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225 lines
6.3 KiB
HTML
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225 lines
6.3 KiB
HTML
Executable File
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<!-- Copyright David Abrahams 2006. Distributed under the Boost -->
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<!-- Software License, Version 1.0. (See accompanying -->
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<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
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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 Cygwin (vers 1st April 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 - <boost/python/return_arg.hpp></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="../../../../boost.png" border="0"></a></h3>
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</td>
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<td valign="top">
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<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
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<h2 align="center">Header <boost/python/return_arg.hpp></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="#introduction">Introduction</a></dt>
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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_arg-spec">Class Template
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<code>return_arg</code></a></dt>
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<dd>
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<dl class="page-index">
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<dt><a href="#return_arg-spec-synopsis">Class Template
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<code>return_arg</code> synopsis</a></dt>
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<dt><a href="#return_arg-spec-statics">Class
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<code>return_arg</code> static functions</a></dt>
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</dl>
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</dd>
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<dt><a href="#return_self-spec">Class Template
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<code>return_self</code></a></dt>
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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="introduction"></a>Introduction</h2>
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<code>return_arg</code> and <code>return_self</code> instantiations are
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models of <a href="CallPolicies.html">CallPolicies</a> which return the
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specified argument parameter (usually <code>*this</code>) of a wrapped
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(member) function.
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<h2><a name="classes"></a>Classes</h2>
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<h3><a name="return_arg-spec"></a>Class template
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<code>return_arg</code></h3>
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<table border="1" summary="return_arg template parameters">
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<caption>
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<b><code>return_arg</code> template parameters</b>
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</caption>
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<tr>
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<th>Parameter</th>
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<th>Requirements</th>
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<th>Description</th>
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<th>Default</th>
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</tr>
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<tr>
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<td><code>arg_pos</code></td>
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<td>A positive compile-time constant of type
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<code>std::size_t</code>.</td>
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<td>the position of the argument to be returned.</td>
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<td>1</td>
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</tr>
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<tr>
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<td><code>Base</code></td>
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<td>A model of <a href="CallPolicies.html">CallPolicies</a></td>
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<td>Used for policy composition. Any <code>result_converter</code> it
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supplies will be overridden by <code>return_arg</code>, but its
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<code>precall</code> and <code>postcall</code> policies are composed
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as described here <a href=
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"CallPolicies.html#composition">CallPolicies</a>.</td>
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<td><code><a href=
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"default_call_policies.html#default_call_policies-spec">default_call_policies</a></code></td>
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</tr>
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</table>
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<h4><a name="return_arg-spec-synopsis"></a>Class template
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<code>return_arg</code> synopsis</h4>
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<pre>
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namespace boost { namespace python
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{
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template <size_t arg_pos=1, class Base = default_call_policies>
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struct return_arg : Base
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{
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static PyObject* postcall(PyObject*, PyObject* result);
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struct result_converter{ template <class T> struct apply; };
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template <class Sig> struct extract_return_type : mpl::at_c<Sig, arg_pos>{};
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};
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}}
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</pre>
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<h4><a name="return_arg-spec-statics"></a>Class <code>return_arg</code>
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static functions</h4>
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<pre>
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PyObject* postcall(PyObject* args, PyObject* result);
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</pre>
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<dl class="function-semantics">
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<dt><b>Requires:</b> <code><a href=
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"http://www.python.org/doc/2.2/api/tupleObjects.html#l2h-476">PyTuple_Check</a>(args)
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!= 0</code> and <code>PyTuple_Size(args) != 0</code></dt>
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<dt><b>Returns:</b> <code>PyTuple_GetItem(args,arg_pos-1)</code></dt>
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</dl>
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<h3><a name="return_self-spec"></a>Class template
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<code>return_self</code></h3>
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<h4>Class template <code>return_self</code> synopsis:</h4>
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<pre>
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namespace boost { namespace python
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{
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template <class Base = default_call_policies>
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struct return_self
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: return_arg<1,Base>
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{};
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}}
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</pre>
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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 <boost/python/module.hpp>
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#include <boost/python/class.hpp>
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#include <boost/python/return_arg.hpp>
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struct Widget
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{
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Widget() :sensitive_(true){}
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bool get_sensitive() const { return sensitive_; }
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void set_sensitive(bool s) { this->sensitive_ = s; }
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private:
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bool sensitive_;
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};
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struct Label : Widget
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{
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Label() {}
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std::string get_label() const { return label_; }
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void set_label(const std::string &l){ label_ = l; }
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private:
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std::string label_;
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};
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using namespace boost::python;
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BOOST_PYTHON_MODULE(return_self_ext)
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{
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class_<widget>("Widget")
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.def("sensitive", &Widget::get_sensitive)
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.def("sensitive", &Widget::set_sensitive, return_self<>())
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;
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class_<Label, bases<Widget> >("Label")
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.def("label", &Label::get_label)
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.def("label", &Label::set_label, return_self<>())
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;
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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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>>> from return_self_ext import *
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>>> l1 = Label().label("foo").sensitive(false)
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>>> l2 = Label().sensitive(false).label("foo")
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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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19 July, 2003 <!--webbot bot="Timestamp" endspan i-checksum="39359" -->
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</p>
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<p><i>© Copyright <a href=
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"../../../../people/dave_abrahams.htm">Dave Abrahams</a> and Nikolay
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Mladenov 2003. </i></p>
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</body>
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</html>
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