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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<meta name="generator" content="HTML Tidy, 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/make_function.hpp></title>
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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" alt=
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"C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
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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 <boost/python/make_function.hpp></h2>
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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>
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<dt><a href="#functions">Functions</a>
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<dd>
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<dl class="page-index">
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<dt><a href="#make_function-spec">make_function</a>
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<dt><a href="#make_constructor-spec">make_constructor</a>
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</dl>
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<dt><a href="#examples">Example</a>
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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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<p><code><a href="#make_function-spec">make_function</a>()</code> and
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<code><a href="#make_constructor-spec">make_constructor</a>()</code> are
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the functions used internally by <code>class_<>::<a href=
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"class.html#class_-spec-modifiers">def</a></code>, <code>class_<>::<a
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href="module.html#module-spec-modifiers">def</a></code>, and
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<code>class_<>::<a href=
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"class.html#class_-spec-modifiers">def_init</a></code> to produce Python
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callable objects which wrap C++ functions and member functions.
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<h2><a name="functions"></a>Functions</h2>
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<pre>
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<a name="make_function-spec">template <class F></a>
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objects::function* make_function(F f)</a>
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template <class F, class Policies>
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objects::function* make_function(F f, Policies const& policies)
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</pre>
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<dl class="function-semantics">
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<dt><b>Requires:</b> <code>F</code> is a function pointer or member
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function pointer type
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<dt><b>Effects:</b> Creates a Python callable object which, when called
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from Python, converts its arguments to C++ and calls <code>f</code>. If
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<code>F</code> is a pointer-to-member-function type, the target object of
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the function call (<code>*this</code>) will be taken from the first
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Python argument, and subsequent Python arguments will be used as the
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arguments to <code>f</code>. If <code>policies</code> are supplied, it
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must be a model of <a href="CallPolicies.html">CallPolicies</a>, and will
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be applied to the function as described <a href=
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"CallPolicies.html">here</a>.
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<dt><b>Returns:</b> A pointer convertible to <code>PyObject*</code> which
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refers to the new Python callable object.
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</dl>
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<pre>
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<a name=
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"make_constructor-spec">template <class T, class ArgList, class Generator>
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objects::function* make_constructor();</a>
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</pre>
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<dl class="make_constructor-semantics">
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<dt><b>Requires:</b> <code>T</code> is a class type. <code>ArgList</code>
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is an <a href="../../../mpl/doc/Sequences.html">MPL sequence</a> of C++
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argument types (<i>A1, A2,... AN</i>) such that if
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<code>a1, a2</code>... <code>aN</code> are objects of type
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<i>A1, A2,... AN</i> respectively, the expression <code>new
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Generator::apply<T>::type(a1, a2</code>... <code>aN</code>) is
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valid. Generator is a model of <a href=
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"HolderGenerator.html">HolderGenerator</a>.
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<dt><b>Effects:</b> Creates a Python callable object which, when called
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from Python, expects its first argument to be a Boost.Python extension
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class object. It converts its remaining its arguments to C++ and passes
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them to the constructor of a dynamically-allocated
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<code>Generator::apply<T>::type</code> object. The result is
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installed in the extension class object.
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<dt><b>Returns:</b> The new Python callable object
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</dl>
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<h2><a name="examples"></a>Example</h2>
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<p>C++ function exposed below returns a callable object wrapping one of two
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functions.
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<pre>
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#include <boost/python/make_function.hpp>
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#include <boost/python/module.hpp>
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char const* foo() { return "foo"; }
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char const* bar() { return "bar"; }
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PyObject* choose_function(bool selector)
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{
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if (selector)
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return boost::python::make_function(foo);
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else
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return boost::python::make_function(bar);
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}
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BOOST_PYTHON_MODULE_INIT(make_function_test)
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{
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module("make_function_test")
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.def("choose_function", choose_function);
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}
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</pre>
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It can be used this way in Python:
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<pre>
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>>> from make_function_test import *
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>>> f = choose_function(1)
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>>> g = choose_function(0)
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>>> f()
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'foo'
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>>> g()
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'bar'
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</pre>
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<p>
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
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14 February 2002 <!--webbot bot="Timestamp" endspan i-checksum="39359" -->
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<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave
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Abrahams</a> 2002. All Rights Reserved.</i>
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