3
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
4
<title>Reference</title>
5
<link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css">
6
<meta name="generator" content="DocBook XSL Stylesheets V1.76.1">
7
<link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset">
8
<link rel="up" href="../any.html" title="Chapter 2. Boost.Any">
9
<link rel="prev" href="s02.html" title="Examples">
10
<link rel="next" href="../boost/bad_any_cast.html" title="Class bad_any_cast">
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>
22
<div class="spirit-nav">
23
<a accesskey="p" href="s02.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../any.html"><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="../boost/bad_any_cast.html"><img src="../../../doc/src/images/next.png" alt="Next"></a>
26
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
27
<a name="any.reference"></a>Reference</h2></div></div></div>
29
<dt><span class="section"><a href="reference.html#any.ValueType"><span class="emphasis"><em>ValueType</em></span> requirements</a></span></dt>
30
<dt><span class="section"><a href="reference.html#header.boost.any_hpp">Header <boost/any.hpp></a></span></dt>
33
<div class="titlepage"><div><div><h3 class="title">
34
<a name="any.ValueType"></a><span class="emphasis"><em>ValueType</em></span> requirements</h3></div></div></div>
35
<p>Values are strongly informational objects for which
36
identity is not significant, i.e. the focus is principally on
37
their state content and any behavior organized around
38
that. Another distinguishing feature of values is their
39
granularity: normally fine-grained objects representing simple
40
concepts in the system such as quantities.</p>
41
<p>As the emphasis of a value lies in its state not its
42
identity, values can be copied and typically assigned one to
43
another, requiring the explicit or implicit definition of a
44
public copy constructor and public assignment operator. Values
45
typically live within other scopes, i.e. within objects or
46
blocks, rather than on the heap. Values are therefore normally
47
passed around and manipulated directly as variables or through
48
references, but not as pointers that emphasize identity and
50
<p>The specific requirements on value types to be used in an
51
<code class="computeroutput"><a class="link" href="../boost/any.html" title="Class any">any</a></code>
53
<div class="itemizedlist"><ul class="itemizedlist" type="disc" compact>
54
<li class="listitem">A <span class="emphasis"><em>ValueType</em></span> is
55
<span class="emphasis"><em>CopyConstructible</em></span> [20.1.3].</li>
56
<li class="listitem">A <span class="emphasis"><em>ValueType</em></span> is
57
optionally <span class="emphasis"><em>Assignable</em></span> [23.1]. The strong
58
exception-safety guarantee is required for all forms of
60
<li class="listitem">The destructor for a
61
<span class="emphasis"><em>ValueType</em></span> upholds the no-throw
62
exception-safety guarantee.</li>
66
<div class="titlepage"><div><div><h3 class="title">
67
<a name="header.boost.any_hpp"></a>Header <<a href="../../../boost/any.hpp" target="_top">boost/any.hpp</a>></h3></div></div></div>
68
<pre class="synopsis"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span>
69
<span class="keyword">class</span> <a class="link" href="../boost/bad_any_cast.html" title="Class bad_any_cast">bad_any_cast</a><span class="special">;</span>
70
<span class="keyword">class</span> <a class="link" href="../boost/any.html" title="Class any">any</a><span class="special">;</span>
71
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> <span class="identifier">T</span> <a class="link" href="../boost/any_cast.html" title="Function any_cast"><span class="identifier">any_cast</span></a><span class="special">(</span><a class="link" href="../boost/any.html" title="Class any">any</a> <span class="special">&</span><span class="special">)</span><span class="special">;</span>
72
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> <span class="identifier">T</span> <a class="link" href="../boost/any_cast.html" title="Function any_cast"><span class="identifier">any_cast</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="../boost/any.html" title="Class any">any</a> <span class="special">&</span><span class="special">)</span><span class="special">;</span>
73
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> ValueType<span class="special">></span> <span class="keyword">const</span> <span class="identifier">ValueType</span> <span class="special">*</span> <a class="link" href="../boost/any_cast.html" title="Function any_cast"><span class="identifier">any_cast</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="../boost/any.html" title="Class any">any</a> <span class="special">*</span><span class="special">)</span><span class="special">;</span>
74
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> ValueType<span class="special">></span> <span class="identifier">ValueType</span> <span class="special">*</span> <a class="link" href="../boost/any_cast.html" title="Function any_cast"><span class="identifier">any_cast</span></a><span class="special">(</span><a class="link" href="../boost/any.html" title="Class any">any</a> <span class="special">*</span><span class="special">)</span><span class="special">;</span>
75
<span class="special">}</span></pre>
78
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
79
<td align="left"></td>
80
<td align="right"><div class="copyright-footer">Copyright © 2001 Kevlin Henney<p>Distributed under the Boost Software License, Version 1.0.
81
(See accompanying file <code class="filename">LICENSE_1_0.txt</code> or copy at
82
<a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
87
<div class="spirit-nav">
88
<a accesskey="p" href="s02.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../any.html"><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="../boost/bad_any_cast.html"><img src="../../../doc/src/images/next.png" alt="Next"></a>