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<title>boost/python/type_id.hpp</title>
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="utility_and_infrastructure.boost_python_type_id_hpp"></a><a class="link" href="boost_python_type_id_hpp.html" title="boost/python/type_id.hpp">boost/python/type_id.hpp</a>
</h2></div></div></div>
<div class="toc"><dl>
<dt><span class="section"><a href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.introduction">Introduction</a></span></dt>
<dt><span class="section"><a href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.class_template_type_info">Class
template <code class="computeroutput"><span class="identifier">type_info</span></code></a></span></dt>
<dt><span class="section"><a href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.functions">Functions</a></span></dt>
<dt><span class="section"><a href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.example">Example</a></span></dt>
</dl></div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="utility_and_infrastructure.boost_python_type_id_hpp.introduction"></a><a class="link" href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.introduction" title="Introduction">Introduction</a>
</h3></div></div></div>
<p>
<boost/python/type_id.hpp> provides types and functions for runtime
type identification like those of of <code class="computeroutput"><span class="special"><</span><span class="identifier">typeinfo</span><span class="special">></span></code>.
It exists mostly to work around certain compiler bugs and platform-dependent
interactions with shared libraries.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="utility_and_infrastructure.boost_python_type_id_hpp.class_template_type_info"></a><a class="link" href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.class_template_type_info" title="Class template type_info">Class
template <code class="computeroutput"><span class="identifier">type_info</span></code></a>
</h3></div></div></div>
<div class="toc"><dl>
<dt><span class="section"><a href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.class_template_type_info.class_template_type_info_constru">Class
template <code class="computeroutput"><span class="identifier">type_info</span></code> constructor</a></span></dt>
<dt><span class="section"><a href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.class_template_type_info.class_template_type_info_compari">Class
template <code class="computeroutput"><span class="identifier">type_info</span></code> comparison</a></span></dt>
<dt><span class="section"><a href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.class_template_type_info.class_template_type_info_observe">Class
template <code class="computeroutput"><span class="identifier">type_info</span></code> observers</a></span></dt>
</dl></div>
<p>
<code class="computeroutput"><span class="identifier">type_info</span></code> instances identify
a type. As <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">type_info</span></code> is specified to (but unlike
its implementation in some compilers), <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">python</span><span class="special">::</span><span class="identifier">type_info</span></code>
never represents top-level references or cv-qualification (see section
5.2.8 in the C++ standard). Unlike <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">type_info</span></code>,
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">python</span><span class="special">::</span><span class="identifier">type_info</span></code> instances are copyable, and
comparisons always work reliably across shared library boundaries.
</p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">python</span>
<span class="special">{</span>
<span class="keyword">class</span> <span class="identifier">type_info</span> <span class="special">:</span> <span class="identifier">totally_ordered</span><span class="special"><</span><span class="identifier">type_info</span><span class="special">></span>
<span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
<span class="comment">// constructor</span>
<span class="identifier">type_info</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">type_info</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">=</span> <span class="keyword">typeid</span><span class="special">(</span><span class="keyword">void</span><span class="special">));</span>
<span class="comment">// comparisons</span>
<span class="keyword">bool</span> <span class="keyword">operator</span><span class="special"><(</span><span class="identifier">type_info</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
<span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==(</span><span class="identifier">type_info</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
<span class="comment">// observers</span>
<span class="keyword">char</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">name</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span>
<span class="special">};</span>
<span class="special">}}</span>
</pre>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="utility_and_infrastructure.boost_python_type_id_hpp.class_template_type_info.class_template_type_info_constru"></a><a class="link" href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.class_template_type_info.class_template_type_info_constru" title="Class template type_info constructor">Class
template <code class="computeroutput"><span class="identifier">type_info</span></code> constructor</a>
</h4></div></div></div>
<pre class="programlisting"><span class="identifier">type_info</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">type_info</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">=</span> <span class="keyword">typeid</span><span class="special">(</span><span class="keyword">void</span><span class="special">));</span></pre>
<div class="variablelist">
<p class="title"><b></b></p>
<dl>
<dt><span class="term">Effects</span></dt>
<dd><p>
constructs a <code class="computeroutput"><span class="identifier">type_info</span></code>
object which identifies the same type as its argument.
</p></dd>
<dt><span class="term">Rationale</span></dt>
<dd><p>
Since it is occasionally necessary to make an array of <code class="computeroutput"><span class="identifier">type_info</span></code> objects a benign default
argument is supplied. Note: this constructor does not correct for
non-conformance of compiler <code class="computeroutput"><span class="keyword">typeid</span><span class="special">()</span></code> implementations. See <code class="computeroutput"><span class="identifier">type_id</span></code>, below.
</p></dd>
</dl>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="utility_and_infrastructure.boost_python_type_id_hpp.class_template_type_info.class_template_type_info_compari"></a><a class="link" href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.class_template_type_info.class_template_type_info_compari" title="Class template type_info comparison">Class
template <code class="computeroutput"><span class="identifier">type_info</span></code> comparison</a>
</h4></div></div></div>
<pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special"><(</span><span class="identifier">type_info</span> <span class="keyword">const</span> <span class="special">&</span><span class="identifier">rhs</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
<div class="variablelist">
<p class="title"><b></b></p>
<dl>
<dt><span class="term">Effects</span></dt>
<dd><p>
yields a total order over <code class="computeroutput"><span class="identifier">type_info</span></code>
objects.
