[Boost-users] Spirit Newbie (balanced parentheses)

Subject: [Boost-users] Spirit Newbie (balanced parentheses)
From: EricB (eric.britz_at_[hidden])
Date: 2010-04-16 13:41:12

Hi all

I'm trying to use spirit in order to make a parser for a simple language.
Last time i had to do this I was in school (some more than 15 years ago).
I managed to do  something that works but it does not handle "balanced
parentheses".
I know this is a common problem but after having look for every possible
way of spelling "balanced parentheses" I did not find anything (that I
could understand).

The files I want to parse are made of ASCII char. They can contains
commands that should be interpreted (replacement).
Commands always start with "^!" (command switch).

An example of a file content:

        text text text ^!for-each( A )( B ) text text text text

I want to send the "text" strings to the std::cout and detect the
commands "^!for-each( A )( B )" in order to process them.
At the moment I only have one command "for-each"
Where:
A : is a query that can contain /'" and balanced ()
B : is the text to be sent to output for each result of the query. This
can be a 'script' meaning text + commands, for example:
        aa bb ^!for-each(C)(D) tt yy uu
therefore B can also contain balanced ().

The rules, I wrote does not handled balanced () very well.

For example the following command should be parsed successfully:

^!for-each( a/b/c()/e[]/d )
(
item [name] do ^!for-each(sub/text()) ( print() )
)

I need some advices. Thank you

So here are my rules
      {
          boost::spirit::chlit<>     LPAREN('(');
          boost::spirit::chlit<>     RPAREN(')');
          boost::spirit::strlit<>     CMDSWITCH("^!");

          script // main rule
            = * ( (boost::spirit::anychar_p - CMDSWITCH)
              | command
              );
          command
            = boost::spirit::discard_first_node_d[
              CMDSWITCH
              >> (for_each
                | boost::spirit::eps_p // for error reporting
              )
            ];
          for_each
            = boost::spirit::discard_first_node_d[
              boost::spirit::as_lower_d["for-each"]
                >> *boost::spirit::space_p
                >> query
                >> *boost::spirit::space_p
                >> subscript
            ];
          query
            = boost::spirit::inner_node_d[
              LPAREN >> *(boost::spirit::anychar_p - ( RPAREN )) >> RPAREN
            ];
          subscript
            = boost::spirit::inner_node_d[
              LPAREN >> *(
                (boost::spirit::anychar_p - ( CMDSWITCH | RPAREN ))
                |command
              ) >> RPAREN
            ];
        }