1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>basic_yield_context::operator[]</title> 5<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../boost_asio.html" title="Boost.Asio"> 8<link rel="up" href="../basic_yield_context.html" title="basic_yield_context"> 9<link rel="prev" href="caller_type.html" title="basic_yield_context::caller_type"> 10<link rel="next" href="../bind_executor.html" title="bind_executor"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="caller_type.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../basic_yield_context.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../boost_asio.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../bind_executor.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="boost_asio.reference.basic_yield_context.operator_lb__rb_"></a><a class="link" href="operator_lb__rb_.html" title="basic_yield_context::operator[]">basic_yield_context::operator[]</a> 28</h4></div></div></div> 29<p> 30 <a class="indexterm" name="boost_asio.indexterm.basic_yield_context.operator_lb__rb_"></a> 31Return 32 a yield context that sets the specified error_code. 33 </p> 34<pre class="programlisting">basic_yield_context operator[]( 35 boost::system::error_code & ec) const; 36</pre> 37<p> 38 By default, when a yield context is used with an asynchronous operation, 39 a non-success error_code is converted to system_error and thrown. This 40 operator may be used to specify an error_code object that should instead 41 be set with the asynchronous operation's result. For example: 42 </p> 43<pre class="programlisting">template <typename Handler> 44void my_coroutine(basic_yield_context<Handler> yield) 45{ 46 ... 47 std::size_t n = my_socket.async_read_some(buffer, yield[ec]); 48 if (ec) 49 { 50 // An error occurred. 51 } 52 ... 53} 54</pre> 55</div> 56<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 57<td align="left"></td> 58<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 59 Kohlhoff<p> 60 Distributed under the Boost Software License, Version 1.0. (See accompanying 61 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 62 </p> 63</div></td> 64</tr></table> 65<hr> 66<div class="spirit-nav"> 67<a accesskey="p" href="caller_type.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../basic_yield_context.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../boost_asio.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../bind_executor.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 68</div> 69</body> 70</html> 71
