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| author | Anas Nashif <anas.nashif@intel.com> | 2012-10-30 12:57:26 -0700 |
|---|---|---|
| committer | Anas Nashif <anas.nashif@intel.com> | 2012-10-30 12:57:26 -0700 |
| commit | 1a78a62555be32868418fe52f8e330c9d0f95d5a (patch) | |
| tree | d3765a80e7d3b9640ec2e930743630cd6b9fce2b /doc/html/any.html | |
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Imported Upstream version 1.49.0upstream/1.49.0
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diff --git a/doc/html/any.html b/doc/html/any.html new file mode 100644 index 0000000000..2370786fea --- /dev/null +++ b/doc/html/any.html @@ -0,0 +1,112 @@ +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> +<title>Chapter 2. Boost.Any</title> +<link rel="stylesheet" href="../../doc/src/boostbook.css" type="text/css"> +<meta name="generator" content="DocBook XSL Stylesheets V1.76.1"> +<link rel="home" href="index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> +<link rel="up" href="libraries.html" title="Part I. The Boost C++ Libraries (BoostBook Subset)"> +<link rel="prev" href="boost/numeric/functional/as_one_T__std_vector_ta_id581523.html" title="Struct template as_one<T, std_vector_tag>"> +<link rel="next" href="any/s02.html" title="Examples"> +</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="boost/numeric/functional/as_one_T__std_vector_ta_id581523.html"><img src="../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="libraries.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="any/s02.html"><img src="../../doc/src/images/next.png" alt="Next"></a> +</div> +<div class="chapter"> +<div class="titlepage"><div> +<div><h2 class="title"> +<a name="any"></a>Chapter 2. Boost.Any</h2></div> +<div><div class="author"><h3 class="author"> +<span class="firstname">Kevlin</span> <span class="surname">Henney</span> +</h3></div></div> +<div><p class="copyright">Copyright © 2001 Kevlin Henney</p></div> +<div><div class="legalnotice"> +<a name="id1028189"></a><p>Distributed under the Boost Software License, Version 1.0. + (See accompanying file <code class="filename">LICENSE_1_0.txt</code> 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></div> +</div></div> +<div class="toc"> +<p><b>Table of Contents</b></p> +<dl> +<dt><span class="section"><a href="any.html#id1028213">Introduction</a></span></dt> +<dt><span class="section"><a href="any/s02.html">Examples</a></span></dt> +<dt><span class="section"><a href="any/reference.html">Reference</a></span></dt> +<dd><dl> +<dt><span class="section"><a href="any/reference.html#any.ValueType"><span class="emphasis"><em>ValueType</em></span> requirements</a></span></dt> +<dt><span class="section"><a href="any/reference.html#header.boost.any_hpp">Header <boost/any.hpp></a></span></dt> +</dl></dd> +<dt><span class="section"><a href="any/s04.html">Acknowledgements</a></span></dt> +</dl> +</div> +<div class="section"> +<div class="titlepage"><div><div><h2 class="title" style="clear: both"> +<a name="id1028213"></a>Introduction</h2></div></div></div> +<p>There are times when a generic (in the sense of + <span class="emphasis"><em>general</em></span> as opposed to + <span class="emphasis"><em>template-based programming</em></span>) type is needed: + variables that are truly variable, accommodating values of many + other more specific types rather than C++'s normal strict and + static types. We can distinguish three basic kinds of generic + type:</p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"> +<li class="listitem"><p>Converting types that can hold one of a number of + possible value types, e.g. <code class="computeroutput">int</code> and + <code class="computeroutput">string</code>, and freely convert between them, for + instance interpreting <code class="computeroutput">5</code> as <code class="computeroutput">"5"</code> or + vice-versa. Such types are common in scripting and other + interpreted + languages. + <code class="computeroutput">boost::lexical_cast</code> + supports such conversion functionality.</p></li> +<li class="listitem"><p> + Discriminated types that contain values of different types but + do not attempt conversion between them, i.e. <code class="computeroutput">5</code> is + held strictly as an <code class="computeroutput">int</code> and is not implicitly + convertible either to <code class="computeroutput">"5"</code> or to + <code class="computeroutput">5.0</code>. Their indifference to interpretation but + awareness of type effectively makes them safe, generic + containers of single values, with no scope for surprises from + ambiguous conversions.</p></li> +<li class="listitem"><p> + Indiscriminate types that can refer to anything but are + oblivious to the actual underlying type, entrusting all forms + of access and interpretation to the programmer. This niche is + dominated by <code class="computeroutput">void *</code>, which offers plenty of scope + for surprising, undefined behavior.</p></li> +</ul></div> +<p>The <code class="computeroutput"><a class="link" href="boost/any.html" title="Class any">boost::any</a></code> class + (based on the class of the same name described in <a href="http://www.two-sdg.demon.co.uk/curbralan/papers/ValuedConversions.pdf" target="_top">"Valued + Conversions"</a> by Kevlin Henney, <span class="emphasis"><em>C++ + Report</em></span> 12(7), July/August 2000) is a variant value type + based on the second category. It supports copying of any value + type and safe checked extraction of that value strictly against + its type. A similar design, offering more appropriate operators, + can be used for a generalized function adaptor, + <code class="computeroutput">any_function</code>, a generalized iterator adaptor, + <code class="computeroutput">any_iterator</code>, and other object types that need + uniform runtime treatment but support only compile-time template + parameter conformance.</p> +</div> +</div> +<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> +<td align="left"><p><small>Last revised: July 26, 2009 at 21:11:03 +0100</small></p></td> +<td align="right"><div class="copyright-footer"></div></td> +</tr></table> +<hr> +<div class="spirit-nav"> +<a accesskey="p" href="boost/numeric/functional/as_one_T__std_vector_ta_id581523.html"><img src="../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="libraries.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="any/s02.html"><img src="../../doc/src/images/next.png" alt="Next"></a> +</div> +</body> +</html> |