RE: [boost] Boost.Spirit comments and stuff

From: Reece Dunn (msclrhd_at_[hidden])
Date: 2004-03-20 21:10:34

Hartmut Kaiser wrote:
>Reece Dunn wrote:

> > [4] I am now making use of boost::spirit::sub_grammar from
> > libs/spirit/doc/techniques.html. One thing I get from this is
> > that the typedef for the grammar type can be very difficult
> > to read, especially for non-trivial grammars! I have started
> > writing a set of type helpers to simplify the process:
>
>[snip]
>
> > If there is interest, I shall create a proper submission for them.
>
>Nice idea. Do you want to submit a patch for the
>libs/spirit/doc/techniques.html file?

I am not sure about a patch to the techniques.html file, maybe you or Joel 
want to add a comment. The idea was to have the type constructors as a 
helper file to be used in conjunction with sub_grammar, or when building any 
non-rule<> (explicitly typed) rule.

It contains some of the more common combinations, and can be used (using the 
skip_parser example) like:

   typedef boost::spirit::alternative_t
   <
      boost::spirit::space_parser,
      boost::spirit::line_comment,
      boost::spirit::range_comment
   >::type start_t;

Including the entire set into the HTML file would be too distracting. A link 
would probably be best with a few of the classes as an example.

NOTE: I have made a revision to alternative3_t so it is now a 2-4 -ary 
construct (it is easy to extend this to support more if there is a need) 
using mpl :). I have also added some more constructs that might be useful.

Here is a more complex example using my helpers:

      struct number_parser: public boost::spirit::sub_grammar< number_parser 
 >
      {
         public:
            typedef boost::spirit::contiguous_sequence_t
            <
               boost::spirit::alternative_t
               <
                  boost::spirit::sequence
                  <
                     boost::spirit::strlit_nocase_t<>::type,
                     boost::spirit::hex_t
                  >,
                  boost::spirit::sequence
                  <
                     boost::spirit::chlit<>,
                     boost::spirit::oct_t
                  >,
                  boost::spirit::real_t<>::type
               >::type,
               boost::spirit::kleene_star< 
boost::spirit::chset_nocase_t<>::type >
            >::type start_t;
         public:
            start_t                    start;
         public:
            inline           number_parser():
               start
               (
                  boost::spirit::lexeme_d
                  [
                     (
                        boost::spirit::as_lower_d[ "0x" ] >> 
boost::spirit::hex_p
                     |  '0' >> boost::spirit::oct_p
                     |  boost::spirit::real_p
                     )
                     >> *boost::spirit::as_lower_d[ boost::spirit::chset_p( 
"ldfu" )]
                  ]
               )
            {
            }
      } number;

Regards,
Reece

_________________________________________________________________
It's fast, it's easy and it's free. Get MSN Messenger today! 
http://www.msn.co.uk/messenger