精神real_parser ".e"

spirit real_parser ".e"

本文关键字：parser real 精神      更新时间：2023-10-16

我正在尝试使用real_parser和以下ureal_policies解析实数:

template <typename T>
struct number_real_policies : qi::ureal_policies<T>
{
    static bool const expect_dot = true;
    template <typename Iterator, typename Attribute>
    static bool
    parse_nan(Iterator& first, Iterator const& last, Attribute& attr) {
        return false;
    }
    template <typename Iterator, typename Attribute>
    static bool
    parse_inf(Iterator& first, Iterator const& last, Attribute& attr) {
        return false;
    }
};

它似乎完美地解析了我需要的所有实数格式的变化，但我注意到以下字符串也被接受:".12345.e12"。

小数点部分接受两个点是否正常(它只适用于E/E之前的第二个点，并且E/E必须存在)?

Thanks in advance

正如@llonesmiz在我的测试应用程序中正确指出的那样，它完全按照设计工作:

Live On Coliru

看起来你忘记检查解析器退出代码了?

#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/karma.hpp>
namespace qi    = boost::spirit::qi;
namespace karma = boost::spirit::karma;
typedef std::vector<double> attr_t;
template <typename T>
struct number_real_policies : qi::ureal_policies<T>
{
    static bool const expect_dot = true;
    template <typename Iterator, typename Attribute>
    static bool
    parse_nan(Iterator& first, Iterator const& last, Attribute& attr) {
        return false;
    }
    template <typename Iterator, typename Attribute>
    static bool
    parse_inf(Iterator& first, Iterator const& last, Attribute& attr) {
        return false;
    }
};
template <typename It, typename Skipper = qi::space_type>
    struct parser : qi::grammar<It, attr_t(), Skipper>
{
    parser() : parser::base_type(start)
    {
        using namespace qi;
        start %= *mydouble_;
        BOOST_SPIRIT_DEBUG_NODE(start);
    }
  private:
    qi::rule<It, attr_t(), Skipper> start;
    qi::real_parser<double, number_real_policies<double> > mydouble_;
};
bool doParse(const std::string& input)
{
    typedef std::string::const_iterator It;
    auto f(begin(input)), l(end(input));
    parser<It, qi::space_type> p;
    attr_t data;
    try
    {
        bool ok = qi::phrase_parse(f,l,p,qi::space,data);
        if (ok)   
        {
            std::cout << "parse successn";
            std::cout << "data: " << 
                karma::format_delimited(karma::columns(3) [*karma::auto_], ' ', data) << "n";
        }
        else      std::cerr << "parse failed: '" << std::string(f,l) << "'n";
        if (f!=l) std::cerr << "trailing unparsed: '" << std::string(f,l) << "'n";
        return ok;
    } catch(const qi::expectation_failure<It>& e)
    {
        std::string frag(e.first, e.last);
        std::cerr << e.what() << "'" << frag << "'n";
    }
    return false;
}
int main()
{
    bool ok = doParse(
            "0.    2.    .3    n  "
            "0.e7  2.e7  .3e7  n"
            "0.e-7 2.e-7 .3e-7 n"
            // shouldn't accept:
            //"0..e7n"
            "0.3.e7n"
            );
    return ok? 0 : 255;
}
输出:

parse success
data: 0.0 2.0 0.3 
0.0 2.0e07 3.0e06 
0.0 2.0e-07 3.0e-08 
0.3 
trailing unparsed: '.e7
'
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