Boost spirit get the whole match as a string

Question

I'm trying to define my own grammar using boost spirit framework and I'm defining such a matching rule:

value = (
        char_('"') >>
        (*qi::lexeme[
                char_('\\') >> char_('\\') |
                char_('\\') >> char_('"')  |
                graph - char_('"') |
                char_(' ')
        ])[some_func] >>
        char_('"')
);

I'd like to assing an action - some_func - to the part of it, and pass the whole matching string as a parameter. But unfortunately I will get something like vector<boost::variant<boost::fusion::vector2 ..a lot of stuff...)...> . Can I somehow get the whole data as a char*, std::string or even void* with size?

what is wrong with vector? – Öö Tiib Feb 21 '13 at 01:27 — Öö Tiib, Feb 21 '13 at 01:27
I describe it as a vector>>> but it was edited by sehe. – Dejwi Feb 21 '13 at 16:18 — Dejwi, Feb 21 '13 at 16:18

sehe · Accepted Answer · 2023-06-20T17:55:28.317

Look at qi::as_string:

Output of demo program:

DEBUG: 'some\\"quoted\\"string.'
parse success

To be honest, it looks like you are really trying to parse 'verbatim' strings with possible escape chars. In the respect, the use of lexeme seem wrong (the spaces get eaten). If you want to see samples of escaped string parsing, see e.g._

Boost Spirit Implement small one-line DSL on a server application (for this style)
Compiling a simple parser with Boost.Spirit (for escaping by duplication)
Parsing escaped strings with boost spirit
Parse quoted strings with boost::spirit

2023 UPDATE

Revisited this answer because of a broken link to liveworkspace.org, and in 2023 I'd write this like so:

A simple rearrangement that I think could be made, at least might look like:

template <typename It> struct parser : qi::grammar<It> {
    parser() : parser::base_type(value) {
        phx::function some_func = [](auto const& s) { //
            std::cout << "DEBUG: " << s << "\n";
        };

        value = qi::raw['"' >> *('\\' >> qi::char_ | ~qi::char_('"')) >> '"'][some_func(qi::_1)];
    }
  private:
    qi::rule<It> value;
};

Note that we simply declare the rule without a skipper and drop the lexeme (see Boost spirit skipper issues)

Live On Coliru

#include <boost/phoenix.hpp>
#include <boost/range/iterator_range_io.hpp>
#include <boost/spirit/include/qi.hpp>
#include <iomanip>

namespace qi  = boost::spirit::qi;
namespace phx = boost::phoenix;

template <typename It> struct parser : qi::grammar<It> {
    parser() : parser::base_type(value) {
        phx::function some_func = [](auto const& s) { //
            std::cout << "DEBUG: " << s << "\n";
        };

        value = qi::raw['"' >> *('\\' >> qi::char_ | ~qi::char_('"')) >> '"'][some_func(qi::_1)];
    }
  private:
    qi::rule<It> value;
};

bool doParse(std::string const& input) {
    typedef std::string::const_iterator It;
    auto f(begin(input)), l(end(input));

    try
    {
        parser<It> const p;

        bool ok = qi::phrase_parse(f, l, p, qi::space);
        if (ok)
            std::cout << "parse success\n";
        else
            std::cerr << "parse failed: " << quoted(std::string(f, l), '\'') << "\n";

        if (f!=l) std::cerr << "trailing unparsed: " << quoted(std::string(f,l), '\'') << "\n";
        return ok;
    } catch (qi::expectation_failure<It> const& e) {
        std::string frag(e.first, e.last);
        std::cerr << e.what() << quoted(frag, '\'') << "\n";
    }

    return false;
}

int main() {
    return doParse(R"("some \"quoted\" string.")") ? 0 : 255;
}

Prints

DEBUG: "some \"quoted\" string."
parse success

+1 I was going to answer with `as_string` earlier, but could not for the life of me find it in the docs – 'parser directives', duh! — ildjarn, Feb 21 '13 at 01:36
Added a concrete illustration of what would I think _needs_ to be fixed in the usage of `lexeme`. — sehe, Feb 21 '13 at 08:11

Boost spirit get the whole match as a string

1 Answers1

2023 UPDATE

Linked