1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5<title>Function template value</title> 6<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="../../yap/reference.html#header.boost.yap.algorithm_hpp" title="Header <boost/yap/algorithm.hpp>"> 10<link rel="prev" href="deref.html" title="Function template deref"> 11<link rel="next" href="get.html" title="Function template get"> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td> 16<td align="center"><a href="../../../../index.html">Home</a></td> 17<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td> 18<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 19<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 20<td align="center"><a href="../../../../more/index.htm">More</a></td> 21</tr></table> 22<hr> 23<div class="spirit-nav"> 24<a accesskey="p" href="deref.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../yap/reference.html#header.boost.yap.algorithm_hpp"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="get.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="refentry"> 27<a name="boost.yap.value"></a><div class="titlepage"></div> 28<div class="refnamediv"> 29<h2><span class="refentrytitle">Function template value</span></h2> 30<p>boost::yap::value</p> 31</div> 32<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 33<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../../yap/reference.html#header.boost.yap.algorithm_hpp" title="Header <boost/yap/algorithm.hpp>">boost/yap/algorithm.hpp</a>> 34 35</span> 36<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> <span class="keyword">decltype</span><span class="special">(</span><span class="keyword">auto</span><span class="special">)</span> <span class="keyword">constexpr</span> <span class="identifier">value</span><span class="special">(</span><span class="identifier">T</span> <span class="special">&&</span> x<span class="special">)</span><span class="special">;</span></pre></div> 37<div class="refsect1"> 38<a name="id-1.3.48.8.2.2.5.4"></a><h2>Description</h2> 39<p>Forwards the sole element of <span class="emphasis"><em>x</em></span> to the caller, possibly calling <code class="computeroutput">deref()</code> first if <span class="emphasis"><em>x</em></span> is a reference expression, or forwards <span class="emphasis"><em>x</em></span> to the caller unchanged.</p> 40<p>More formally:</p> 41<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 42<li class="listitem"><p>If <span class="emphasis"><em>x</em></span> is not an expression, <span class="emphasis"><em>x</em></span> is forwarded to the caller.</p></li> 43<li class="listitem"><p>Otherwise, if <span class="emphasis"><em>x</em></span> is a reference expression, the result is <code class="computeroutput">value(deref(x))</code>.</p></li> 44<li class="listitem"><p>Otherwise, if <span class="emphasis"><em>x</em></span> is an expression with only one value (a unary expression or a terminal expression), the result is the forwarded first element of <span class="emphasis"><em>x</em></span>.</p></li> 45<li class="listitem"><p>Otherwise, <span class="emphasis"><em>x</em></span> is forwarded to the caller. </p></li> 46</ul></div> 47<p> 48</p> 49</div> 50</div> 51<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 52<td align="left"></td> 53<td align="right"><div class="copyright-footer">Copyright © 2018 T. Zachary Laine<p> 54 Distributed under the Boost Software License, Version 1.0. (See accompanying 55 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>) 56 </p> 57</div></td> 58</tr></table> 59<hr> 60<div class="spirit-nav"> 61<a accesskey="p" href="deref.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../yap/reference.html#header.boost.yap.algorithm_hpp"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="get.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 62</div> 63</body> 64</html> 65
