1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html><meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 3<title>BOOST_OUTCOME_TRYX_FAILURE_LIKELY(expr) - Boost.Outcome documentation</title> 4<link rel="stylesheet" href="../../css/boost.css" type="text/css"> 5<meta name="generator" content="Hugo 0.52 with Boostdoc theme"> 6<meta name="viewport" content="width=device-width,initial-scale=1.0"/> 7 8<link rel="icon" href="../../images/favicon.ico" type="image/ico"/> 9<body><div class="spirit-nav"> 10<a accesskey="p" href="../../reference/macros/tryx.html"><img src="../../images/prev.png" alt="Prev"></a> 11 <a accesskey="u" href="../../reference/macros.html"><img src="../../images/up.png" alt="Up"></a> 12 <a accesskey="h" href="../../index.html"><img src="../../images/home.png" alt="Home"></a><a accesskey="n" href="../../reference/macros/try_failure_likely.html"><img src="../../images/next.png" alt="Next"></a></div><div id="content"> 13 <div class="titlepage"><div><div><h1 style="clear: both"><code>BOOST_OUTCOME_TRYX_FAILURE_LIKELY(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 unsuccessful. If you expect success, you should use <a href="../../reference/macros/tryx.html" class="api-reference"><code>BOOST_OUTCOME_TRYX(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>’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><boost/outcome/try.hpp></code></p> 44 45 46 </div><p><small>Last revised: October 16, 2019 at 10:26:35 +0100</small></p> 47<hr> 48<div class="spirit-nav"> 49<a accesskey="p" href="../../reference/macros/tryx.html"><img src="../../images/prev.png" alt="Prev"></a> 50 <a accesskey="u" href="../../reference/macros.html"><img src="../../images/up.png" alt="Up"></a> 51 <a accesskey="h" href="../../index.html"><img src="../../images/home.png" alt="Home"></a><a accesskey="n" href="../../reference/macros/try_failure_likely.html"><img src="../../images/next.png" alt="Next"></a></div></body> 52</html> 53
