c++ - Order of semantic actions using Spirit (with Phoenix reference) -


i'm building parser execute commands user may enter on command line. first part of command module belongs to, second part module's function call.

attached first parser semantic action (with boost::phoenix::ref()) supposed store name of module in variable m_modulename. attached 2nd parser semantic action calls function printparameters former variable parameter.

#include <boost/spirit/include/phoenix_core.hpp> #include <boost/spirit/include/phoenix_operator.hpp> #include <boost/spirit/home/qi.hpp> #include <boost/bind.hpp>  #include <iostream> #include <string>  namespace qi  = boost::spirit::qi; namespace phoenix = boost::phoenix;   void printparameters(const std::string & module, const std::string & command) {     std::cout << "module name during parse: " << module << std::endl;     std::cout << "command name during parse: " << command << std::endl; }   template <typename iterator> struct mycommandparser : public qi::grammar<iterator> {     mycommandparser() : mycommandparser::base_type(start)     {         start = qi::as_string[+(~qi::char_(' '))][phoenix::ref(m_modulename) = qi::_1]         >> qi::as_string[+(~qi::char_('\n'))][boost::bind(&printparameters, m_modulename, ::_1)];     };      qi::rule<iterator> start;     std::string m_modulename; };   int main() {     mycommandparser<std::string::const_iterator> commandgrammar;      commandgrammar.m_modulename = std::string("initial_default");     std::cout << "module name before parsing: " << commandgrammar.m_modulename << std::endl;      std::string str("mod01 cmd02\n");     std::string::const_iterator first = str.begin();     std::string::const_iterator last = str.end();     qi::parse(first, last, commandgrammar);      std::cout << "module name after parsing: " << commandgrammar.m_modulename << std::endl; }

expected result: during first semantic action value of m_modulename should set mod01 should printed during printparameters function.

actual result (program output):

module name before parsing: initial_default module name during parse:  command name during parse:  cmd02 module name after parsing: mod01

while constructing minimal example noticed value of m_modulename empty during execution of parse function, although has been set "initial_default" beforehand.

can please explain going on here?

why value empty instead of being mod01?

you cannot mix boost bind/phoenix/lambda/qi/std placeholders.

in fact cannot use boost bind inside semantic action.

you want use use phoenix::bind qi::_1. aoh, , add phoenix::cref() around m_modulename.

other that, don't want use ugly semantic actions in case @ all:

simplified:

live on coliru

#include <boost/spirit/include/qi.hpp>  namespace qi = boost::spirit::qi;  int main() {     std::string const str("mod01 cmd02\n");     std::string modulename, command;     qi::parse(str.begin(), str.end(), +~qi::char_(' ') >> +~qi::char_('\n'), modulename, command);        std::cout << "module name after parsing: " << modulename << "\n";     std::cout << "command after parsing:     " << command    << "\n"; }

prints

module name after parsing: mod01 command after parsing:      cmd02

see boost_fusion_adapt_struct , boost/fusion/adapted/std_pair.hpp e.g. ways scale/automate


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