Extracting Values from string using spirit parser

Question

i have following line /90pv-RKSJ-UCS2C usecmap

std::string const line = "/90pv-RKSJ-UCS2C usecmap";

auto first = line.begin(), last = line.end();

std::string label, token;
bool ok = qi::phrase_parse(
        first, last, 
        qi::lexeme [ "/" >> +~qi::char_(" ") ] >> ' ' >>  qi::lexeme[+~qi::char_(' ')] , qi::space, label, token);


if (ok)
    std::cout << "Parse success: label='" << label << "', token='" << token << "'\n";
else
    std::cout << "Parse failed\n";

if (first!=last)
    std::cout << "Remaining unparsed input: '" << std::string(first, last) << "'\n";

I want to 90pv-RKSJ-UCS2C in label and usecmap in token variable.

I extract 90pv-RKSJ-UCS2C value but not usecmap

Answer 1

With space the skipper, you cannot ever match ' ' (it is skipped!). See also: Boost spirit skipper issues

So, either don't use a skipper, or allow the skipper to eat it:

bool ok = qi::phrase_parse(
        first, last, 
        qi::lexeme [ "/" >> +qi::graph ] >> qi::lexeme[+qi::graph], qi::blank, label, token);

Notes:

• I used qi::graph instead of the ~qi::char_(" ") formulation

• I used blank_type because you said

  i have following line

  Which implies that line-ends should not be skipped

Demo

Live On Coliru

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

namespace qi = boost::spirit::qi;

int main()
{
    std::string const line = "/90pv-rksj-ucs2c usecmap";

    auto first = line.begin(), last = line.end();

    std::string label, token;
    bool ok = qi::phrase_parse(
            first, last, 
            qi::lexeme [ "/" >> +qi::graph ] >> qi::lexeme[+qi::graph], qi::blank, label, token);

    if (ok)
        std::cout << "parse success: label='" << label << "', token='" << token << "'\n";
    else
        std::cout << "parse failed\n";

    if (first!=last)
        std::cout << "remaining unparsed input: '" << std::string(first, last) << "'\n";
}

Prints:

parse success: label='90pv-rksj-ucs2c', token='usecmap'