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92 lines
4.4 KiB
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92 lines
4.4 KiB
HTML
<html>
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<head>
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<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
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<title>Policies</title>
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<link rel="stylesheet" href="theme/style.css" type="text/css">
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<link rel="prev" href="renaming_and_excluding.html">
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</head>
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<body>
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<table width="100%" height="48" border="0" cellspacing="2">
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<tr>
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<td><img src="../../../../boost.png">
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</td>
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<td width="85%">
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<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Policies</b></font>
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</td>
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</tr>
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</table>
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<br>
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<table border="0">
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<tr>
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<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
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</tr>
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</table>
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<p>
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Even thought Pyste can identify various elements in the C++ code, like virtual
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member functions, attributes, and so on, one thing that it can't do is to
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guess the semantics of functions that return pointers or references. In this
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case, the user must manually specify the policy. Policies are explained in the
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<a href="../../doc/tutorial/doc/html/python/functions.html#python.call_policies">
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tutorial</a>.</p>
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<p>
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The policies in Pyste are named exactly as in <a href="../../index.html">
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Boost.Python</a>, only the syntax is
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slightly different. For instance, this policy:</p>
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<code><pre>
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<span class=identifier>return_internal_reference</span><span class=special><</span><span class=number>1</span><span class=special>, </span><span class=identifier>with_custodian_and_ward</span><span class=special><</span><span class=number>1</span><span class=special>, </span><span class=number>2</span><span class=special>> >()
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</span></pre></code>
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<p>
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becomes in Pyste: </p>
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<code><pre>
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<span class=identifier>return_internal_reference</span><span class=special>(</span><span class=number>1</span><span class=special>, </span><span class=identifier>with_custodian_and_ward</span><span class=special>(</span><span class=number>1</span><span class=special>, </span><span class=number>2</span><span class=special>))
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</span></pre></code>
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<p>
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The user can specify policies for functions and virtual member functions with
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the <tt>set_policy</tt> function:</p>
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<code><pre>
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<span class=identifier>set_policy</span><span class=special>(</span><span class=identifier>f</span><span class=special>, </span><span class=identifier>return_internal_reference</span><span class=special>())
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</span><span class=identifier>set_policy</span><span class=special>(</span><span class=identifier>C</span><span class=special>.</span><span class=identifier>foo</span><span class=special>, </span><span class=identifier>return_value_policy</span><span class=special>(</span><span class=identifier>manage_new_object</span><span class=special>))
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</span></pre></code>
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<table width="80%" border="0" align="center">
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<tr>
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<td class="note_box">
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<img src="theme/note.gif"></img> <b>What if a function or member function needs a policy and
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the user doesn't set one?</b><br><br> If a function needs a policy and one
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was not set, Pyste will issue a error. The user should then go in the
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interface file and set the policy for it, otherwise the generated cpp won't
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compile.
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</td>
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</tr>
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</table>
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<table width="80%" border="0" align="center">
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<tr>
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<td class="note_box">
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<img src="theme/note.gif"></img>
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Note that for functions that return <tt>const T&</tt>, the policy
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<tt>return_value_policy<copy_const_reference>()</tt> wil be used by default, because
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that's normally what you want. You can change it to something else if you need
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to, though.
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</td>
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</tr>
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</table>
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<table border="0">
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<tr>
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<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
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</tr>
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</table>
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<br>
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<hr size="1"><p class="copyright">Copyright © 2003 Bruno da Silva de Oliveira<br>Copyright © 2002-2003 Joel de Guzman<br><br>
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<font size="2">Permission to copy, use, modify, sell and distribute this document
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is granted provided this copyright notice appears in all copies. This document
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is provided "as is" without express or implied warranty, and with
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no claim as to its suitability for any purpose. </font> </p>
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</body>
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</html>
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