我需要解析simple_expression ::= limit int_number (days | hours | minutes) 。我写代码的语法

struct Parser: grammar<std::string::const_iterator, boost::spirit::ascii::space_type>
{
public:
  Parser(ConditionTree& a_lTree):
    Parser::base_type(limit_expression),
    m_lTree(a_lTree)
  {
    using boost::spirit::qi::uint_;

    using boost::spirit::qi::_1;
    using boost::spirit::qi::_2;

    limit_expression = limit_days_operator | limit_hours_operator | limit_minutes_operator ;

    limit_days_operator = ( string("limit") > uint_ > string("days") )[ phoenix::bind( &ConditionTree::AddDaysLimitOperator, m_lTree, _2) ]  ;
    limit_hours_operator = ( string("limit") > uint_ > string("hours") )[ phoenix::bind( &ConditionTree::AddHoursLimitOperator, m_lTree, _2) ]  ;
    limit_minutes_operator = ( string("limit") > uint_ > string("minutes") )[ phoenix::bind( &ConditionTree::AddMinutesLimitOperator, m_lTree, _2) ] ;

    BOOST_SPIRIT_DEBUG_NODE(limit_expression);

    BOOST_SPIRIT_DEBUG_NODE(limit_days_operator);
    BOOST_SPIRIT_DEBUG_NODE(limit_hours_operator);
    BOOST_SPIRIT_DEBUG_NODE(limit_minutes_operator);
  }

  rule<std::string::const_iterator, boost::spirit::ascii::space_type> limit_expression;
  rule<std::string::const_iterator, boost::spirit::ascii::space_type> limit_days_operator;
  rule<std::string::const_iterator, boost::spirit::ascii::space_type> limit_hours_operator;
  rule<std::string::const_iterator, boost::spirit::ascii::space_type> limit_minutes_operator;

  ConditionTree& m_lTree;
}


void main()
{

  ConditionTree oTree;

  Parser parser(oTree);

  std::string strTest("limit5minutes");

  std::string::const_iterator it_begin(strTest.begin());
  std::string::const_iterator it_end(strTest.end());

  bool result = phrase_parse(it_begin, it_end, parser, space);
}

：但它不能与下面的2个错误编译/usr/include/boost/spirit/home/support/argument.hpp:103: ошибка: no matching function for call to 'assertion_failed(mpl_::failed************ (boost::spirit::result_of::get_arg<boost::fusion::vector1<unsigned int&>, 1>::index_is_out_of_bounds::************)())'

/usr/include/boost/spirit/home/phoenix/bind/detail/member_function_ptr.hpp:103: ошибка: invalid initialization of reference of type 'const unsigned int&' from expression of type 'mpl_::void_'

上线limit_days_operator = ( string("limit") > uint_ > string("days") )[ phoenix::bind( &ConditionTree::AddDaysLimitOperator, m_lTree, _2) ] ;

我tryed语义动作移动到uint_：

limit_days_operator = string("limit") > uint_ [ phoenix::bind( &ConditionTree::AddDaysLimitOperator, m_lTree, _1) ] > string("days")  ;
limit_hours_operator = string("limit") > uint_ [ phoenix::bind( &ConditionTree::AddHoursLimitOperator, m_lTree, _1) ] > string("hours")  ;

然后解析器读取正确limit5days ，但不能正确limit5minutes ，因为，因为我看到，它无法区别limit5days从limit5hours 。

有很多怎么回事。然而，当时我做了固定的小东西想读它，让它完整（SSCCE），它编译过： 住在Coliru

我这里简要阐明一些个别点：

在语义动作绑定表达式复制m_lTree的价值，这种方式可以发生变异的成员。 phx::ref在这里需要
预期点使它不可能成功解析其他什么比“天”的限制
用lit ，除非你真的想消耗字符串作为属性的值。更重要的是，只写"limit" >> uint_ >> "days" ，因为超载超载不休息

正如你已经注意到有反模式的数量在这个语法，使它复杂：

提高精神：“语义行为是邪恶的”？
所述参考型构件 m_lTree导致距作用和紧密耦合。

然而：

这一切都表示，我会通过简化的东西，避免语义动作 ，分离分析和评价。简单解析成一个Limit结构：

qi::rule<Iterator, ConditionTree::Limit(), Skipper> limit_expression;

limit_expression = "limit" >> qi::uint_ >> unit_;

处理而无需单独表达分支单元：

unit_.add("days",    ConditionTree::Limit::days)
         ("hours",   ConditionTree::Limit::hours)
         ("minutes", ConditionTree::Limit::minutes);

因为，现在，语法只是解析Limit对象，你可以做解析后评价原子：

ConditionTree::Limit limit;
if (phrase_parse(iter, end, parser, ascii::space, limit))
{
    AddLimit(oTree, limit);
}

分离评价分析，可以添加喜欢的东西

相同的表达的重复评估（不重复解析）
简化评估前的表达式树
评估前验证
调试

稍微更有趣的是，允许你写ApplyLimit在实用的风格，而不是突变的对象：

 ConditionTree ApplyLimit(ConditionTree const& ct, Limit limit) { return ct + limit; // do something here }

但最重要的是：它巨大的简化语法，并节省您的生活的时间是比较好，否则花

看到这个住在Coliru ，输出：

void AddLimit(ConditionTree&, ConditionTree::Limit): 5 minutes

清单

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

namespace qi    = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;

struct ConditionTree {
    struct Limit {
        unsigned value;
        enum unit_t { days, hours, minutes } unit;
    };

    friend void AddLimit(ConditionTree& ct, Limit limit) {
        std::cout << "AddLimit: " << limit.value;
        switch (limit.unit) {
            case Limit::days:    std::cout << " days\n"; break;
            case Limit::hours:   std::cout << " hours\n"; break;
            case Limit::minutes: std::cout << " minutes\n"; break;
        }
    }
};

BOOST_FUSION_ADAPT_STRUCT(ConditionTree::Limit, (unsigned,value)(ConditionTree::Limit::unit_t,unit))

template <typename Iterator = std::string::const_iterator, typename Skipper = ascii::space_type>
struct Parser: qi::grammar<Iterator, ConditionTree::Limit(), ascii::space_type>
{
    public:
        Parser() : Parser::base_type(limit_expression)
    {
        unit_.add("days", ConditionTree::Limit::days)
                 ("hours", ConditionTree::Limit::hours)
                 ("minutes", ConditionTree::Limit::minutes);

        limit_expression = "limit" >> qi::uint_ >> unit_;
    }

    qi::symbols<char, ConditionTree::Limit::unit_t> unit_;
    qi::rule<Iterator, ConditionTree::Limit(), Skipper> limit_expression;
};

int main()
{
    ConditionTree oTree;

    Parser<> parser;

    std::string strTest("limit5minutes");

    std::string::const_iterator iter(strTest.begin()), end(strTest.end());

    ConditionTree::Limit limit;
    if (phrase_parse(iter, end, parser, ascii::space, limit))
    {
        AddLimit(oTree, limit);
    }
}