c++ - 使用 spirit 解析器从字符串中提取值

Question

我有以下行/90pv-RKSJ-UCS2C usecmap

std::string const line = "/90pv-RKSJ-UCS2C usecmap";

auto first = line.begin(), last = line.end();

std::string label, token;
bool ok = qi::phrase_parse(
        first, last, 
        qi::lexeme [ "/" >> +~qi::char_(" ") ] >> ' ' >>  qi::lexeme[+~qi::char_(' ')] , qi::space, label, token);


if (ok)
    std::cout << "Parse success: label='" << label << "', token='" << token << "'\n";
else
    std::cout << "Parse failed\n";

if (first!=last)
    std::cout << "Remaining unparsed input: '" << std::string(first, last) << "'\n";

我想在标签中90pv-RKSJ-UCS2C，在 token 变量中usecmap。

我提取了 90pv-RKSJ-UCS2C 值但没有使用 cmap

Answer 1

使用 space 作为 skipper ，你永远无法匹配 ' '(它被跳过了!)。另请参阅:Boost spirit skipper issues

所以，要么不使用 skipper ，要么让 skipper 吃掉它:

bool ok = qi::phrase_parse(
        first, last, 
        qi::lexeme [ "/" >> +qi::graph ] >> qi::lexeme[+qi::graph], qi::blank, label, token);

注意事项:

• 我使用了 qi::graph 而不是 ~qi::char_("") 公式

• 我使用blank_type 因为你说

  i have following line

  这意味着不应跳过行尾

演示

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#include <boost/spirit/include/qi.hpp>

namespace qi = boost::spirit::qi;

int main()
{
    std::string const line = "/90pv-rksj-ucs2c usecmap";

    auto first = line.begin(), last = line.end();

    std::string label, token;
    bool ok = qi::phrase_parse(
            first, last, 
            qi::lexeme [ "/" >> +qi::graph ] >> qi::lexeme[+qi::graph], qi::blank, label, token);

    if (ok)
        std::cout << "parse success: label='" << label << "', token='" << token << "'\n";
    else
        std::cout << "parse failed\n";

    if (first!=last)
        std::cout << "remaining unparsed input: '" << std::string(first, last) << "'\n";
}

打印:

parse success: label='90pv-rksj-ucs2c', token='usecmap'