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  13   <div class="titlepage"><div><div><h1 style="clear: both"><code>BOOST_OUTCOME_TRYX(expr)</code></h1></div></div></div>
  14   <p>Evaluate an expression which results in a type matching the following customisation points, emitting the <code>T</code> if successful, immediately returning <a href="../../reference/functions/try_operation_return_as.html" class="api-reference"><code>try_operation_return_as(X)</code></a>
  15  from the calling function if unsuccessful:</p>
  16
  17 <ul>
  18 <li><code>BOOST_OUTCOME_V2_NAMESPACE::</code><a href="../../reference/functions/try_operation_has_value.html" class="api-reference"><code>try_operation_has_value(X)</code></a>
  19 </li>
  20 <li><code>BOOST_OUTCOME_V2_NAMESPACE::</code><a href="../../reference/functions/try_operation_return_as.html" class="api-reference"><code>try_operation_return_as(X)</code></a>
  21 </li>
  22 <li><code>BOOST_OUTCOME_V2_NAMESPACE::</code><a href="../../reference/functions/try_operation_extract_value.html" class="api-reference"><code>try_operation_extract_value(X)</code></a>
  23 </li>
  24 </ul>
  25
  26 <p>Default overloads for these customisation points are provided. See <a href="../../recipes/foreign-try.html">the recipe for supporting foreign input to <code>BOOST_OUTCOME_TRY</code></a>.</p>
  27
  28 <p>Hints are given to the compiler that the expression will be successful. If you expect failure, you should use <a href="../../reference/macros/tryx_failure_likely.html" class="api-reference"><code>BOOST_OUTCOME_TRYX_FAILURE_LIKELY(expr)</code></a>
  29  instead.</p>
  30
  31 <p><em>Availability</em>: GCC and clang only. Use <code>#ifdef BOOST_OUTCOME_TRYX</code> to determine if available.</p>
  32
  33 <p><em>Overridable</em>: Not overridable.</p>
  34
  35 <p><em>Definition</em>: See <a href="../../reference/macros/tryv.html" class="api-reference"><code>BOOST_OUTCOME_TRYV(expr)</code></a>
  36  for most of the mechanics.</p>
  37
  38 <p>This macro makes use of a proprietary extension in GCC and clang to emit the <code>T</code> from a successful expression. You can thus use <code>BOOST_OUTCOME_TRYX(expr)</code> directly in expressions e.g. <code>auto x = y + BOOST_OUTCOME_TRYX(foo(z));</code>.</p>
  39
  40 <p>Be aware there are compiler quirks in preserving the rvalue/lvalue/etc-ness of emitted <code>T</code>&rsquo;s, specifically copy or move constructors may be called unexpectedly and/or copy elision not work as expected. If these prove to be problematic, use <a href="../../reference/macros/try.html" class="api-reference"><code>BOOST_OUTCOME_TRY(var, expr)</code></a>
  41  instead.</p>
  42
  43 <p><em>Header</em>: <code>&lt;boost/outcome/try.hpp&gt;</code></p>
  44
  45
  46         </div><p><small>Last revised: October 16, 2019 at 10:26:35 &#43;0100</small></p>
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