Re: index_is_out_of_bounds problem?

Hi Jens,

On 07/19/2016 08:09 PM, Jens Kallup wrote:
> Hello,
>
> I habe the following spirit grammar snippet:
> I don't know, why the error message index_out_of_bounds appears.
>
the count is off since you should not count the intervening character 
literals, which do not have an attribute (see 
http://www.boost.org/doc/libs/1_61_0/libs/spirit/doc/html/spirit/qi/reference/char/char.html)

> Can You Help
> Jens
>
>              rfc_header
>                  = tok.kw_http >> '/' >> double_
>                                >> ' ' >> int_
>                                >> ' ' >> tok.identifier
>                        [
>                        qi::_val = phx::construct<expression_ast>(
>                             std::string("header1")
>                            , qi::_3
>                            , qi::_5
>                            , qi::_7
these should be:
                             , qi::_2
                             , qi::_3
                             , qi::_4

>                            , qi::_val)

_val will not be set to the value you expect. It will hold the value due 
to the default constructor.

Have a look at the simple test program in the attachment. If you change
[ std::cout <<  _1 << " " << _2 << " " << _val << "\n" ]
to
[ std::cout <<  _1 << " " << _3 << " " << _val << "\n" ]
it will fail to compile.

Also examine that the the output due to '_val' is in a default 
constructed state (0 0).
With the semantic actions attached you can turn on attribute propagation 
by using the '%=' operator instead just '=' in the rule assignment (also 
see the small demo program if you change it to '=' again).

Cheers
	Philipp

>                        ]
>                  ;
>
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------------------------------------------------------------------------------
What NetFlow Analyzer can do for you? Monitors network bandwidth and traffic
patterns at an interface-level. Reveals which users, apps, and protocols are 
consuming the most bandwidth. Provides multi-vendor support for NetFlow, 
J-Flow, sFlow and other flows. Make informed decisions using capacity planning
reports.http://sdm.link/zohodev2dev

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

template<typename IteratorType, typename AttributeType>
struct simple_grammar
  : boost::spirit::qi::grammar<IteratorType, AttributeType()> {
  simple_grammar() :
    simple_grammar::base_type(start) {
    using namespace boost::spirit::qi ;
    start %= (double_ >> ' ' >> double_)
      // this one works
      [ std::cout <<  _1 << " " << _2 << " " << _val << "\n" ]
      // this is will not work
      // [ std::cout <<  _1 << " " << _3 << " " << _val << "\n" ]
      ;
  }
  typedef boost::spirit::qi::rule<IteratorType, AttributeType()> rule_type ;
  rule_type start ;
} ;


int main() {
  typedef std::string input_type ;
  typedef input_type::const_iterator iterator_type ;
  typedef boost::fusion::vector<double, double> attribute_type ;
  typedef simple_grammar<iterator_type, attribute_type> grammar_type ;

  input_type input("1 2") ;
  iterator_type iterator = input.begin() ;
  iterator_type finish = input.end() ;

  attribute_type result ;

  bool ret_val =
    boost::spirit::qi::parse(iterator, finish, grammar_type(), result) ;
    
  if (ret_val && (iterator == finish)) {
    std::cout << "successuflly parsed\n" ;
  } else {
    std::cout << "error parsing\n" ;
  }

  std::cout << result << "\n" ;
  return 0 ;
}