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<h1 class="heading-title">
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<a href="../../">
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<img src="../../images/space.png" alt="Boost C++ Libraries" class="heading-logo" />
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<span class="heading-boost">Boost</span>
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<q>...one of the most highly
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">The Application</h2></div></div></div>
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<p>The application is of course also based on Outcome, and like the HTTP library
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is also of mixed-failure design in that failure can be returned via error code,
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type erased <code>exception_ptr</code> or indeed a C++ exception throw.</p>
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<div class="code-snippet"><div class="highlight"><pre class="chroma"><code class="language-c++" data-lang="c++"><span class="c1">// This is the namespace of the application which is connecting together the httplib,
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</span><span class="c1">// filelib and tidylib libraries into a solution.
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</span><span class="c1"></span><span class="k">namespace</span> <span class="n">app</span>
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<span class="p">{</span>
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<span class="c1">// Create an ADL bridge so copy/move hooks will be searched for in this namespace
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</span><span class="c1"></span> <span class="k">struct</span> <span class="nl">error_code</span> <span class="p">:</span> <span class="k">public</span> <span class="n">std</span><span class="o">::</span><span class="n">error_code</span>
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<span class="p">{</span>
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<span class="c1">// passthrough
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</span><span class="c1"></span> <span class="k">using</span> <span class="n">std</span><span class="o">::</span><span class="n">error_code</span><span class="o">::</span><span class="n">error_code</span><span class="p">;</span>
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<span class="n">error_code</span><span class="p">()</span> <span class="o">=</span> <span class="k">default</span><span class="p">;</span>
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<span class="n">error_code</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">error_code</span> <span class="n">ec</span><span class="p">)</span>
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<span class="o">:</span> <span class="n">std</span><span class="o">::</span><span class="n">error_code</span><span class="p">(</span><span class="n">ec</span><span class="p">)</span>
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<span class="p">{</span>
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<span class="p">}</span>
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<span class="p">};</span>
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<span class="c1">// Localise an outcome implementation for this namespace
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</span><span class="c1"></span> <span class="k">template</span> <span class="o"><</span><span class="k">class</span><span class="err"> </span><span class="nc">T</span><span class="o">></span> <span class="k">using</span> <span class="n">outcome</span> <span class="o">=</span> <span class="n">BOOST_OUTCOME_V2_NAMESPACE</span><span class="o">::</span><span class="n">outcome</span><span class="o"><</span><span class="n">T</span><span class="p">,</span> <span class="n">error_code</span> <span class="cm">/*, std::exception_ptr */</span><span class="o">></span><span class="p">;</span>
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<span class="k">using</span> <span class="n">BOOST_OUTCOME_V2_NAMESPACE</span><span class="o">::</span><span class="n">success</span><span class="p">;</span>
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<span class="p">}</span>
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</code></pre></div><a href="https://github.com/ned14/boost-outcome/tree/master/doc/src/snippets/finale.cpp#L162" class="code-snippet-url" target="_blank">View this code on Github</a></div>
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<p>Here we localise a passthrough <code>error_code</code> solely for the purpose of ADL bridging, otherwise
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the localised <code>outcome</code> configured is the default one which comes with Outcome.</p>
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<p>The way we are going to configure interop is as follows:</p>
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<ol>
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<li>The application shall use <code>error_code</code> for anticipated failure and C++
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exception throws for unanticipated failure.</li>
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<li>We shall choose the convention that <code>app::outcome</code> with exception ptr
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solely and exclusively represents a type erased failure from a third party
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library.</li>
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</ol>
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<p>Thus if one calls <code>.value()</code> on an <code>app::outcome</code>, both anticipated failure
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within the app and type erased failure from a third party library shall be
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converted to a C++ exception throw.</p>
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</div><p><small>Last revised: December 05, 2018 at 14:18:52 UTC</small></p>
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