana</a>;</div><div class="line"></div><div class="line"></div><div class="line"><span class="keyword">namespace </span>boost { <span class="keyword">namespace </span>hana {</div><div class="line"> <span class="keyword">template</span> <<span class="keyword">typename</span> To, <span class="keyword">typename</span> From></div><div class="line"> <span class="keyword">struct </span>to_impl<std::vector<To>, std::vector<From>,</div><div class="line"> when<is_convertible<From, To>::value>></div><div class="line"> : embedding<is_embedded<From, To>::value></div><div class="line"> {</div><div class="line"> <span class="keyword">static</span> std::vector<To> <a class="code" href="group__group-functional.html#ga30027c383676084be151ef3c6cf2829f">apply</a>(std::vector<From> <span class="keyword">const</span>& xs) {</div><div class="line"> std::vector<To> result;</div><div class="line"> <span class="keywordflow">for</span> (<span class="keyword">auto</span> <span class="keyword">const</span>& x: xs)</div><div class="line"> result.push_back(to<To>(x));</div><div class="line"> <span class="keywordflow">return</span> result;</div><div class="line"> }</div><div class="line"> };</div><div class="line">}}</div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main() {</div><div class="line"> <a class="code" href="group__group-assertions.html#ga4796ae107d58b67e0bbccd5ae6f70101">BOOST_HANA_RUNTIME_CHECK</a>(</div><div class="line"> <a class="code" href="group__group-core.html#gadc70755c1d059139297814fb3bfeb91e">hana::to</a><std::vector<int>>(std::vector<float>{1.1, 2.2, 3.3})</div><div class="line"> ==</div><div class="line"> std::vector<int>{1, 2, 3}</div><div class="line"> );</div><div class="line"></div><div class="line"> static_assert(!hana::is_embedded<std::vector<float>, std::vector<int>>{}, <span class="stringliteral">""</span>);</div><div class="line">}</div></div><!-- fragment --> </div></div><!-- contents -->
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