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  3. <title>Constexpr domain source - Boost.Outcome documentation</title>
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  13.   <div class="titlepage"><div><div><h1 style="clear: both">Constexpr domain source</h1></div></div></div>
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  14.   <p>Back in <a href="../../experimental/worked-example/constructor.html">The constructor</a>, we
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  15. declared but did not implement a <code>.get()</code> function which returns a constexpr static
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  16. instance of the domain. We implement this now:</p>
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  17. 

  18. <div class="code-snippet"><div class="highlight"><pre class="chroma"><code class="language-c++" data-lang="c++"><span class="c1">// 100% constexpr instantiation
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  19. </span><span class="c1"></span><span class="k">constexpr</span> <span class="n">_file_io_error_domain</span> <span class="n">file_io_error_domain</span><span class="p">;</span>
    20. 

  20. <span class="kr">inline</span> <span class="k">constexpr</span> <span class="k">const</span> <span class="n">_file_io_error_domain</span> <span class="o">&amp;</span><span class="n">_file_io_error_domain</span><span class="o">::</span><span class="n">get</span><span class="p">()</span>
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  21. <span class="p">{</span>
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  22.   <span class="k">return</span> <span class="n">file_io_error_domain</span><span class="p">;</span>
    23. 

  23. <span class="p">}</span>
    24. 

  24. </code></pre></div><a href="https://github.com/boostorg/outcome/tree/master/doc/src/snippets/experimental_status_code.cpp#L142" class="code-snippet-url" target="_blank">View this code on Github</a></div>
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  25. 

  26. 

  27. <p>As this is 100% constexpr, it can be (and is under optimisation) implemented entirely
    28. 

  28. in the mind of the compiler with no run time representation.</p>
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  29. 

  30. 

  31.         </div><p><small>Last revised: January 26, 2019 at 23:38:56 UTC</small></p>
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