1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>execution::connect</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="../reference.html" title="Reference"> 9<link rel="prev" href="execution__can_submit.html" title="execution::can_submit"> 10<link rel="next" href="execution__connect_result.html" title="execution::connect_result"> 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="execution__can_submit.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.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="execution__connect_result.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h3 class="title"> 27<a name="boost_asio.reference.execution__connect"></a><a class="link" href="execution__connect.html" title="execution::connect">execution::connect</a> 28</h3></div></div></div> 29<p> 30 <a class="indexterm" name="boost_asio.indexterm.execution__connect"></a> 31A customisation 32 point that connects a sender to a receiver. 33 </p> 34<pre class="programlisting">constexpr unspecified connect = unspecified; 35</pre> 36<p> 37 The name <code class="computeroutput">execution::connect</code> denotes a customisation point object. 38 For some subexpressions <code class="computeroutput">s</code> and <code class="computeroutput">r</code>, let <code class="computeroutput">S</code> 39 be a type such that <code class="computeroutput">decltype((s))</code> is <code class="computeroutput">S</code> and let 40 <code class="computeroutput">R</code> be a type such that <code class="computeroutput">decltype((r))</code> is <code class="computeroutput">R</code>. 41 The expression <code class="computeroutput">execution::connect(s, r)</code> is expression-equivalent 42 to: 43 </p> 44<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 45<li class="listitem"> 46 <code class="computeroutput">s.connect(r)</code>, if that expression is valid, if its type satisfies 47 <code class="computeroutput">operation_state</code>, and if <code class="computeroutput">S</code> satisfies <code class="computeroutput">sender</code>. 48 </li> 49<li class="listitem"> 50 Otherwise, <code class="computeroutput">connect(s, r)</code>, if that expression is valid, if 51 its type satisfies <code class="computeroutput">operation_state</code>, and if <code class="computeroutput">S</code> 52 satisfies <code class="computeroutput">sender</code>, with overload resolution performed in 53 a context that includes the declaration <code class="computeroutput">void connect();</code> 54 and that does not include a declaration of <code class="computeroutput">execution::connect</code>. 55 </li> 56<li class="listitem"> 57 Otherwise, <code class="computeroutput">as_operation{s, r}</code>, if <code class="computeroutput">r</code> is not 58 an instance of <code class="computeroutput">as_receiver<F, S></code> for some type <code class="computeroutput">F</code>, 59 and if <code class="computeroutput">receiver_of<R> && executor_of<remove_cvref_t<S>, 60 as_invocable<remove_cvref_t<R>, S>></code> is <code class="computeroutput">true</code>, 61 where <code class="computeroutput">as_operation</code> is an implementation-defined class equivalent 62 to 63 </li> 64</ul></div> 65<pre class="programlisting">template <class S, class R> 66 struct as_operation 67 { 68 remove_cvref_t<S> e_; 69 remove_cvref_t<R> r_; 70 void start() noexcept try { 71 execution::execute(std::move(e_), 72 as_invocable<remove_cvref_t<R>, S>{r_}); 73 } catch(...) { 74 execution::set_error(std::move(r_), current_exception()); 75 } 76 }; 77</pre> 78<p> 79 and <code class="computeroutput">as_invocable</code> is a class template equivalent to the following: 80 </p> 81<pre class="programlisting">template<class R> 82 struct as_invocable 83 { 84 R* r_; 85 explicit as_invocable(R& r) noexcept 86 : r_(std::addressof(r)) {} 87 as_invocable(as_invocable && other) noexcept 88 : r_(std::exchange(other.r_, nullptr)) {} 89 ~as_invocable() { 90 if(r_) 91 execution::set_done(std::move(*r_)); 92 } 93 void operator()() & noexcept try { 94 execution::set_value(std::move(*r_)); 95 r_ = nullptr; 96 } catch(...) { 97 execution::set_error(std::move(*r_), current_exception()); 98 r_ = nullptr; 99 } 100 }; 101</pre> 102<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> 103 Otherwise, <code class="computeroutput">execution::connect(s, r)</code> is ill-formed. 104 </li></ul></div> 105<h5> 106<a name="boost_asio.reference.execution__connect.h0"></a> 107 <span class="phrase"><a name="boost_asio.reference.execution__connect.requirements"></a></span><a class="link" href="execution__connect.html#boost_asio.reference.execution__connect.requirements">Requirements</a> 108 </h5> 109<p> 110 <span class="emphasis"><em>Header: </em></span><code class="literal">boost/asio/execution/connect.hpp</code> 111 </p> 112<p> 113 <span class="emphasis"><em>Convenience header: </em></span><code class="literal">boost/asio/execution.hpp</code> 114 </p> 115</div> 116<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 117<td align="left"></td> 118<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 119 Kohlhoff<p> 120 Distributed under the Boost Software License, Version 1.0. (See accompanying 121 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>) 122 </p> 123</div></td> 124</tr></table> 125<hr> 126<div class="spirit-nav"> 127<a accesskey="p" href="execution__can_submit.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.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="execution__connect_result.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 128</div> 129</body> 130</html> 131
