| 1 | <!-- Copyright David Abrahams 2006. Distributed under the Boost --> |
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| 2 | <!-- Software License, Version 1.0. (See accompanying --> |
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| 3 | <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) --> |
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| 4 | <html> |
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| 5 | <head> |
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| 6 | <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> |
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| 7 | <link rel="stylesheet" type="text/css" href=../../../../boost.css> |
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| 8 | <title>Boost.Python - Extractor Concept</title> |
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| 9 | </head> |
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| 10 | <body link="#0000ff" vlink="#800080"> |
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| 11 | <table border="0" cellpadding="7" cellspacing="0" width="100%" summary= |
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| 12 | "header"> |
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| 13 | <tr> |
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| 14 | <td valign="top" width="300"> |
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| 15 | <h3><a href="../../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../../boost.png" border="0"></a></h3> |
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| 16 | </td> |
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| 17 | <td valign="top"> |
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| 18 | <h1 align="center"><a href="../index.html">Boost.Python</a></h1> |
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| 19 | <h2 align="center">Extractor Concept</h2> |
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| 20 | </td> |
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| 21 | </tr> |
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| 22 | </table> |
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| 23 | <hr> |
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| 24 | <dl class="page-index"> |
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| 25 | <dt><a href="#introduction">Introduction</a></dt> |
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| 26 | <dt><a href="#concept-requirements">Concept Requirements</a></dt> |
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| 27 | <dl class="page-index"> |
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| 28 | <dt><a href="#Extractor-concept">Extractor Concept</a></dt> |
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| 29 | </dl> |
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| 30 | <dt><a href="#notes">Notes</a></dt> |
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| 31 | </dl> |
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| 32 | |
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| 33 | <h2><a name="introduction"></a>Introduction</h2> |
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| 34 | |
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| 35 | <p>An Extractor is a class which Boost.Python can use to extract C++ |
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| 36 | objects from Python objects, and is typically used by facilities that |
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| 37 | define <code>from_python</code> conversions for |
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| 38 | "traditional" Python extension types. |
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| 39 | |
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| 40 | <h2><a name="concept-requirements"></a>Concept Requirements</h2> |
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| 41 | <h3><a name="Extractor-concept"></a>Extractor Concept</h3> |
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| 42 | |
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| 43 | <p>In the table below, <code><b>X</b></code> denotes a model of |
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| 44 | Extractor and <code><b>a</b></code> denotes an instance of a Python |
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| 45 | object type. |
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| 46 | |
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| 47 | <table summary="Extractor expressions" border="1" cellpadding="5"> |
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| 48 | |
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| 49 | <tr> |
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| 50 | <td><b>Expression</b></td> |
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| 51 | <td><b>Type</b></td> |
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| 52 | <td><b>Semantics</b></td> |
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| 53 | </tr> |
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| 54 | |
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| 55 | <tr> |
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| 56 | <td valign="top"><code>X::execute(a)</code></td> |
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| 57 | <td>non-void |
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| 58 | <td>Returns the C++ object being extracted. The |
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| 59 | <code>execute</code> function must not be overloaded. |
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| 60 | </tr> |
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| 61 | |
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| 62 | <tr> |
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| 63 | <td valign="top"><code>&a.ob_type</code> |
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| 64 | <td><code><a |
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| 65 | href="http://www.python.org/doc/2.2/ext/dnt-type-methods.html">PyTypeObject</a>**</code> |
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| 66 | <td>Points to the <code>ob_type</code> field of an object which is |
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| 67 | layout-compatible with <code>PyObject</code> |
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| 68 | </tr> |
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| 69 | |
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| 70 | </tr> |
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| 71 | |
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| 72 | </table> |
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| 73 | |
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| 74 | <h2><a name="notes"></a>Notes</h2> |
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| 75 | |
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| 76 | Informally, an Extractor's <code>execute</code> member must be a |
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| 77 | non-overloaded static function whose single argument is a Python |
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| 78 | object type. Acceptable Python object types include those publicly (and |
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| 79 | unambiguously) derived from <code>PyObject</code>, and POD types which |
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| 80 | are layout-compatible with PyObject. |
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| 81 | |
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| 82 | <hr> |
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| 83 | <p>Revised |
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| 84 | <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> |
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| 85 | 13 November, 2002 |
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| 86 | <!--webbot bot="Timestamp" endspan i-checksum="39359" --> |
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| 87 | </p> |
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| 88 | <p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave |
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| 89 | Abrahams</a> 2002. </i> |
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| 90 | |
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| 91 | <p>Permission to copy, use, modify, sell |
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| 92 | and distribute this software is granted provided this copyright notice appears |
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| 93 | in all copies. This software is provided "as is" without express or implied |
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| 94 | warranty, and with no claim as to its suitability for any purpose. |
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| 95 | </body> |
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| 96 | </html> |
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