Define a Custom Attribute Mapping for a Generator

create_generator

The template create_generator is a type used as an customization point. It is invoked by the Karma create_generator API function in order to create a custom mapping of the given data type to a generator expression. This generator expression will be returned from create_generator whenever the given data type is encountered.

Module Headers

// forwards to <boost/spirit/home/karma/auto.hpp>
#include <boost/spirit/include/karma_auto.hpp>

Also, see Include Structure.

Namespace

Name
`boost::spirit::traits`

Synopsis

template <typename T, typename Enable>
struct create_generator
{
    typedef <unspecified> type;
    static type const& call();
};

Template parameters

Parameter	Description	Default
`T`	The type, `T` for which a custom mapping to a generator should be established.	none
`Enable`	Helper template parameter usable to selectively enable or disable certain specializations of `create_generator` utilizing SFINAE (i.e. `boost::enable_if` or `boost::disable_if`).	`void`

Notation

T: An arbitrary type.

Expression Semantics

Expression	Semantics
`create_generator<T>::type`	Defines the type of the generator expression returned from `call`.
`create_generator<T>::call()`	Returns a generator expression (usually this is a proto::expression) to be used as the default generator for the given type, `T`.

Predefined Specializations

Spirit predefines specializations of this customization point for several types. All predefined mappings are listed here: Additional Attribute Requirements for Generators.

	Note
	It is possible to overload the predefined mappings for the listed types by providing your own specialization of the `create_generator` customization point for the type to modify.

When to implement

The customization point create_generator needs to be implemented for a specific type whenever this type should be usable with the API function create_generator (which includes using the karma::auto_ generator and the special API functions based on the automatic creation of the matching generator type).

Example

For an example of how to use the customization point create_generator please see here: Example for Using the karma::auto_ Generator.