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<title>failure_type&lt;EC, EP = void&gt; - Boost.Outcome documentation</title>
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  <div class="titlepage"><div><div><h1 style="clear: both"><code>failure_type&lt;EC, EP = void&gt;</code></h1></div></div></div>
  <p>Type sugar for constructing an unsuccessful result or outcome. Generally not constructed directly, but via the free function <a href="../../reference/functions/failure.html" class="api-reference"><code>failure(T &amp;&amp;, ...)</code></a>
. Detectable using <a href="../../reference/traits/is_failure_type.html" class="api-reference"><code>is_failure_type&lt;T&gt;</code></a>
.</p>

<p>This is a regular wrapper type, with defaulted default, copy and move constructor, defaulted assignment, and defaulted destructor.</p>

<p>Member type aliases <code>error_type</code> and <code>exception_type</code> indicate <code>EC</code> and <code>E</code>.</p>

<p>There is an explicit initialising constructor taking any types <code>U</code> and <code>V</code> which will forward construct the contained <code>error_type</code> and <code>exception_type</code> respectively.</p>

<p>There are two tagged initialising constructors taking <code>in_place_type_t&lt;error_type&gt;</code> or <code>in_place_type_t&lt;exception_type&gt;</code>, and a <code>U</code> which will forward construct the contained <code>error_type</code> and <code>exception_type</code> respectively.</p>

<p>There are <code>.error()</code> and <code>.exception()</code> reference observers with the usual constexpr lvalue, const lvalue, rvalue and const rvalue overloads. One can discover which or both of these is valid using the usual <code>.has_error()</code> and <code>.has_exception()</code> observers.</p>

<p>There are specialisations <code>failure_type&lt;EC, void&gt;</code> and <code>failure_type&lt;void, E&gt;</code> which store nothing for the voided type and do not provide their observer functions.</p>

<p><em>Requires</em>: Nothing.</p>

<p><em>Namespace</em>: <code>BOOST_OUTCOME_V2_NAMESPACE</code></p>

<p><em>Header</em>: <code>&lt;boost/outcome/success_failure.hpp&gt;</code></p>


        </div><p><small>Last revised: January 24, 2019 at 01:15:16 UTC</small></p>
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