1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Function null_old</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="../../index.html" title="Chapter 1. Boost.Contract 1.0.0"> 8<link rel="up" href="../../reference.html#header.boost.contract.old_hpp" title="Header <boost/contract/old.hpp>"> 9<link rel="prev" href="old_value_copy.html" title="Struct template old_value_copy"> 10<link rel="next" href="make_old_idm46268584781184.html" title="Function make_old"> 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="old_value_copy.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../reference.html#header.boost.contract.old_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="make_old_idm46268584781184.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="refentry"> 26<a name="boost.contract.null_old"></a><div class="titlepage"></div> 27<div class="refnamediv"> 28<h2><span class="refentrytitle">Function null_old</span></h2> 29<p>boost::contract::null_old — Return a "null" old value. </p> 30</div> 31<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 32<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="../../reference.html#header.boost.contract.old_hpp" title="Header <boost/contract/old.hpp>">boost/contract/old.hpp</a>> 33 34</span> 35<a class="link" href="old_value.html" title="Class old_value">old_value</a> <span class="identifier">null_old</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></pre></div> 36<div class="refsect1"> 37<a name="idm45988677013472"></a><h2>Description</h2> 38<p>The related old value pointer will also be null. This function is usually only called by the code expanded by <code class="computeroutput"><code class="computeroutput"><a class="link" href="../../BOOST_CONTRACT_OLDOF.html" title="Macro BOOST_CONTRACT_OLDOF">BOOST_CONTRACT_OLDOF</a></code></code>.</p> 39<p><span class="bold"><strong>See Also:</strong></span></p> 40<p> <a class="link" href="../../boost_contract/extras.html#boost_contract.extras.no_macros__and_no_variadic_macros_" title="No Macros (and No Variadic Macros)"> No Macros</a></p> 41<p> 42</p> 43<p> 44 45</p> 46<div class="variablelist"><table border="0" class="variablelist compact"> 47<colgroup> 48<col align="left" valign="top"> 49<col> 50</colgroup> 51<tbody><tr> 52<td><p><span class="term">Returns:</span></p></td> 53<td><p>Null old value. </p></td> 54</tr></tbody> 55</table></div> 56</div> 57</div> 58<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 59<td align="left"></td> 60<td align="right"><div class="copyright-footer">Copyright © 2008-2019 Lorenzo Caminiti<p> 61 Distributed under the Boost Software License, Version 1.0 (see accompanying 62 file LICENSE_1_0.txt or a copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 63 </p> 64</div></td> 65</tr></table> 66<hr> 67<div class="spirit-nav"> 68<a accesskey="p" href="old_value_copy.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../reference.html#header.boost.contract.old_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="make_old_idm46268584781184.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 69</div> 70</body> 71</html> 72
