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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<!-- Copyright David Abrahams 2006. Distributed under the Boost -->
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    <title>Boost.Python - &lt;boost/python/args.hpp&gt;</title>
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          <h1 align="center"><a href="../index.html">Boost.Python</a></h1>

          <h2 align="center">Header &lt;boost/python/args.hpp&gt;</h2>
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    <hr>

    <h2>Contents</h2>

    <dl class="page-index">
      <dt><a href="#introduction">Introduction</a></dt>

      <dt><a href="#keyword-expression"><i>keyword-expressions</i></a></dt>

      <dt><a href="#classes">Classes</a></dt>

      <dd>
        <dl class="page-index">
          <dt><a href="#arg-spec">class <code>arg</code></a></dt>

          <dd>
            <dl class="page-index">
              <dt><a href="#arg-synopsis">class <code>arg</code>
              synopsis</a></dt>

              <dt><a href="#arg-ctor">class <code>arg</code>
              constructor</a></dt>

              <dt><a href="#arg-operator">class <code>arg</code> template
              <code>operator =</code></a></dt>
            </dl>
          </dd>
        </dl>
      </dd>

      <dt><a href="#keyword-expression-operators"><i>Keyword-expression</i>
      operator <code>,</code></a></dt>

      <dt><a href="#functions">Functions (deprecated)</a></dt>

      <dd>
        <dl class="page-index">
          <dt><code><a href=
          "#args-spec">args</a>(</code>...<code>)</code></dt>
        </dl>
      </dd>

      <dt><a href="#examples">Example(s)</a></dt>
    </dl>
    <hr>

    <h2><a name="introduction"></a>Introduction</h2>

    <p>Supplies a family of overloaded functions for specifying argument
    keywords for wrapped C++ functions.</p>

    <h2><a name="keyword-expression"></a><i>keyword-expressions</i></h2>

    <p>A <b>keyword-expression</b> results in an object which holds a
    sequence of <a href="definitions.html#ntbs">ntbs</a>es, and whose type
    encodes the number of keywords specified. The <b>keyword-expression</b>
    may contain default values for some or all of the keywords it holds</p>

    <h2><a name="classes"></a>Classes</h2>

    <h3><a name="arg-spec"></a><code>class arg;</code></h3>

    <p>The objects of class arg are keyword-expressions holding one keyword (
    size one )</p>

    <h4><a name="arg-synopsis"></a>Class <code>arg</code> synopsis</h4>
<pre>
namespace boost { namespace python
{
        struct arg 
        {
          template &lt;class T&gt;
                  arg &amp;operator = (T const &amp;value);
          explicit arg (char const *name){elements[0].name = name;}
        };

}}
</pre>

    <h4><a name="arg-ctor"></a>Class <code>arg</code> constructor</h4>
<pre>
arg(char const* name);
</pre>

    <dl class="function-semantics">
      <dt><b>Requires:</b> The argument must be a <a href=
      "definitions.html#ntbs">ntbs</a>.</dt>

      <dt><b>Effects:</b> Constructs an <code>arg</code> object holding a
      keyword with name <code>name</code>.</dt>
    </dl>

    <h4><a name="arg-operator"></a>Class <code>arg</code> operator =</h4>
<pre>
template &lt;class T&gt; arg &amp;operator = (T const &amp;value);
</pre>

    <dl class="function-semantics">
      <dt><b>Requires:</b> The argument must convertible to python.</dt>

      <dt><b>Effects:</b> Assigns default value for the keyword.</dt>

      <dt><b>Returns:</b> Reference to <code>this</code>.</dt>
    </dl>

    <h2><a name="keyword-expression-operators"><i>Keyword-expression</i>
    operator <code>,</code></a></h2>
<pre>
      <i>keyword-expression</i> operator , (<i>keyword-expression</i>, const arg &amp;kw) const
      <i>keyword-expression</i> operator , (<i>keyword-expression</i>, const char *name) const;
</pre>

    <dl class="function-semantics">
      <dt><b>Requires:</b> The argument <code>name</code> must be a <a href=
      "definitions.html#ntbs">ntbs</a>.</dt>

      <dt><b>Effects:</b> Extends the <i>keyword-expression</i> argument with
      one more keyword.</dt>

      <dt><b>Returns:</b> The extended <i>keyword-expression</i>.</dt>
    </dl>

    <h2><font color="#7F7F7F"><a name="functions"></a>Functions
    (deprecated)</font></h2>

    <h3><a name="args-spec"></a><code><font color=
    "#7F7F7F">args</font>(</code>...<code>)</code></h3>
<pre>
<font color="#7F7F7F">  <i>unspecified1</i> args(char const*);
    <i>unspecified2</i> args(char const*, char const*);
       .
       .
       .
    <i>unspecifiedN</i> args(char const*, char const*, ... char const*);
</font>
</pre>

    <dl class="function-semantics">
      <dt><font color="#7F7F7F"><b>Requires:</b> Every argument must be a <a
      href="definitions.html#ntbs">ntbs</a>.</font></dt>

      <dt><font color="#7F7F7F"><b>Returns:</b> an object representing a <a
      href="#keyword-expression"><i>keyword-expression</i></a> encapsulating
      the arguments passed.</font></dt>
    </dl>

    <h2><a name="examples"></a>Example</h2>
<pre>
#include &lt;boost/python/def.hpp&gt;
using namespace boost::python;

int f(double x, double y, double z=0.0, double w=1.0);

BOOST_PYTHON_MODULE(xxx)
{
   def("f", f
            , ( arg("x"), "y", arg("z")=0.0, arg("w")=1.0 ) 
            );
}
</pre>

    <p>Revised 01 August, 2003</p>

    <p><i>&copy; Copyright <a href=
    "http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2002-2003.</i></p>
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