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<html><head><meta content="text/html; charset=ISO-8859-1" http-equiv="content-type"><title>Using with C++</title></head><body><h1>Using Pyrex with C++</h1>This section describes some features of Pyrex that are designed to facilitate wrapping of libraries written in C++.<br><ul id="mozToc"><!--mozToc h2 1 h3 2--><li><a href="#mozTocId714434">Source Filenames</a></li><li><a href="#mozTocId758326">C++ Structs and Classes</a><ul><li><a href="#mozTocId52035">Inheritance</a></li><li><a href="#mozTocId470913">Instantiation</a></li><li><a href="#mozTocId84624">Disposal</a></li></ul></li><li><a href="#mozTocId214896">Overloaded Functions</a></li></ul><h2><a class="mozTocH2" name="mozTocId714434"></a>Source Filenames</h2>Pyrex source files that use C++ features should be named with an extension of "<span style="font-family: monospace;">.pyx+</span>". The corresponding generated C file will then have an extension of ".cpp", and should be compiled with a C++ compiler.<br><br>Note that this only applies to <span style="font-style: italic;">implementation</span> files, not definition files. Definition files should always have an extension of ".pxd", whether they use C++ features or not.<br><h2><a class="mozTocH2" name="mozTocId758326"></a>C++ Structs and Classes</h2>C++ structs and classes are declared using <span style="font-family: monospace;">cdef+ struct</span>, for example,<br><br><div style="margin-left: 40px;"><span style="font-family: monospace;">cdef extern from "somewhere.h":</span><br><br style="font-family: monospace;"><span style="font-family: monospace;"> cdef+ struct Shrubbery:</span><br><span style="font-family: monospace;"> __init__()</span><br style="font-family: monospace;"><span style="font-family: monospace;"> __init__(float width)</span><br style="font-family: monospace;"><span style="font-family: monospace;"> __init__(float width, int price)</span><br><span style="font-family: monospace;"> float width</span><br><span style="font-family: monospace;"> int height</span><br style="font-family: monospace;"><span style="font-family: monospace;"> void plant_with_rhododendrons(int howmany)</span><br></div><br>Some important things to note:<br><ul><li>All <span style="font-family: monospace;">cdef+ struct</span> declarations must appear inside a <span style="font-family: monospace;">cdef extern from</span> block.</li><li>In Pyrex, <span style="font-family: monospace;">struct</span> is used regardless of whether the type is declared as a "struct" or a "class" in C++.</li><li>Constructors are declared using the name <span style="font-family: monospace;">__init__</span>. There can be multiple constructors with different signatures. If no constructor is declared, a single constructor with no arguments is assumed.</li><li>Destructors are not declared in Pyrex.</li><li>Member functions are declared without "virtual", whether they are virtual in C++ or not.</li></ul>A whole <span style="font-family: monospace;">extern from</span> block can also be declared using<span style="font-family: monospace;"> cdef+</span> if desired. This can be convenient when declaring a number of C++ types at once.<br><br><div style="margin-left: 40px;"><span style="font-family: monospace;">cdef+ extern from "shrubbing.h":</span><br><br style="font-family: monospace;"><span style="font-family: monospace;"> struct Shrubbery:</span><br><span style="font-family: monospace;"> ...</span><br style="font-family: monospace;"></div><span style="font-family: monospace;"></span><br>The effect is the same as if <span style="font-family: monospace;">cdef+</span> had been used on all the contained struct declarations. Other declarations appearing in the block are treated as ordinary <span style="font-family: monospace;">cdef</span> declarations.<br><h3><a class="mozTocH3" name="mozTocId52035"></a>Inheritance</h3>A C++ struct may inherit from one or more base structs.<br><br><div style="margin-left: 40px;"><span style="font-family: monospace;">cdef+ extern from "shrubbing.h":</span><br><br style="font-family: monospace;"><span style="font-family: monospace;"> struct FancyShrubbery(Shrubbery):</span><br><span style="font-family: monospace;"> ...</span><br></div><h3><a class="mozTocH3" name="mozTocId470913"></a>Instantiation</h3>C++ structs can be instantiated using the <span style="font-family: monospace;">new</span> operator, similarly to C++.<br><br><div style="margin-left: 40px;"><span style="font-family: monospace;">cdef Shrubbery *sh1, *sh2, *sh3</span><br><span style="font-family: monospace;">sh1 = new </span><span style="font-family: monospace;">Shrubbery()</span><br><span style="font-family: monospace;">sh2 = new </span><span style="font-family: monospace;">Shrubbery(3.2)</span><br><span style="font-family: monospace;">sh3 = new </span><span style="font-family: monospace;">Shrubbery(4.3, 800)</span><br><span style="font-family: monospace;"></span></div><br>Note that parentheses are required even if there are no arguments.<br><h3><a class="mozTocH3" name="mozTocId84624"></a>Disposal</h3>The <span style="font-family: monospace;">del</span> statement can be applied to a pointer to a C++ struct to deallocate it. This is equivalent to <span style="font-family: monospace;">delete</span> in C++.<br><br><div style="margin-left: 40px;"><span style="font-family: monospace;">cdef Shrubbery *big_sh</span><br><span style="font-family: monospace;">big_sh = new </span><span style="font-family: monospace;">Shrubbery(42.0)</span><br><span style="font-family: monospace;">display_in_garden_show(big_sh)</span><br style="font-family: monospace;"><span style="font-family: monospace;">del big_sh</span><br></div><h2><a class="mozTocH2" name="mozTocId214896"></a>Overloaded Functions</h2>Apart
from the special case of C++ struct constructors, there is no special
support for dealing with overloaded functions in C++. You will need to
declare each version of the function with a different name in Pyrex and
use C name specifications to map them all to the same C++ name. For
example,<br><br><div style="margin-left: 40px;"><span style="font-family: monospace;">cdef extern from "shrubbing.h":</span><br style="font-family: monospace;"><br style="font-family: monospace;"><span style="font-family: monospace;"> void build_with_width "build_shrubbery" (float width)</span><br style="font-family: monospace;"><span style="font-family: monospace;"> void build_with_petunias "build_shrubbery" (int number_of_petunias)</span><br></div><br></body></html>
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