| 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 - ResultConverter 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">ResultConverter 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="#ResultConverter-concept">ResultConverter Concept</a></dt> |
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| 29 | <dt><a href="#ResultConverterGenerator-concept">ResultConverterGenerator Concept</a></dt> |
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| 30 | </dl> |
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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>A ResultConverter for a type <code>T</code> is a type whose |
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| 36 | instances can be used to convert C++ return values of type |
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| 37 | <code>T</code> <code>to_python</code>. A ResultConverterGenerator is |
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| 38 | an MPL unary metafunction class which, given the return type of a C++ |
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| 39 | function, returns a ResultConverter for that type. ResultConverters in |
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| 40 | Boost.Python generally inspect library's registry of converters to |
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| 41 | find a suitable converter, but converters which don't use the registry |
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| 42 | are also possible. |
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| 43 | |
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| 44 | <h2><a name="concept-requirements"></a>Concept Requirements</h2> |
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| 45 | <h3><a name="ResultConverter-concept"></a>ResultConverter Concept</h3> |
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| 46 | |
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| 47 | <p>In the table below, <code><b>C</b></code> denotes a ResultConverter |
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| 48 | type for a type <b><code>R</code></b> , <code><b>c</b></code> denotes |
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| 49 | an object of type <code><b>C</b></code> , and <code><b>r</b></code> |
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| 50 | denotes an object of type <code><b>R</b></code>. |
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| 51 | |
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| 52 | <table summary="ResultConverter expressions" border="1" cellpadding="5"> |
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| 53 | |
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| 54 | <tr> |
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| 55 | <td><b>Expression</b></td> |
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| 56 | <td><b>Type</b></td> |
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| 57 | <td><b>Semantics</b></td> |
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| 58 | </tr> |
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| 59 | |
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| 60 | <tr> |
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| 61 | <td valign="top"><code>C c;</code></td> |
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| 62 | <td> |
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| 63 | <td>Constructs a <code>C</code> object. |
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| 64 | </tr> |
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| 65 | |
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| 66 | <tr> |
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| 67 | <td valign="top"><code>c.convertible()</code></td> |
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| 68 | <td>convertible to <code>bool</code></td> |
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| 69 | <td><code>false</code> iff no conversion from any <code>R</code> value |
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| 70 | to a Python object is possible.</td> |
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| 71 | </tr> |
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| 72 | |
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| 73 | <tr> |
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| 74 | <td valign="top"><code>c(r)</code></td> |
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| 75 | <td>convertible to <code>PyObject*</code></td> |
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| 76 | <td>A pointer to a Python object corresponding to <code>r</code>, |
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| 77 | or <code>0</code> iff <code>r</code> could not be converted |
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| 78 | <code>to_python</code>, in which case <a |
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| 79 | href="http://www.python.org/doc/current/api/exceptionHandling.html#l2h-71">PyErr_Occurred</a> |
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| 80 | should return non-zero.</td> |
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| 81 | </tr> |
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| 82 | </table> |
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| 83 | |
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| 84 | <h3><a name="ResultConverterGenerator-concept"></a>ResultConverterGenerator Concept</h3> |
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| 85 | <p>In the table below, <code><b>G</b></code> denotes a |
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| 86 | ResultConverterGenerator type and <code><b>R</b></code> denotes a possible |
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| 87 | C++ function return type. |
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| 88 | |
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| 89 | <table summary="ResultConverterGenerator expressions" border="1" cellpadding="5"> |
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| 90 | <tr> |
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| 91 | <td><b>Expression</b></td> |
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| 92 | <td><b>Requirements</b></td> |
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| 93 | </tr> |
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| 94 | <tr> |
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| 95 | <td valign="top"><code>G::apply<R>::type</code></td> |
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| 96 | <td>A ResultConverter type for <code>R</code>.</td> |
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| 97 | </table> |
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| 98 | |
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| 99 | <hr> |
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| 100 | <p>Revised |
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| 101 | <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> |
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| 102 | 09 May, 2002 <!--Luann's birthday! --> |
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| 103 | <!--webbot bot="Timestamp" endspan i-checksum="39359" --> |
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| 104 | </p> |
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| 105 | <p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave |
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| 106 | Abrahams</a> 2002. </i> |
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| 107 | |
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| 108 | <p>Permission to copy, use, modify, sell |
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| 109 | and distribute this software is granted provided this copyright notice appears |
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| 110 | in all copies. This software is provided "as is" without express or implied |
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| 111 | warranty, and with no claim as to its suitability for any purpose. |
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| 112 | </body> |
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| 113 | </html> |
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