How to parse csv using boost::spirit

Question

I have this csv line

std::string s = R\"(1997,Ford,E350,\"ac, abs, moon\",\"some \"rusty\" parts\",3000.00)\";

I can parse it using

Answer 1

Sehe's post looks a fair bit cleaner than mine, but I was putting this together for a bit, so here it is anyways:

#include 
#include 

namespace qi = boost::spirit::qi;

int main() {
    const std::string s = R"(1997,Ford,E350,"ac, abs, moon",""rusty"",3000.00)";

    // Tokenizer
    typedef boost::tokenizer< boost::escaped_list_separator , std::string::const_iterator, std::string> Tokenizer;
    boost::escaped_list_separator seps('\\', ',', '\"');
    Tokenizer tok(s, seps);
    for (auto i : tok)
        std::cout << i << "\n";
    std::cout << "\n";

    // Boost Spirit Qi
    qi::rule quoted_string = '"' >> *(qi::char_ - '"') >> '"';
    qi::rule valid_characters = qi::char_ - '"' - ',';
    qi::rule item = *(quoted_string | valid_characters );
    qi::rule()> csv_parser = item % ',';

    std::string::const_iterator s_begin = s.begin();
    std::string::const_iterator s_end = s.end();
    std::vector result;

    bool r = boost::spirit::qi::parse(s_begin, s_end, csv_parser, result);
    assert(r == true);
    assert(s_begin == s_end);

    for (auto i : result)
        std::cout << i << std::endl;
    std::cout << "\n";
}   

And this outputs:

1997
Ford
E350
ac, abs, moon
rusty
3000.00

1997
Ford
E350
ac, abs, moon
rusty
3000.00

Something Worth Noting: This doesn't implement a full CSV parser. You'd also want to look into escape characters or whatever else is required for your implementation.

Also: If you're looking into the documentation, just so you know, in Qi, 'a' is equivalent to boost::spirit::qi::lit('a') and "abc" is equivalent to boost::spirit::qi::lit("abc").

On Double quotes: So, as Sehe notes in a comment above, it's not directly clear what the rules surrounding a "" in the input text means. If you wanted all instances of "" not within a quoted string to be converted to a ", then something like the following would work.

qi::rule double_quote_char = "\"\"" >> qi::attr('"');
qi::rule item = *(double_quote_char | quoted_string | valid_characters );