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| <h3><a href="../../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../../boost.png" border="0"></a></h3> |
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| <td valign="top"> |
| <h1 align="center"><a href="../index.html">Boost.Python</a></h1> |
| <h2 align="center">ResultConverter Concept</h2> |
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| <hr> |
| <dl class="page-index"> |
| <dt><a href="#introduction">Introduction</a></dt> |
| <dt><a href="#concept-requirements">Concept Requirements</a></dt> |
| <dd> |
| <dl class="page-index"> |
| <dt><a href="#ResultConverter-concept">ResultConverter Concept</a></dt> |
| <dt><a href="#ResultConverterGenerator-concept">ResultConverterGenerator Concept</a></dt> |
| </dl> |
| </dd> |
| </dl> |
| |
| <h2><a name="introduction"></a>Introduction</h2> |
| |
| <p>A ResultConverter for a type <code>T</code> is a type whose |
| instances can be used to convert C++ return values of type |
| <code>T</code> <code>to_python</code>. A ResultConverterGenerator is |
| an MPL unary metafunction class which, given the return type of a C++ |
| function, returns a ResultConverter for that type. ResultConverters in |
| Boost.Python generally inspect library's registry of converters to |
| find a suitable converter, but converters which don't use the registry |
| are also possible. |
| |
| <h2><a name="concept-requirements"></a>Concept Requirements</h2> |
| <h3><a name="ResultConverter-concept"></a>ResultConverter Concept</h3> |
| |
| <p>In the table below, <code><b>C</b></code> denotes a ResultConverter |
| type for a type <b><code>R</code></b> , <code><b>c</b></code> denotes |
| an object of type <code><b>C</b></code> , and <code><b>r</b></code> |
| denotes an object of type <code><b>R</b></code>. |
| |
| <table summary="ResultConverter expressions" border="1" cellpadding="5"> |
| |
| <tr> |
| <td><b>Expression</b></td> |
| <td><b>Type</b></td> |
| <td><b>Semantics</b></td> |
| </tr> |
| |
| <tr> |
| <td valign="top"><code>C c;</code></td> |
| <td> |
| <td>Constructs a <code>C</code> object. |
| </tr> |
| |
| <tr> |
| <td valign="top"><code>c.convertible()</code></td> |
| <td>convertible to <code>bool</code></td> |
| <td><code>false</code> iff no conversion from any <code>R</code> value |
| to a Python object is possible.</td> |
| </tr> |
| |
| <tr> |
| <td valign="top"><code>c(r)</code></td> |
| <td>convertible to <code>PyObject*</code></td> |
| <td>A pointer to a Python object corresponding to <code>r</code>, |
| or <code>0</code> iff <code>r</code> could not be converted |
| <code>to_python</code>, in which case <a |
| href="http://www.python.org/doc/current/api/exceptionHandling.html#l2h-71">PyErr_Occurred</a> |
| should return non-zero.</td> |
| </tr> |
| <tr> |
| <td valign="top"><code>c.get_pytype()</code></td> |
| <td><code>PyTypeObject const*</code></td> |
| <td>A pointer to a Python Type object corresponding to result of the conversion, |
| or <code>0</code>. Used for documentation generation. If <code>0</code> is returned |
| the generated type in the documentation will be <b>object</b> .</td> |
| </tr> |
| </table> |
| |
| <h3><a name="ResultConverterGenerator-concept"></a>ResultConverterGenerator Concept</h3> |
| <p>In the table below, <code><b>G</b></code> denotes a |
| ResultConverterGenerator type and <code><b>R</b></code> denotes a possible |
| C++ function return type. |
| |
| <table summary="ResultConverterGenerator expressions" border="1" cellpadding="5"> |
| <tr> |
| <td><b>Expression</b></td> |
| <td><b>Requirements</b></td> |
| </tr> |
| <tr> |
| <td valign="top"><code>G::apply<R>::type</code></td> |
| <td>A ResultConverter type for <code>R</code>.</td> |
| </table> |
| |
| <hr> |
| <p>Revised |
| <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> |
| 09 May, 2002 <!--Luann's birthday! --> |
| <!--webbot bot="Timestamp" endspan i-checksum="39359" --> |
| </p> |
| <p><i>© Copyright <a href="http://www.boost.org/people/dave_abrahams.htm">Dave |
| Abrahams</a> 2002. </i> |
| |
| <p>Permission to copy, use, modify, sell |
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