Attribute of qi parsers, C++ (vc++)

Attribute of qi parsers

#include <iostream>
#include <typeinfo>
#include <boost/spirit/include/qi.hpp>

template <typename Expr, typename Iterator = boost::spirit::unused_type>
struct attribute_of_qi_component
{
    typedef typename boost::spirit::result_of::compile<
        boost::spirit::qi::domain, Expr
    >::type parser_expression_type;
    typedef typename boost::spirit::traits::attribute_of<
        parser_expression_type, 
        boost::spirit::unused_type, Iterator
    >::type type;
};

struct string{};

template <typename Parser>
void print_attribute(const std::string& parser_text,Parser)
{
    std::cout << "------------------------------------------------------------------------------------\n";
    std::cout << "Attribute of: \"" << parser_text << "\"" << std::endl;
    std::cout << typeid(typename attribute_of_qi_component<Parser>::type).name() << std::endl;
}

#define IM_LAZY_MACRO(PARSER) #PARSER,PARSER

int main()
{
    using boost::spirit::qi::char_;
    using boost::spirit::qi::attr;
    using boost::spirit::qi::lit;
    boost::spirit::qi::rule<std::string::const_iterator,string()> type,delimiter,name;
    boost::spirit::qi::rule<std::string::const_iterator,uint32_t()> length;
    
    
    print_attribute(IM_LAZY_MACRO(
            lit("record")
            >>  char_('{')
            >>  type
            >>  delimiter 
            >>  length
            >>  name
            >>  char_('}')
    ));
    print_attribute(IM_LAZY_MACRO(
            lit("record")
            >>  lit('{')
            >>  type
            >>  delimiter 
            >>  length
            >>  name
            >>  lit('}')
    ));
    
    print_attribute(IM_LAZY_MACRO(
            lit("record")
            >>  lit('{')
            >>  type
            >>  (delimiter | attr("")) >> (length | attr(0))
            >>  name
            >>  lit('}')
    ));

print_attribute(IM_LAZY_MACRO(
            lit("record")
            >>  lit('{')
            >>  type
            >>  (delimiter | attr(string())) >> (length | attr(uint32_t(0)))
            >>  name
            >>  lit('}')
    ));
}


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