execution__connect.html
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<div class="titlepage"><div><div><h3 class="title">
<a name="asio.reference.execution__connect"></a><a class="link" href="execution__connect.html" title="execution::connect">execution::connect</a>
</h3></div></div></div>
<p>
<a class="indexterm" name="asio.indexterm.execution__connect"></a>
A customisation point
that connects a sender to a receiver.
</p>
<pre class="programlisting">constexpr unspecified connect = unspecified;
</pre>
<p>
The name <code class="computeroutput">execution::connect</code> denotes a customisation point object.
For some subexpressions <code class="computeroutput">s</code> and <code class="computeroutput">r</code>, let <code class="computeroutput">S</code>
be a type such that <code class="computeroutput">decltype((s))</code> is <code class="computeroutput">S</code> and let
<code class="computeroutput">R</code> be a type such that <code class="computeroutput">decltype((r))</code> is <code class="computeroutput">R</code>.
The expression <code class="computeroutput">execution::connect(s, r)</code> is expression-equivalent
to:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
<code class="computeroutput">s.connect(r)</code>, if that expression is valid, if its type satisfies
<code class="computeroutput">operation_state</code>, and if <code class="computeroutput">S</code> satisfies <code class="computeroutput">sender</code>.
</li>
<li class="listitem">
Otherwise, <code class="computeroutput">connect(s, r)</code>, if that expression is valid, if
its type satisfies <code class="computeroutput">operation_state</code>, and if <code class="computeroutput">S</code>
satisfies <code class="computeroutput">sender</code>, with overload resolution performed in
a context that includes the declaration <code class="computeroutput">void connect();</code>
and that does not include a declaration of <code class="computeroutput">execution::connect</code>.
</li>
<li class="listitem">
Otherwise, <code class="computeroutput">as_operation{s, r}</code>, if <code class="computeroutput">r</code> is not
an instance of <code class="computeroutput">as_receiver<F, S></code> for some type <code class="computeroutput">F</code>,
and if <code class="computeroutput">receiver_of<R> && executor_of<remove_cvref_t<S>,
as_invocable<remove_cvref_t<R>, S>></code> is <code class="computeroutput">true</code>,
where <code class="computeroutput">as_operation</code> is an implementation-defined class equivalent
to
</li>
</ul></div>
<pre class="programlisting">template <class S, class R>
struct as_operation
{
remove_cvref_t<S> e_;
remove_cvref_t<R> r_;
void start() noexcept try {
execution::execute(std::move(e_),
as_invocable<remove_cvref_t<R>, S>{r_});
} catch(...) {
execution::set_error(std::move(r_), current_exception());
}
};
</pre>
<p>
and <code class="computeroutput">as_invocable</code> is a class template equivalent to the following:
</p>
<pre class="programlisting">template<class R>
struct as_invocable
{
R* r_;
explicit as_invocable(R& r) noexcept
: r_(std::addressof(r)) {}
as_invocable(as_invocable && other) noexcept
: r_(std::exchange(other.r_, nullptr)) {}
~as_invocable() {
if(r_)
execution::set_done(std::move(*r_));
}
void operator()() & noexcept try {
execution::set_value(std::move(*r_));
r_ = nullptr;
} catch(...) {
execution::set_error(std::move(*r_), current_exception());
r_ = nullptr;
}
};
</pre>
<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Otherwise, <code class="computeroutput">execution::connect(s, r)</code> is ill-formed.
</li></ul></div>
<h5>
<a name="asio.reference.execution__connect.h0"></a>
<span><a name="asio.reference.execution__connect.requirements"></a></span><a class="link" href="execution__connect.html#asio.reference.execution__connect.requirements">Requirements</a>
</h5>
<p>
<span class="emphasis"><em>Header: </em></span><code class="literal">asio/execution/connect.hpp</code>
</p>
<p>
<span class="emphasis"><em>Convenience header: </em></span><code class="literal">asio/execution.hpp</code>
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M.
Kohlhoff<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
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>)
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