boost::spirit multiline comment parsing - how?

29 Apr 2003

      Hi!

While playing around with the examples of the spirit library
I feel like I missed some essential points.

The far goal I have is to parse a file
containing C/C++ comments and
assignments of the form
name = value;
where I drop the comments and store the assignments 
in a map<string, string>.

If You have done something similar,
please share Your knowledge with the rest of us.

Below is a modifed version of comments.cpp.
Here I only try to output any comment found while dropping 
the other stuff. 
Why does the parser drop stuff after the 1st assignment?

the output of the code is

Parsed C-comment successfully!
Matched (27) characters: "//test2
/* test1 */// test

Any help appreciated.
Also I would like not to gather all commenst in one string ...

--------
#include "boost/spirit.hpp"

#include <iterator>
#include <string>
#include <iostream>
#include <cassert>
#include <fstream>
#include <map>
#include <cassert>

///////////////////////////////////////////////////////////////////////////////
// actor called after successfully matching a single character
class actor_string
{
public:
    actor_string(std::string &rstr) :
        matched(rstr)
    {
    }

    void operator() (const char *pbegin, const char *pend) const
    {
        matched += std::string(pbegin, pend-pbegin);
    }

private:
    std::string &matched;
};

///////////////////////////////////////////////////////////////////////////////
// actor called after successfully matching a C++-comment
void actor_cpp (const char *pfirst, const char *plast)
{
  std::cerr << "Parsing C++-comment" << std::endl;
  std::cerr << "Matched (" << plast-pfirst << ") characters: ";

  char cbbuffer[128];

  strncpy(cbbuffer, pfirst, plast-pfirst);
  cbbuffer[plast-pfirst] = '\0';

  std::cerr << "\"" << cbbuffer << "\"" << std::endl;
}

///////////////////////////////////////////////////////////////////////////////
// main entry point
int main ()
{
  using namespace boost::spirit;  

/////////////////////////////////////////////////////////////////////////////

  char const* pCComment = "//test2\n/* test1 */\n\n// test\nalpha = 
3.0;\n\n// beta is soo important\nbeta=5.6;\n\n/* \n\nSometimes comments 
are\ngood since\nbeta = 4.5;\nis a good choice, too\n\n*/";

  typedef skipper_iteration_policy<>                  iter_policy_t;
  typedef scanner_policies<iter_policy_t>             scanner_policies_t;
  typedef scanner<char const*, scanner_policies_t>    phrase_scanner_t;

  rule<phrase_scanner_t> cpp_comment, ignored, all;

  cpp_comment =
    comment_p("/*", "*/")           // rule for C-comments
    |   comment_p("//")             // rule for C++ comments
    ;

  std::string comment_c;

  all =
    (
     *cpp_comment[actor_string(comment_c)]
     | 
     *anychar_p
     )
    ;

  ignored = (space_p | chlit<char>('\n'));

  parse_info<> result;

  result = parse (pCComment, all, space_p);
  if (result.hit)
    {
      std::cerr << "Parsed C-comment successfully!" << std::endl;
      std::cerr << "Matched (" << comment_c.size() << ") characters: ";
      std::cerr << "\"" << comment_c << "\"" << std::endl;
    }
  else
    {
      std::cerr << "Failed to parse C/C++-comment!" << std::endl;
    }

  std::cerr << std::endl;
}

Markus

-- 

Compile time analytic differentiation? 
Yes, at http://daixtrose.sourceforge.net/

boost::spirit multiline comment parsing - how?

Markus Werle