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python/pyste/doc/templates.html
Dave Abrahams e70bbe4791 Fix license/copyright. 
Also port some "glaringly obvious" bugfixes from HEAD.  Hope it
doesn't cause problems.


[SVN r35237]
2006-09-20 22:49:18 +00:00

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<html>
<head>
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
<title>Templates</title>
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<td><img src="../../../../boost.png">
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<td width="85%">
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Templates</b></font>
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<p>
Template classes can easily be exported too, but you can't export the template
itself... you have to export instantiations of it! So, if you want to export a
<tt>std::vector</tt>, you will have to export vectors of int, doubles, etc.</p>
<p>
Suppose we have this code:</p>
<code><pre>
<span class=keyword>template </span><span class=special>&lt;</span><span class=keyword>class </span><span class=identifier>T</span><span class=special>&gt;
</span><span class=keyword>struct </span><span class=identifier>Point
</span><span class=special>{
</span><span class=identifier>T </span><span class=identifier>x</span><span class=special>;
</span><span class=identifier>T </span><span class=identifier>y</span><span class=special>;
};
</span></pre></code>
<p>
And we want to export <tt>Point</tt>s of int and double:</p>
<code><pre>
<span class=identifier>Point </span><span class=special>= </span><span class=identifier>Template</span><span class=special>(</span><span class=string>&quot;Point&quot;</span><span class=special>, </span><span class=string>&quot;point.h&quot;</span><span class=special>)
</span><span class=identifier>Point</span><span class=special>(</span><span class=string>&quot;int&quot;</span><span class=special>)
</span><span class=identifier>Point</span><span class=special>(</span><span class=string>&quot;double&quot;</span><span class=special>)
</span></pre></code>
<p>
Pyste will assign default names for each instantiation. In this example, those
would be &quot;<tt>Point_int</tt>&quot; and &quot;<tt>Point_double</tt>&quot;, but most of the time users will want to
rename the instantiations:</p>
<code><pre>
<span class=identifier>Point</span><span class=special>(</span><span class=string>&quot;int&quot;</span><span class=special>, </span><span class=string>&quot;IPoint&quot;</span><span class=special>) // </span><span class=identifier>renames </span><span class=identifier>the </span><span class=identifier>instantiation
</span><span class=identifier>double_inst </span><span class=special>= </span><span class=identifier>Point</span><span class=special>(</span><span class=string>&quot;double&quot;</span><span class=special>) // </span><span class=identifier>another </span><span class=identifier>way </span><span class=identifier>to </span><span class=keyword>do </span><span class=identifier>the </span><span class=identifier>same
</span><span class=identifier>rename</span><span class=special>(</span><span class=identifier>double_inst</span><span class=special>, </span><span class=string>&quot;DPoint&quot;</span><span class=special>)
</span></pre></code>
<p>
Note that you can rename, exclude, set policies, etc, in the <tt>Template</tt> object
like you would do with a <tt>Function</tt> or a <tt>Class</tt>. This changes affect all
<b>future</b> instantiations:</p>
<code><pre>
<span class=identifier>Point </span><span class=special>= </span><span class=identifier>Template</span><span class=special>(</span><span class=string>&quot;Point&quot;</span><span class=special>, </span><span class=string>&quot;point.h&quot;</span><span class=special>)
</span><span class=identifier>Point</span><span class=special>(</span><span class=string>&quot;float&quot;</span><span class=special>, </span><span class=string>&quot;FPoint&quot;</span><span class=special>) // </span><span class=identifier>will </span><span class=identifier>have </span><span class=identifier>x </span><span class=keyword>and </span><span class=identifier>y </span><span class=identifier>as </span><span class=identifier>data </span><span class=identifier>members
</span><span class=identifier>rename</span><span class=special>(</span><span class=identifier>Point</span><span class=special>.</span><span class=identifier>x</span><span class=special>, </span><span class=string>&quot;X&quot;</span><span class=special>)
</span><span class=identifier>rename</span><span class=special>(</span><span class=identifier>Point</span><span class=special>.</span><span class=identifier>y</span><span class=special>, </span><span class=string>&quot;Y&quot;</span><span class=special>)
</span><span class=identifier>Point</span><span class=special>(</span><span class=string>&quot;int&quot;</span><span class=special>, </span><span class=string>&quot;IPoint&quot;</span><span class=special>) // </span><span class=identifier>will </span><span class=identifier>have </span><span class=identifier>X </span><span class=keyword>and </span><span class=identifier>Y </span><span class=identifier>as </span><span class=identifier>data </span><span class=identifier>members
</span><span class=identifier>Point</span><span class=special>(</span><span class=string>&quot;double&quot;</span><span class=special>, </span><span class=string>&quot;DPoint&quot;</span><span class=special>) // </span><span class=identifier>also </span><span class=identifier>will </span><span class=identifier>have </span><span class=identifier>X </span><span class=keyword>and </span><span class=identifier>Y </span><span class=identifier>as </span><span class=identifier>data </span><span class=identifier>member
</span></pre></code>
<p>
If you want to change a option of a particular instantiation, you can do so:</p>
<code><pre>
<span class=identifier>Point </span><span class=special>= </span><span class=identifier>Template</span><span class=special>(</span><span class=string>&quot;Point&quot;</span><span class=special>, </span><span class=string>&quot;point.h&quot;</span><span class=special>)
</span><span class=identifier>Point</span><span class=special>(</span><span class=string>&quot;int&quot;</span><span class=special>, </span><span class=string>&quot;IPoint&quot;</span><span class=special>)
</span><span class=identifier>d_inst </span><span class=special>= </span><span class=identifier>Point</span><span class=special>(</span><span class=string>&quot;double&quot;</span><span class=special>, </span><span class=string>&quot;DPoint&quot;</span><span class=special>)
</span><span class=identifier>rename</span><span class=special>(</span><span class=identifier>d_inst</span><span class=special>.</span><span class=identifier>x</span><span class=special>, </span><span class=string>&quot;X&quot;</span><span class=special>) // </span><span class=identifier>only </span><span class=identifier>DPoint </span><span class=identifier>is </span><span class=identifier>affect </span><span class=identifier>by </span><span class=keyword>this </span><span class=identifier>renames</span><span class=special>,
</span><span class=identifier>rename</span><span class=special>(</span><span class=identifier>d_inst</span><span class=special>.</span><span class=identifier>y</span><span class=special>, </span><span class=string>&quot;Y&quot;</span><span class=special>) // </span><span class=identifier>IPoint </span><span class=identifier>stays </span><span class=identifier>intact
</span></pre></code>
<table width="80%" border="0" align="center">
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<td class="note_box">
<img src="theme/note.gif"></img> <b>What if my template accepts more than one type?</b>
<br><br>
When you want to instantiate a template with more than one type, you can pass
either a string with the types separated by whitespace, or a list of strings
(&quot;int double&quot; or [&quot;int&quot;, &quot;double&quot;] would both work).
</td>
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</table>
<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="policies.html"><img src="theme/l_arr.gif" border="0"></a></td>
<td width="20"><a href="wrappers.html"><img src="theme/r_arr.gif" border="0"></a></td>
</tr>
</table>
<br>
<hr size="1"><p class="copyright">Copyright &copy; 2003 Bruno da Silva de Oliveira<br>Copyright &copy; 2002-2003 Joel de Guzman<br><br>
<font size="2">Distributed under
the Boost Software License, Version 1.0. (See accompanying file
LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) </font> </p>
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