## Listing built-in functionality

Raptor can be configured and compiled with support for different lists of parsers and serializers. The list built into the library can be found by means of description functions. These take as input an `int` counter and return descriptions of the object at that offset in the list. The return value is a pointer to a shared, read-only description of the object, or NULL if the counter has gone too far into the list.

Listing Functionality with Descriptions

Get descriptions of the parser syntaxes |
      const raptor_syntax_description*
      raptor_world_get_parser_description(raptor_world* world,
                                          unsigned int counter);
Get descriptions of the serializer syntaxes |
      const raptor_syntax_description*
      raptor_world_get_serializer_description(raptor_world* world,
                                              unsigned int counter);
Get descriptions of options |
      raptor_option_description*
      raptor_world_get_option_description(raptor_world* world,
                                          const raptor_domain domain,
                                          const raptor_option option);
Call with the appropriate domains for the class such as `RAPTOR_DOMAIN_PARSER`, `RAPTOR_DOMAIN_SERIALIZER` etc. See the `raptor_domain` description for the full list.

These functions can be called directly after creating a raptor world object with `raptor_new_world()`. This is one way to find a parser (name) by it's MIME Type, the other is to use the mime_type parameter of the `raptor_new_parser_for_content()`.

Example 1. List all parser options using option description

      unsigned int i;
      for(i = 0; i < raptor_option_get_count(); i++) {
        raptor_option_description* od;

        od = raptor_world_get_option_description(world, RAPTOR_DOMAIN_PARSER, i);

        if(od) {
          /* do something with od fields such as od->name, od->label */
        }
      }

There are more examples of this usage in the source for the `rapper` utility in `util/rapper.c`.