boost/python
2
0
Fork 0
mirror of https://github.com/boostorg/python.git synced 2026-02-02 09:02:15 +00:00
Code Issues Projects Releases Wiki Activity

Tutorial updates. Added virtual functions with default implementations and reshufled the overloading topics to discuss manual overloading first.

Browse Source 
[SVN r17597]
This commit is contained in:
Joel de Guzman
2003-02-23 02:23:15 +00:00
parent acdad5caf3
commit 2a530bb9d2
11 changed files with 447 additions and 264 deletions
Download Patch File Download Diff File Expand all files Collapse all files

87
doc/tutorial/doc/overloading.html
View File

@@ -3,8 +3,8 @@
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
<title>Overloading</title>
<link rel="stylesheet" href="theme/style.css" type="text/css">
<link rel="prev" href="default_arguments.html">
<link rel="next" href="object_interface.html">
<link rel="prev" href="call_policies.html">
<link rel="next" href="default_arguments.html">
</head>
<body>
<table width="100%" height="48" border="0" cellspacing="2">
@@ -20,59 +20,16 @@
<table border="0">
<tr>
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
<td width="30"><a href="default_arguments.html"><img src="theme/l_arr.gif" border="0"></a></td>
<td width="20"><a href="object_interface.html"><img src="theme/r_arr.gif" border="0"></a></td>
<td width="30"><a href="call_policies.html"><img src="theme/l_arr.gif" border="0"></a></td>
<td width="20"><a href="default_arguments.html"><img src="theme/r_arr.gif" border="0"></a></td>
</tr>
</table>
<p>
It was mentioned in passing in the previous section that
<tt>BOOST_PYTHON_FUNCTION_OVERLOADS</tt> and <tt>BOOST_PYTHON_FUNCTION_OVERLOADS</tt>
can also be used for overloaded functions and member functions with a
common sequence of initial arguments. Here is an example:</p>
<code><pre>
<span class=keyword>void </span><span class=identifier>foo</span><span class=special>()
{
/*...*/
}
</span><span class=keyword>void </span><span class=identifier>foo</span><span class=special>(</span><span class=keyword>bool </span><span class=identifier>a</span><span class=special>)
{
/*...*/
}
</span><span class=keyword>void </span><span class=identifier>foo</span><span class=special>(</span><span class=keyword>bool </span><span class=identifier>a</span><span class=special>, </span><span class=keyword>int </span><span class=identifier>b</span><span class=special>)
{
/*...*/
}
</span><span class=keyword>void </span><span class=identifier>foo</span><span class=special>(</span><span class=keyword>bool </span><span class=identifier>a</span><span class=special>, </span><span class=keyword>int </span><span class=identifier>b</span><span class=special>, </span><span class=keyword>char </span><span class=identifier>c</span><span class=special>)
{
/*...*/
}
</span></pre></code>
<p>
Like in the previous section, we can generate thin wrappers for these
overloaded functions in one-shot:</p>
<code><pre>
<span class=identifier>BOOST_PYTHON_FUNCTION_OVERLOADS</span><span class=special>(</span><span class=identifier>foo_overloads</span><span class=special>, </span><span class=identifier>foo</span><span class=special>, </span><span class=number>0</span><span class=special>, </span><span class=number>3</span><span class=special>)
</span></pre></code>
<p>
Then...</p>
<code><pre>
<span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=string>&quot;foo&quot;</span><span class=special>, </span><span class=identifier>foo</span><span class=special>, </span><span class=identifier>foo_overloads</span><span class=special>());
</span></pre></code>
<p>
Notice though that we have a situation now where we have a minimum of zero
(0) arguments and a maximum of 3 arguments.</p>
<a name="manual_wrapping"></a><h2>Manual Wrapping</h2><p>
It is important to emphasize however that <b>the overloaded functions must
have a common sequence of initial arguments</b>. Otherwise, our scheme above
will not work.</p>
<p>
The following illustrates an alternate scheme for manually wrapping an
overloaded member function instead of
<tt>BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS</tt>. Obviously, the same technique
can be applied to wrapping overloaded non- member functions.</p>
The following illustrates a scheme for manually wrapping an overloaded
member function or. Obviously, the same technique can be applied to
wrapping overloaded non- member functions. Take note that this scheme
applies to actual overloaded (member, non-member) functions as well as
(member, non-member) functions with default arguments.</p>
<p>
We have here our C++ classes:</p>
<code><pre>
@@ -113,33 +70,11 @@ With these in hand, we can proceed to define and wrap this for Python:</p>
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>&quot;f&quot;</span><span class=special>, </span><span class=identifier>fx3</span><span class=special>)
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>&quot;f&quot;</span><span class=special>, </span><span class=identifier>fx4</span><span class=special>)
</span></pre></code>
<p>
Actually, we can mix and match manual wrapping of overloaded functions and
automatic wrapping through <tt>BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS</tt> and
its sister, <tt>BOOST_PYTHON_FUNCTION_OVERLOADS</tt>. Since the first overload
has default arguments, we can use <tt>BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS</tt>
to automatically wrap the first three of the <tt>def</tt>s above and manually
wrap just the last. Here's how we'll do this:</p>
<code><pre>
<span class=identifier>BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS</span><span class=special>(</span><span class=identifier>xf_overloads</span><span class=special>, </span><span class=identifier>f</span><span class=special>, </span><span class=number>1</span><span class=special>, </span><span class=number>4</span><span class=special>)
</span></pre></code>
<p>
Create a member function pointers as above for both X::f overloads:</p>
<code><pre>
<span class=keyword>bool </span><span class=special>(</span><span class=identifier>X</span><span class=special>::*</span><span class=identifier>fx1</span><span class=special>)(</span><span class=keyword>int</span><span class=special>, </span><span class=keyword>double</span><span class=special>, </span><span class=keyword>char</span><span class=special>) = &amp;</span><span class=identifier>X</span><span class=special>::</span><span class=identifier>f</span><span class=special>;
</span><span class=keyword>int </span><span class=special>(</span><span class=identifier>X</span><span class=special>::*</span><span class=identifier>fx2</span><span class=special>)(</span><span class=keyword>int</span><span class=special>, </span><span class=keyword>int</span><span class=special>, </span><span class=keyword>int</span><span class=special>) = &amp;</span><span class=identifier>X</span><span class=special>::</span><span class=identifier>f</span><span class=special>;
</span></pre></code>
<p>
Then...</p>
<code><pre>
<span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=string>&quot;f&quot;</span><span class=special>, </span><span class=identifier>fx1</span><span class=special>, </span><span class=identifier>xf_overloads</span><span class=special>());
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>&quot;f&quot;</span><span class=special>, </span><span class=identifier>fx2</span><span class=special>)
</span></pre></code>
<table border="0">
<tr>
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
<td width="30"><a href="default_arguments.html"><img src="theme/l_arr.gif" border="0"></a></td>
<td width="20"><a href="object_interface.html"><img src="theme/r_arr.gif" border="0"></a></td>
<td width="30"><a href="call_policies.html"><img src="theme/l_arr.gif" border="0"></a></td>
<td width="20"><a href="default_arguments.html"><img src="theme/r_arr.gif" border="0"></a></td>
</tr>
</table>
<br>