c++ - How do I suppress skipping in boost::spirit for parsing a quoted string? -

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• boost spirit skipper issues 1 answer

i'm trying implement simple parser using boost::spirit (among other things) accepts strings in double quotes, e.g. "hello, world". here's stripped down program illustrates issue:

#include <iostream> #include <boost/iostreams/filtering_stream.hpp> #include <boost/spirit/include/qi.hpp> #include <boost/spirit/include/support_istream_iterator.hpp>  namespace qi = boost::spirit::qi;  static void print(const std::vector<char>& v) {    std::cout << std::string(v.begin(), v.end()) << '\n'; }  template<typename iterator> class grammar : public qi::grammar<iterator, boost::spirit::ascii::space_type> {    typedef boost::spirit::ascii::space_type space_type;    qi::rule<iterator, space_type> start;    qi::rule<iterator, std::vector<char>()> string;    qi::rule<iterator, char()> unescapedchar;  public:    grammar() : grammar::base_type(start) {       start = string[&print];       string %= qi::lexeme['"' >> qi::no_skip[*unescapedchar] >> '"'];       unescapedchar %= qi::char_ - qi::lit('"');    } };  int main() {    const std::string s("\"how brown cow\"");    boost::iostreams::filtering_istream fs(boost::make_iterator_range(s.begin(), s.end()));;     typedef boost::spirit::istream_iterator iterator;    qi::phrase_parse(       iterator(fs), iterator(),       grammar<iterator>(),       boost::spirit::ascii::space);     return 0; } 

in program unescapedchar rule defines allowable characters within string (anything double quotes) , string rule kleene star of unescapedchar within double quotes.

the output of program when passed "how brown cow" (with quotes part of string) hownowbrowncow. std::vector<char> attribute of string missing spaces. want spaces in parsed result.

neither unescapedchar nor string rule declarations specify skip type. tried use lexeme , no_skip directives both individually , (as shown above). have tried boost 1.49 , boost 1.55. in each case output has no embedded spaces.

in actual parser want skip spaces, not within quoted strings. doing incorrectly?

i think problem input stream skipping whitespace

see http://en.cppreference.com/w/cpp/io/manip/skipws

adding

fs.unsetf(std::ios::skipws); 

fixes things

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