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

score 2 · Accepted Answer · edited May 23 '17 at 12:32

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'

score 0 · Answer 2 · answered Jul 09 '15 at 11:00

If you are using C++11, I suggest using regular expression.

#include <iostream>
#include <regex>
using namespace std;
int main() {
    regex re("^/([^\\s]*)\\s([^\\s]*)"); // 1st () captures
                                         // 90pv-RKSJ-UCS2C and 2nd () captures usecmap
    smatch sm;
    string s="/90pv-RKSJ-UCS2C usecmap";
    regex_match(s,sm,re);
    for(int i=0;i<sm.size();i++) {
        cout<<sm[i]<<endl;
    }
    string label=sm[1],token=sm[2];
    system("pause");
}

Extracting Values from string using spirit parser

2 Answers2

Demo