###  | # Boost.Python ## Header <boost/python/args.hpp>

## Contents

Introduction
keyword-expressions
Classes
  class `arg`
    class `arg` synopsis
    class `arg` constructor
    class `arg` template `operator =`
Keyword-expression operator `,`
Functions (deprecated)
  `args(`...`)`
Example(s)

## Introduction

Supplies a family of overloaded functions for specifying argument keywords for wrapped C++ functions.

## keyword-expressions

A keyword-expression results in an object which holds a sequence of ntbses, and whose type encodes the number of keywords specified. The keyword-expression may contain default values for some or all of the keywords it holds

## Classes

### `class arg;`

The objects of class arg are keyword-expressions holding one keyword ( size one )

#### Class `arg` synopsis

    namespace boost { namespace python
    {
            struct arg
            {
              template <class T>
                      arg &operator = (T const &value);
              explicit arg (char const *name){elements[0].name = name;}
            };

    }}

#### Class `arg` constructor

    arg(char const* name);

Requires: The argument must be a ntbs.
Effects: Constructs an `arg` object holding a keyword with name `name`.

#### Class `arg` operator =

    template <class T> arg &operator = (T const &value);

Requires: The argument must convertible to python.
Effects: Assigns default value for the keyword.
Returns: Reference to `this`.

## Keyword-expression operator `,`

          keyword-expression operator , (keyword-expression, const arg &kw) const
          keyword-expression operator , (keyword-expression, const char *name) const;

Requires: The argument `name` must be a ntbs.
Effects: Extends the keyword-expression argument with one more keyword.
Returns: The extended keyword-expression.

## Functions (deprecated)

### `args(`...`)`

      unspecified1 args(char const*);
        unspecified2 args(char const*, char const*);
           .
           .
           .
        unspecifiedN args(char const*, char const*, ... char const*);

Requires: Every argument must be a ntbs.
Returns: an object representing a keyword-expression encapsulating the arguments passed.

## Example

    #include <boost/python/def.hpp>
    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 )
                );
    }

Revised 01 August, 2003

© Copyright Dave Abrahams 2002-2003.