[Boost-users] [Spirit/Qi/Phoenix] non compiling rules...

Subject: [Boost-users] [Spirit/Qi/Phoenix] non compiling rules...
From: Francois Mauger (mauger_at_[hidden])
Date: 2013-12-12 08:37:11

Dear Boosters,

The following code is one of my first attempts to use Spirit/Qi.
For my education, I have tried 2 techniques to parse the simple 
"aaa=131;" string.
The first one (Block A) compiles and seems to output the expected result.
The second (B) does not compile with a huge massively templatized 
backtrace that I don't understand.
What is the difference between using online rules and
rule objects ? Is there a syntax error somewhere ?
I'm afraid the documentation and example are rather terse about the
syntax to be used here  when coupling Qi and Phoenix...

Many thanks for your help.

best regards
frc
--
<pre>
#include <iostream>
#include <string>
#include <vector>
// - Boost/Spirit
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>
int main( int argc_, char * argv_[])
{
   int error_code = EXIT_SUCCESS;
   using boost::spirit::qi::double_;
   using boost::spirit::qi::string;
   using boost::spirit::qi::lit;
   using boost::spirit::qi::lexeme;
   using boost::spirit::qi::phrase_parse;
   using boost::spirit::qi::_1;
   using boost::spirit::qi::as_string;
   using boost::spirit::ascii::space;
   using boost::spirit::ascii::char_;
   using boost::phoenix::ref;
   {  // Block A
     /// This compiles:
     std::string s = "aaa=131;";
     std::cout << "s: '" << s << "'" << std::endl;
     std::string::iterator strbegin = s.begin();
     std::vector<char> vkey;
     std::vector<char> vvalue;
     bool r = phrase_parse(
                           strbegin,
                           s.end(),
                           (+(char_ - '='))[boost::phoenix::ref(vkey) = 
boost::spirit::qi::_1 ]
                           >> '=' >> *space
                           >> lexeme[+(char_ - 
';')][boost::phoenix::ref(vvalue) = boost::spirit::qi::_1 ],
                           space
                           );
     if (r) {
       std::string key(vkey.begin(), vkey.end());
       std::string value(vvalue.begin(), vvalue.end());
       std::cout << "key   : '" << key << "'" << std::endl;
       std::cout << "value : '" << value << "'" << std::endl;
     }
   }
   { /// Block B
     /// This doesn't:
     std::string s = "aaa=131;";
     std::cout << "s: '" << s << "'" << std::endl;
     std::string::iterator strbegin = s.begin();
     std::vector<char> vkey;
     std::vector<char> vvalue;
     boost::spirit::qi::rule<std::string::iterator> key_rule   = +(char_ 
- '=');
     boost::spirit::qi::rule<std::string::iterator> value_rule = 
lexeme[+(char_ - ';')];
     bool r = phrase_parse(
                           strbegin,
                           s.end(),
                           key_rule[boost::phoenix::ref(vkey) = 
boost::spirit::qi::_1 ]
                           >> '=' >> *space
                           >> value_rule[boost::phoenix::ref(vvalue) = 
boost::spirit::qi::_1 ],
                           space
                           );
     if (r) {
       std::string key(vkey.begin(), vkey.end());
       std::string value(vvalue.begin(), vvalue.end());
       std::cout << "key   : '" << key << "'" << std::endl;
       std::cout << "value : '" << value << "'" << std::endl;
     }
   }
   return error_code;
}
</pre>
-- 
François Mauger