</p></dd>
</dl>
</div>
<pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==(</span><span class="identifier">type_info</span> <span class="keyword">const</span> <span class="special">&</span><span class="identifier">rhs</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
<div class="variablelist">
<p class="title"><b></b></p>
<dl>
<dt><span class="term">Returns</span></dt>
<dd><p>
<code class="computeroutput"><span class="keyword">true</span></code> iff the two values
describe the same type.
</p></dd>
<dt><span class="term">Note</span></dt>
<dd><p>
The use of <code class="computeroutput"><span class="identifier">totally_ordered</span><span class="special"><</span><span class="identifier">type_info</span><span class="special">></span></code> as a private base class supplies
operators <code class="computeroutput"><span class="special"><=</span></code>,
<code class="computeroutput"><span class="special">>=</span></code>, <code class="computeroutput"><span class="special">></span></code>, and <code class="computeroutput"><span class="special">!=</span></code>
</p></dd>
</dl>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="utility_and_infrastructure.boost_python_type_id_hpp.class_template_type_info.class_template_type_info_observe"></a><a class="link" href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.class_template_type_info.class_template_type_info_observe" title="Class template type_info observers">Class
template <code class="computeroutput"><span class="identifier">type_info</span></code> observers</a>
</h4></div></div></div>
<pre class="programlisting"><span class="keyword">char</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">name</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span>
</pre>
<div class="variablelist">
<p class="title"><b></b></p>
<dl>
<dt><span class="term">Returns</span></dt>
<dd><p>
The result of calling <code class="computeroutput"><span class="identifier">name</span><span class="special">()</span></code> on the argument used to construct
the object.
</p></dd>
</dl>
</div>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="utility_and_infrastructure.boost_python_type_id_hpp.functions"></a><a class="link" href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.functions" title="Functions">Functions</a>
</h3></div></div></div>
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> <span class="keyword">operator</span><span class="special"><<(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span><span class="identifier">s</span><span class="special">,</span> <span class="identifier">type_info</span> <span class="keyword">const</span><span class="special">&</span><span class="identifier">x</span><span class="special">);</span>
</pre>
<div class="variablelist">
<p class="title"><b></b></p>
<dl>
<dt><span class="term">Effects</span></dt>
<dd><p>
Writes a description of the type described by to <code class="computeroutput"><span class="identifier">x</span></code>
into s.
</p></dd>
<dt><span class="term">Rationale</span></dt>
<dd><p>
Not every C++ implementation provides a truly human-readable <code class="computeroutput"><span class="identifier">type_info</span><span class="special">::</span><span class="identifier">name</span><span class="special">()</span></code>
string, but for some we may be able to decode the string and produce
a reasonable representation.
</p></dd>
<dt><span class="term">Note</span></dt>
<dd><p>
On some non-conforming C++ implementations, the code is not actually
as simple as described above; the semantics are adjusted to work
as-if the C++ implementation were conforming.
</p></dd>
</dl>
</div>
<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="identifier">type_info</span> <span class="identifier">type_id</span><span class="special">()</span>
</pre>
<div class="variablelist">
<p class="title"><b></b></p>
<dl>
<dt><span class="term">Returns</span></dt>
<dd><p>
<code class="computeroutput"><span class="identifier">type_info</span><span class="special">(</span><span class="keyword">typeid</span><span class="special">(</span><span class="identifier">T</span><span class="special">))</span></code>
</p></dd>
<dt><span class="term">Note</span></dt>
<dd><p>
On some non-conforming C++ implementations, the code is not actually
as simple as described above; the semantics are adjusted to work
as-if the C++ implementation were conforming.
</p></dd>
</dl>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="utility_and_infrastructure.boost_python_type_id_hpp.example"></a><a class="link" href="boost_python_type_id_hpp.html#utility_and_infrastructure.boost_python_type_id_hpp.example" title="Example">Example</a>
</h3></div></div></div>
<p>
The following example, though silly, illustrates how the type_id facility
might be used
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">python</span><span class="special">/</span><span class="identifier">type_id</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<span class="comment">// Returns true iff the user passes an int argument</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span>
<span class="keyword">bool</span> <span class="identifier">is_int</span><span class="special">(</span><span class="identifier">T</span> <span class="identifier">x</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">python</span><span class="special">::</span><span class="identifier">type_id</span><span class="special">;</span>
<span class="keyword">return</span> <span class="identifier">type_id</span><span class="special"><</span><span class="identifier">T</span><span class="special">>()</span> <span class="special">==</span> <span class="identifier">type_id</span><span class="special"><</span><span class="keyword">int</span><span class="special">>();</span>
<span class="special">}</span>
</pre>
</div>
</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 © 2002-2005, 2015 David Abrahams, Stefan Seefeld<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>
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