c++ - Specify a charset without intepreting ranges -

i'm quite puzzled parsing strings when have define in rule minus , minus character , not range of characters between 2 endpoints.

for example, when write rule percent encode string of characters write

*(bk::char_("a-za-z0-9-_.~") | '%' << bk::right_align(2, 0)[bk::upper[bk::hex]]); 

which means "letters, capital letters, digits, minus sign, underscore, dot , tilde", third minus sign create range between 9 , underscore or something, have put minus @ end bk::char_("a-za-z0-9_.~-").

it solves current problem 1 when input dynamic, user input, , minus sign means minus character?

how prevent spirit assign special meaning of possible characters?

edit001: resort more concrete example @sehe answer

void spirit_direct(std::vector<std::string>& result, const std::string& input, char const* delimiter) {     result.clear();     using namespace bsq;     if(!parse(input.begin(), input.end(), raw[*(char_ - char_(delimiter))] % char_(delimiter), result))         result.push_back(input); } 

in case want ensure minus treated minus , not range 1 alter code following (according @sehe proposal below).

void spirit_direct(std::vector<std::string>& result, const std::string&     input, char const* delimiter) {     result.clear();     bsq::symbols<char, bsq::unused_type> sym_;     std::string separators = delimiter;     for(auto ch : separators)     {         sym_.add(std::string(1, ch));     }     using namespace bsq;     if(!parse(input.begin(), input.end(), raw[*(char_ - sym_)] % sym_, result))         result.push_back(input); } 

which looks quite elegant. in case of using static constant rule guess can escape characters '\', square brackets meant 1 of "special" characters need escaped. why? meaning of []? there additional characters escape?

simple.

you devise , specify supported patterns user can supply meanings.

next,

• you write code transforms character-set (e.g. expand ranges (if supported in user input) , sort - first character definition).

• do not use character set @ all.

  • why not use char_ [ _pass = my_match_predicate(_1) ]
  • why not make alternation of literal characters? lit('a') | 'b' | '-' | '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'

  • why not use qi::symbols<char, char> (or qi::symbols<char, qi::unused_type> sym_; raw [ sym_ ] or similar)

    update qi::symbols<> approach surprisingly fast: live on coliru. had recent optimization job disappointed: see answer (under "spirit (trie)") – binary string hex c++

in general, don't know you're trying achieve, spirit not well-suited generating rules on fly. see of existing boost-spirit answers on site.