[Boost-users] spirit::qi action with Variant

Subject: [Boost-users] spirit::qi action with Variant
From: LiuGuangBao (easyeagel_at_[hidden])
Date: 2010-06-30 21:11:33

Hello all,
I want to write a const-expression parser which calculate the result 
while parsing. When do it with double and int, I don't know how to do, 
my code like:

namespace b=boost;
namespace bs=boost::spirit;
namespace bsq=boost::spirit::qi;
namespace bp=boost::phoenix;

bsq::real_parser<double,bsq::strict_real_policies<double> > bnf_double;
bsq::int_parser<int, 8, 1, -1> bnf_int8;
bsq::int_parser<int, 10, 1, -1> bnf_int10;
bsq::int_parser<int, 16, 1, -1> bnf_int16;

template <typename Iterator>
struct const_expression: bsq::grammar<Iterator,b::variant<int,double>()>
{
     typedef b::variant<int,double> result_type;
     const_expression() : const_expression::base_type(rstart)
     {
         using bsq::_val;
         using bsq::_1;
         using bsq::_a;
         result_type result;
         rstart =
             bnf_double[_val=_1] >>
                 *(
                     bsq::lit('+') >> bnf_double[how to write here]
                 )
             | rint [_val=_1]
             ;

         rint =
             bsq::lit('0') >> bsq::char_("xX") >> bnf_int16[_val=_1]
             | bsq::lit('0') >> bnf_int8[_val=_1]
             | bnf_int10[_val=_1]
             ;
     }

     bsq::rule<Iterator, result_type()> rstart;
     bsq::rule<Iterator, int()> rint;
};

Thanks
yours