<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Time traits requirements</title>
<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
<link rel="home" href="../../boost_asio.html" title="Boost.Asio">
<link rel="up" href="../reference.html" title="Reference">
<link rel="prev" href="SyncWriteStream.html" title="Buffer-oriented synchronous write stream requirements">
<link rel="next" href="TimerService.html" title="Timer service requirements">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td>
<td align="center"><a href="../../../../index.html">Home</a></td>
<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="SyncWriteStream.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="TimerService.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_asio.reference.TimeTraits"></a><a class="link" href="TimeTraits.html" title="Time traits requirements">Time traits requirements</a>
</h3></div></div></div>
<p>
In the table below, <code class="computeroutput"><span class="identifier">X</span></code> denotes
a time traits class for time type <code class="computeroutput"><span class="identifier">Time</span></code>,
<code class="computeroutput"><span class="identifier">t</span></code>, <code class="computeroutput"><span class="identifier">t1</span></code>,
and <code class="computeroutput"><span class="identifier">t2</span></code> denote values of type
<code class="computeroutput"><span class="identifier">Time</span></code>, and <code class="computeroutput"><span class="identifier">d</span></code>
denotes a value of type <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">duration_type</span></code>.
</p>
<div class="table">
<a name="boost_asio.reference.TimeTraits.t0"></a><p class="title"><b>Table 38. TimeTraits requirements</b></p>
<div class="table-contents"><table class="table" summary="TimeTraits requirements">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
expression
</p>
</th>
<th>
<p>
return type
</p>
</th>
<th>
<p>
assertion/note<br> pre/post-condition
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">time_type</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">Time</span></code>
</p>
</td>
<td>
<p>
Represents an absolute time. Must support default construction,
and meet the requirements for <code class="computeroutput"><span class="identifier">CopyConstructible</span></code>
and <code class="computeroutput"><span class="identifier">Assignable</span></code>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">duration_type</span></code>
</p>
</td>
<td>
</td>
<td>
<p>
Represents the difference between two absolute times. Must support
default construction, and meet the requirements for <code class="computeroutput"><span class="identifier">CopyConstructible</span></code> and <code class="computeroutput"><span class="identifier">Assignable</span></code>. A duration can be
positive, negative, or zero.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">time_type</span></code>
</p>
</td>
<td>
<p>
Returns the current time.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">add</span><span class="special">(</span><span class="identifier">t</span><span class="special">,</span>
<span class="identifier">d</span><span class="special">);</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">time_type</span></code>
</p>
</td>
<td>
<p>
Returns a new absolute time resulting from adding the duration
<code class="computeroutput"><span class="identifier">d</span></code> to the absolute
time <code class="computeroutput"><span class="identifier">t</span></code>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">subtract</span><span class="special">(</span><span class="identifier">t1</span><span class="special">,</span>
<span class="identifier">t2</span><span class="special">);</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">duration_type</span></code>
</p>
</td>
<td>
<p>
Returns the duration resulting from subtracting <code class="computeroutput"><span class="identifier">t2</span></code>
from <code class="computeroutput"><span class="identifier">t1</span></code>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">less_than</span><span class="special">(</span><span class="identifier">t1</span><span class="special">,</span>
<span class="identifier">t2</span><span class="special">);</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">bool</span></code>
</p>
</td>
<td>
<p>
Returns whether <code class="computeroutput"><span class="identifier">t1</span></code>
is to be treated as less than <code class="computeroutput"><span class="identifier">t2</span></code>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">to_posix_duration</span><span class="special">(</span><span class="identifier">d</span><span class="special">);</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">date_time</span><span class="special">::</span><span class="identifier">time_duration_type</span></code>
</p>
</td>
<td>
<p>
Returns the <code class="computeroutput"><span class="identifier">date_time</span><span class="special">::</span><span class="identifier">time_duration_type</span></code>
value that most closely represents the duration <code class="computeroutput"><span class="identifier">d</span></code>.
</p>
</td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break">
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2003-2015 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>)
</p>
</div></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="SyncWriteStream.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="TimerService.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
