[Spirit-general] qi grammar: concatenate several vector<string>

[Roman N. <neu...@si...>]

Hello,

I've got a simple Qi grammar that's been all auto-rules until now.  
Current code is:

    optionline
        %=  optname
        >>  omit[*blank]
        >>  '='
        >>  omit[*blank]
        >>  optval
    ;
    optname %= bareword;
    optval  %= (qstring | bareword) % +blank >> eol;

    bareword %= lexeme[+(alnum | char_("-.,_$"))];
    qstring %= lexeme['"' > *~char_('"') > '"'];

    qi::rule<I, std::string()> optname;
    qi::rule<I, std::vector<std::string>()> optval;
    qi::rule<I, std::string()> qstring;
    qi::rule<I, std::string()> bareword;

I want to extend the grammar to support continuation lines in optval,
where a continuation line is a physical line (outside qstring) with
leading whitespace.

Tentative code:

    optval
        %=  ovline
        >>  *(omit[+blank] >> ovline)
    ;
    ovline
        %=  ((qstring | bareword) % +blank)
        >>  eol
    ;

    qi::rule<I, std::vector<std::string>()> ovline;

of course fails to compile, though I'm perplexed by the error:

.../boost_1_41_0/boost/spirit/home/support/attributes.hpp:409:
    error: No match for 'vector<string>::vector(string &)'

Is there a way to keep the grammar both simple (as in language) and free
of semantic actions?  If not, what's the most concise way to flatten the
ovlines' vector<string>s into a single vector<string> in optval?


-- 
Roman Neuhauser