Re: [Spirit-general] A clean way to get attribute and raw string from a numeric parser?

[OvermindDL1 <ove...@gm...>]

On Thu, Jul 29, 2010 at 7:37 PM, Carl Barron <cba...@ro...> wrote:
>
> On Jul 29, 2010, at 9:18 PM, Joel de Guzman wrote:
>
>> On 7/29/2010 10:46 AM, Keith Rothman wrote:
>>> I am trying to get both the attribute (in this case double) and the raw string
>>> from a double_.
>>>
>>> I have something that works but it is "ugly" and uses grammar level state:
>>>
>>> #include<boost/config/warning_disable.hpp>
>>> #include<boost/spirit/include/qi.hpp>
>>> #include<boost/spirit/include/phoenix.hpp>
>>>
>>> #include<string>
>>>
>>> namespace client
>>> {
>>>
>>>      namespace qi = boost::spirit::qi;
>>>      struct double_str
>>>      {
>>>              double_str() {};
>>>              template<typename T>
>>>              double_str(double d, const T&  i) : d(d), str(i.begin(), i.end()) {};
>>>              double d;
>>>              std::string str;
>>>      };
>>>
>>>      template<typename Iterator>
>>>      struct grammer : qi::grammar<Iterator, double_str()>
>>>      {
>>>              double tmp;
>>>
>>>              grammer() : grammer::base_type(val, "val")
>>>              {
>>>                      using qi::double_;
>>>                      using qi::_val;
>>>                      using qi::_1;
>>>                      using qi::raw;
>>>                      namespace phx = boost::phoenix;
>>>
>>>                      val = raw[double_[ phx::ref(tmp) = _1] ][ _val = phx::construct<double_str>(
>>> phx::ref(tmp), _1 ) ];
>>>              }
>>>
>>>              qi::rule<Iterator, double_str()>  val;
>>>      };
>>> }
>>>
>>> int main(int argc, char *argv[])
>>> {
>>>      client::grammer<std::string::const_iterator>  gram;
>>>      std::string str("1e5");
>>>
>>>      std::string::const_iterator iter = str.begin();
>>>      std::string::const_iterator end = str.end();
>>>
>>>      client::double_str ds;
>>>
>>>      bool r = parse(iter, end, gram, ds);
>>> }
>>>
>>> Is there a cleaner way (no grammar level variable, or less semantic actions)?
>>
>> I'd use the same approach, but I'll adapt the double_str to fusion instead
>> and stuff the data directly. E.g. (using phoenix::at_c):
>>
>>     val = raw[double_[at_c<0>(_val) = _1] ]
>>         [at_c<0>(_val) = construct<std::string>(begin(_1), end(_1))];
>
>
>
>  1)  op %= instead of op =  eliminates the construction via phoenix.
>  now if you want the fusion sequeence <string,double>
>  2)    a simple start rule will produce it via attrib
>
>        start = val >> attrib(phx::ref(tmp);
>
>
>        so I'd keep the grammar and do 1 and 2,

Maybe even just this?
typedef boost::fusion::vector<std::string,double> str_double;
qi::rule<Iterator, str_double(), local<double> >  val;
val %= raw[double[_a = _1]] >> attr(_a);