Question

我有以下boost :: spirit :: qi解析器规则：

namespace qi = boost::spirit::qi;
qi::rule<Iterator, BroadbandCurve(), Skipper> Cmd_BBNSET;


Cmd_BBNSET = +(qi::float_ >> qi::float_) >> qi::int_ >> qi::int_ >> lit("BBNSET");

我试图让它发出以下属性：

struct FreqLevelPair
{
    float freq;
    float dbLevel;
};
BOOST_FUSION_ADAPT_STRUCT(
    FreqLevelPair,
    (float, freq)
    (float, dbLevel)
)

struct BroadbandCurve
{
    std::vector<FreqLevelPair> freqPairs;
    int numFreqPairs; //Ignored since we can just count the number of pairs outright...
    int curveNum; //ID number
};
BOOST_FUSION_ADAPT_STRUCT(
    BroadbandCurve,
    (std::vector<FreqLevelPair>, freqPairs)
    (int, numFreqPairs)
    (int, curveNum)
)

正如你所看到的，我试图解析一对或多对浮点数，然后是两个整数，然后是文字“BBNSET”。所有这些代码都会编译，但是当我尝试解析格式的有效BBNSET命令时：

0.0 80.0 50.0 25.0 100.0 10.0 3 0 BBNSET

解析失败。我无法确定原因。我试图在lexeme指令中包装float对，并将+更改为a *，但无论我尝试了什么，该命令仍然无法解析，尽管编译没有问题。

我做错了什么，一旦正确解析，此规则会按预期发出属性吗？

Answer 1

我怀疑你的问题实际上与Recursive Descent Parsers有关。

Cmd_BBNSET = +(qi::float_ >> qi::float_) >> qi::int_ >> qi::int_ >> lit("BBNSET");

我们走吧：

0.0 80.0 50.0 25.0 100.0 10.0 3 0 BBNSET
^
Matches +(qi::float_ >> qi::float_)

0.0 80.0 50.0 25.0 100.0 10.0 3 0 BBNSET
         ^
         Matches +(qi::float_ >> qi::float_)

0.0 80.0 50.0 25.0 100.0 10.0 3 0 BBNSET
                   ^
                   Matches +(qi::float_ >> qi::float_)

0.0 80.0 50.0 25.0 100.0 10.0 3 0 BBNSET
                              ^
                          !!! Matches +(qi::float_ >> qi::float_) !!!

0.0 80.0 50.0 25.0 100.0 10.0 3 0 BBNSET
                                  ^
                                  Does not match qi::int_.

Answer 2

Sharth很快就注意到了原因。

解决方案，IMO将使用strict_real_policies

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#include <boost/fusion/adapted/struct.hpp>
#include <boost/spirit/include/qi.hpp>

namespace qi = boost::spirit::qi;

struct FreqLevelPair
{
    float freq;
    float dbLevel;
};

BOOST_FUSION_ADAPT_STRUCT(
    FreqLevelPair,
    (float, freq)
    (float, dbLevel)
)

struct BroadbandCurve
{
    std::vector<FreqLevelPair> freqPairs;
    int numFreqPairs; //Ignored since we can just count the number of pairs outright...
    int curveNum; //ID number
};

BOOST_FUSION_ADAPT_STRUCT(
    BroadbandCurve,
    (std::vector<FreqLevelPair>, freqPairs)
    (int, numFreqPairs)
    (int, curveNum)
)

int main()
{
    typedef std::string::const_iterator Iterator;
    typedef qi::space_type Skipper;

    qi::real_parser<double, qi::strict_real_policies<double> > strict_real_;

    qi::rule<Iterator, BroadbandCurve(), Skipper> Cmd_BBNSET;
    Cmd_BBNSET = +(strict_real_ >> strict_real_) >> qi::int_ >> qi::int_ >> qi::lit("BBNSET");

    std::string const input("0.0 80.0 50.0 25.0 100.0 10.0 3 0 BBNSET");
    auto f(input.begin()), l(input.end());
    bool ok = qi::phrase_parse(f, l, Cmd_BBNSET, qi::space);

    if (ok)
    {
        std::cout << "Parse succeeded\n";
    } else
    {
        std::cout << "Parse failed\n";
    }

    if (f!=l)
        std::cout << "Remaining unparsed: '" << std::string(f,l) << "'\n";
}

为什么没有这个提升:: spirit :: qi规则成功解析？

2 个答案: