Question

我有以下代码：

#define BOOST_SPIRIT_DEBUG
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/include/io.hpp>
#include <boost/spirit/include/qi.hpp>

#include <iostream>
#include <string>
#include <vector>

struct parameter
{
  std::string type;
  std::string name;
};

BOOST_FUSION_ADAPT_STRUCT(
  parameter,
  (std::string, type)
  (std::string, name)
)

inline
std::ostream& operator<<(std::ostream& os, const parameter& param)
{
  os << param.type << ' ' << param.name;

  return os;
}

inline
std::ostream& operator<<(std::ostream& os, const std::vector<parameter>& parameters)
{
  for (const auto& param : parameters)
  {
    os << param;
  }

  return os;
}

struct function
{
  std::vector<parameter> parameters;
};

BOOST_FUSION_ADAPT_STRUCT(
  ::function,
  (std::vector<parameter>, parameters)
)

template <typename Iterator>
struct function_parser : boost::spirit::qi::grammar<Iterator, function(), boost::spirit::qi::ascii::space_type>
{
  function_parser() : function_parser::base_type(start)
  {
    using boost::spirit::qi::alnum;
    using boost::spirit::qi::alpha;

    string %= alpha >> *alnum;
    BOOST_SPIRIT_DEBUG_NODE(string);

    param %= string >> string;
    BOOST_SPIRIT_DEBUG_NODE(param);

    start %= *(param % ',');
    BOOST_SPIRIT_DEBUG_NODE(start);
  }

  boost::spirit::qi::rule<Iterator, std::string()> string;
  boost::spirit::qi::rule<Iterator, parameter, boost::spirit::qi::ascii::space_type> param;
  boost::spirit::qi::rule<Iterator, function(), boost::spirit::qi::ascii::space_type> start;
};

int main()
{
  std::string input_data("int bar, int baz");

  function fn;
  auto itr = input_data.begin();
  auto end = input_data.end();
  function_parser<decltype(itr)> g;
  bool res = boost::spirit::qi::phrase_parse(itr, end, g, boost::spirit::ascii::space, fn);
  if (res && itr == end)
  {
    std::cout << boost::fusion::tuple_open('[');
    std::cout << boost::fusion::tuple_close(']');
    std::cout << boost::fusion::tuple_delimiter(", ");

    std::cout << "Parsing succeeded \n";
    std::cout << "got: " << boost::fusion::as_vector(fn) << std::endl;
  }
  else
  {
    std::cout << "Parsing failed \n";
  }
}

输出

<start>
  <try>int bar, int baz</try>
  <param>
    <try>int bar, int baz</try>
    <string>
      <try>int bar, int baz</try>
      <success> bar, int baz</success>
      <attributes>[[i, n, t]]</attributes>
    </string>
    <string>
      <try>bar, int baz</try>
      <success>, int baz</success>
      <attributes>[[b, a, r]]</attributes>
    </string>
    <success>, int baz</success>
    <attributes>[]</attributes>
  </param>
  <param>
    <try> int baz</try>
    <string>
      <try>int baz</try>
      <success> baz</success>
      <attributes>[[i, n, t]]</attributes>
    </string>
    <string>
      <try>baz</try>
      <success></success>
      <attributes>[[b, a, z]]</attributes>
    </string>
    <success></success>
    <attributes>[]</attributes>
  </param>
  <param>
    <try></try>
    <string>
      <try></try>
      <fail/>
    </string>
    <fail/>
  </param>
  <success></success>
  <attributes>[[[]]]</attributes>
</start>
Parsing succeeded
got: []

解析成功后，为什么“got：”消息后没有列出任何参数？我做错了什么？

Answer 1

三个问题：

您在这里缺少括号：
```
boost::spirit::qi::rule<Iterator, parameter(), boost::spirit::qi::ascii::space_type> param;
                                           ^^
```
我同意，很难改进“迷路”模板参数的诊断并不容易。但是，这个是你很快习惯的东西，因为它是任何语法/规则定义的惯用语。
您的函数struct只包含一个元素，并且存在一些限制，即使用单元素元组“破坏”抽象。这是一个/非常知名/问题，应该在Spirit V3中得到缓解。现在，要么跳过结构：
```
using function = std::vector<parameter>;
```
或使用'规范'解决方法：
```
start %= eps >> (params % ',');
```
你的开始规则有一个假的kleen明星。如果要允许空参数列表，请执行
```
start %= eps >> -(params % ',');
```
完全不同（允许多个连续,：
```
start %= eps >> (-params % ',');
```
_{样式的剩余元素：%=在没有语义操作的规则上是多余的}

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输出：

<start>
  <try>int bar, int baz</try>
  <param>

    <!-- snip -->
    <attributes>[[[i, n, t], [b, a, z]]]</attributes>
  </param>
  <success></success>
  <attributes>[[[[[i, n, t], [b, a, r]], [[i, n, t], [b, a, z]]]]]</attributes>
</start>
Parsing succeeded 
got: [int bar; int baz; ]

完整代码

#define BOOST_SPIRIT_DEBUG
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/include/io.hpp>
#include <boost/spirit/include/qi.hpp>

#include <iostream>
#include <string>
#include <vector>

struct parameter
{
    std::string type;
    std::string name;
};

BOOST_FUSION_ADAPT_STRUCT(
    parameter,
    (std::string, type)
    (std::string, name)
)

inline std::ostream& operator<<(std::ostream& os, const parameter& param) { return os << param.type << ' ' << param.name;  }
inline std::ostream& operator<<(std::ostream& os, const std::vector<parameter>& parameters) {
  for (const auto& param : parameters) { os << param << "; "; }
  return os;
}

struct function
{
    std::vector<parameter> parameters;
};

BOOST_FUSION_ADAPT_STRUCT(
    ::function,
    (std::vector<parameter>, parameters)
)

template <typename Iterator>
struct function_parser : boost::spirit::qi::grammar<Iterator, function(), boost::spirit::qi::ascii::space_type>
{
    function_parser() : function_parser::base_type(start)
    {
        using boost::spirit::qi::alnum;
        using boost::spirit::qi::alpha;

        string %= alpha >> *alnum;
        BOOST_SPIRIT_DEBUG_NODE(string);

        param %= string >> string;
        BOOST_SPIRIT_DEBUG_NODE(param);

        start = boost::spirit::qi::eps >> (param % ',');
        BOOST_SPIRIT_DEBUG_NODE(start);
    }

    boost::spirit::qi::rule<Iterator, std::string()> string;
    boost::spirit::qi::rule<Iterator, parameter(), boost::spirit::qi::ascii::space_type> param;
    boost::spirit::qi::rule<Iterator, function(), boost::spirit::qi::ascii::space_type> start;
};

int main()
{
    std::string input_data("int bar, int baz");

    function fn;
    auto itr = input_data.begin();
    auto end = input_data.end();
    function_parser<decltype(itr)> g;
    bool res = boost::spirit::qi::phrase_parse(itr, end, g, boost::spirit::ascii::space, fn);
    if (res && itr == end)
    {
        std::cout << boost::fusion::tuple_open('[');
        std::cout << boost::fusion::tuple_close(']');
        std::cout << boost::fusion::tuple_delimiter(", ");

        std::cout << "Parsing succeeded \n";
        std::cout << "got: " << boost::fusion::as_vector(fn) << std::endl;
        //std::cout << "got: " << fn << std::endl;
    }
    else
    {
        std::cout << "Parsing failed \n";
    }
}

提升精神 - 无法获得属性

1 个答案:

完整代码