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Added return_by_value, enhanced data member support to handle constant members
[SVN r15935]
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‎doc/v2/reference.html‎

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p.c3 {font-style: italic}
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h1.c1 {text-align: center}
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</style>
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</style>
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</head>
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<body>
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<dd>
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<dl class="index">
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<dt><a href="object.html#object-spec">object</a></dt>
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</dl>
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</dd>
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</dl>
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</dd>
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</dl>
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</dd>
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</dd>
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</dl>
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</dd>
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<dt><a href="return_by_value.html">return_by_value.hpp</a></dt>
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<dd>
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<dl class="index">
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<dt><a href="return_by_value.html#classes">Classes</a></dt>
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<dd>
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<dl class="index">
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<dt><a href=
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"return_by_value.html#return_by_value-spec">return_by_value</a></dt>
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</dl>
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</dd>
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</dl>
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</dd>
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</dl>
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</dd>
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</dl>
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<p>Revised
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
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08 October, 2002 <!--webbot bot="Timestamp" endspan i-checksum="39359" -->
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15 October, 2002
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<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
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</p>
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<p class="c3">&copy; Copyright <a href=

‎doc/v2/return_by_value.html‎

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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta name="generator" content=
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"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<link rel="stylesheet" type="text/css" href="../boost.css">
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<title>Boost.Python - &lt;boost/python/return_by_value.hpp&gt;</title>
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</head>
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<body>
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<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
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"header">
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<tr>
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<td valign="top" width="300">
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<h3><a href="../../../../index.htm"><img height="86" width="277"
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alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
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</td>
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<td valign="top">
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<h1 align="center">Boost.Python</h1>
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<h2 align="center">Header
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&lt;boost/python/return_by_value.hpp&gt;</h2>
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</td>
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</tr>
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</table>
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<hr>
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<h2>Contents</h2>
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<dl class="page-index">
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<dt><a href="#classes">Classes</a></dt>
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<dd>
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<dl class="page-index">
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<dt><a href="#return_by_value-spec">Class
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<code>return_by_value</code></a></dt>
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<dd>
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<dl class="page-index">
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<dt><a href="#return_by_value-spec-synopsis">Class
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<code>return_by_value</code> synopsis</a></dt>
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<dt><a href="#return_by_value-spec-metafunctions">Class
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<code>return_by_value</code> metafunctions</a></dt>
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</dl>
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</dd>
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</dl>
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</dd>
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<dt><a href="#examples">Example</a></dt>
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</dl>
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<hr>
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<h2><a name="classes"></a>Classes</h2>
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<h3><a name="return_by_value-spec"></a>Class
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<code>return_by_value</code></h3>
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<p><code>return_by_value</code> is a model of <a href=
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"ResultConverter.html#ResultConverterGenerator-concept">ResultConverterGenerator</a>
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which can be used to wrap C++ functions returning any reference or value
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type such that the return value is copied into a new Python object.</p>
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<h4><a name="return_by_value-spec-synopsis"></a>Class
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<code>return_by_value</code> synopsis</h4>
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<pre>
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namespace boost { namespace python
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{
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struct return_by_value
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{
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template &lt;class T&gt; struct apply;
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};
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}}
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</pre>
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<h4><a name="return_by_value-spec-metafunctions"></a>Class
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<code>return_by_value</code> metafunctions</h4>
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<pre>
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template &lt;class T&gt; struct apply
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</pre>
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<dl class="metafunction-semantics">
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<dt><b>Returns:</b> <code>typedef <a href=
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"to_python_value.html#to_python_value-spec">to_python_value</a>&lt;T&gt;
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type;</code></dt>
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</dl>
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<h2><a name="examples"></a>Example</h2>
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<h3>C++ Module Definition</h3>
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<pre>
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#include &lt;boost/python/module.hpp&gt;
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#include &lt;boost/python/class.hpp&gt;
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#include &lt;boost/python/return_by_value.hpp&gt;
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#include &lt;boost/python/return_value_policy.hpp&gt;
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// classes to wrap
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struct Bar { };
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Bar global_bar;
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// functions to wrap:
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Bar b1();
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Bar&amp; b2();
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Bar const&amp; b3();
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// Wrapper code
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using namespace boost::python;
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template &lt;class R&gt;
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void def_void_function(char const* name, R (*f)())
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{
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def(name, f, return_value_policy&lt;return_by_value&gt;());
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}
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BOOST_PYTHON_MODULE(my_module)
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{
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class_&lt;Bar&gt;("Bar");
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def_void_function("b1", b1);
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def_void_function("b2", b2);
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def_void_function("b3", b3);
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}
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</pre>
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<h3>Python Code</h3>
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<pre>
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&gt;&gt;&gt; from my_module import *
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&gt;&gt;&gt; b = b1() # each of these calls
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&gt;&gt;&gt; b = b2() # creates a brand
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&gt;&gt;&gt; b = b3() # new Bar object
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</pre>
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<p>Revised
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
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15 October, 2002
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<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
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</p>
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<p><i>&copy; Copyright <a href=
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"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
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Reserved.</i></p>
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</body>
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</html>
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‎include/boost/python/data_members.hpp‎

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# include <boost/type_traits/transform_traits.hpp>
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# include <boost/type_traits/cv_traits.hpp>
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# include <boost/python/return_value_policy.hpp>
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# include <boost/python/copy_non_const_reference.hpp>
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# include <boost/python/return_by_value.hpp>
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# include <boost/python/object/function_object.hpp>
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# include <boost/python/arg_from_python.hpp>
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# include <boost/bind.hpp>
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template <class C, class D>
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object make_getter(D C::*pm)
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{
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typedef return_value_policy<copy_non_const_reference> default_policy;
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typedef return_value_policy<return_by_value> default_policy;
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return objects::function_object(
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::boost::bind(

‎include/boost/python/object/iterator.hpp‎

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# include <boost/python/class.hpp>
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# include <boost/python/object/class_detail.hpp>
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# include <boost/python/return_value_policy.hpp>
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# include <boost/python/copy_const_reference.hpp>
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# include <boost/python/return_by_value.hpp>
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# include <boost/python/object/function_object.hpp>
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# include <boost/python/handle.hpp>
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# include <boost/type.hpp>
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// iterators are copied, so we just replace the result_converter from
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// the default_iterator_call_policies with a permissive one which
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// always copies the result.
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struct default_iterator_call_policies
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: default_call_policies
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{
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struct result_converter
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{
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template <class R>
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struct apply
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{
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typedef to_python_value<R> type;
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};
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};
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};
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typedef return_value_policy<return_by_value> default_iterator_call_policies;
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// Instantiations of these are wrapped to produce Python iterators.
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template <class NextPolicies, class Iterator>

‎include/boost/python/return_by_value.hpp‎

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// Copyright David Abrahams 2002. Permission to copy, use,
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// modify, sell and distribute this software is granted provided this
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// copyright notice appears in all copies. This software is provided
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// "as is" without express or implied warranty, and with no claim as
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// to its suitability for any purpose.
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#ifndef BY_VALUE_DWA20021015_HPP
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# define BY_VALUE_DWA20021015_HPP
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# include <boost/python/to_python_value.hpp>
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# include <boost/type_traits/add_reference.hpp>
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# include <boost/type_traits/add_const.hpp>
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namespace boost { namespace python {
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struct return_by_value
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{
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template <class R>
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struct apply
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{
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typedef to_python_value<
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typename add_reference<
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typename add_const<R>::type
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>::type
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> type;
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};
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};
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}} // namespace boost::python
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#endif // BY_VALUE_DWA20021015_HPP

‎test/data_members.cpp‎

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// to its suitability for any purpose.
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#include <boost/python/class.hpp>
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#include <boost/python/module.hpp>
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#include <boost/python/return_value_policy.hpp>
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#include <boost/python/return_by_value.hpp>
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#include "test_class.hpp"
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double get_fair_value(X const& x) { return x.value(); }
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struct Var
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{
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Var(std::string name_) : name(name_), value(), name2(name.c_str()) {}
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std::string const name;
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std::string get_name1() const { return name; }
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std::string const& get_name2() const { return name; }
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float value;
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char const* name2;
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};
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BOOST_PYTHON_MODULE(data_members_ext)
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{
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class_<Var>("Var", init<std::string>())
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.def_readonly("name", &Var::name)
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.def_readonly("name2", &Var::name2)
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.def_readwrite("value", &Var::value)
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// Test return_by_value for plain values and for
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// pointers... return_by_value was implemented as a
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// side-effect of implementing data member support, so it made
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// sense to add the test here.
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.def("get_name1", &Var::get_name1, return_value_policy<return_by_value>())
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.def("get_name2", &Var::get_name2, return_value_policy<return_by_value>())
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;
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#include "module_tail.cpp"

‎test/data_members.py‎

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'''
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>>> from data_members_ext import *
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>>> y = Y(69)
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>>> y.x
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69
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>>> y.x = 77
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>>> y.x
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77
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>>> v = Var("pi")
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>>> v.value = 3.14
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>>> v.name
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'pi'
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>>> v.name2
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'pi'
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>>> v.get_name1()
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'pi'
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>>> v.get_name2()
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'pi'
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'''
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def run(args = None):

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