Question

我要做的是在运行时从ABNF语法文件创建解析器。我已经在qi :: grammar中实现了所有ABNF规则，就像这两个：

typedef /*qi::rule or struct containing qi::rule*/ parserRule

    [...] //all other ABNF rules according to RFC 5234

    rule =
            (
                    rulename[qi::_a = qi::_1] >>
                    definedAs >>
                    elements[qi::_b = qi::_1] >>
                    cNl
            )[qi::_val = px::bind(&AbnfParserFactory::fromRule, &factory, qi::_a, qi::_b)];


    rulelist =
            +(
                    rule[px::push_back(qi::_a, qi::_1)] |
                    (*cWsp >> cNl)
             ) >>
             eps[qi::_val = px::bind(&AbnfParserFactory::fromRulelist, &factory, qi::_a)];


qi::rule<Iterator, std::map<std::string, parserRule>(), qi::locals<std::vector<parserRule> > >  rulelist;
qi::rule<Iterator, parserRule(), qi::locals<std::string>, qi::locals<parserRule> >              rule;
[...] // all other ABNF rules

在ParserFactory内，根据读入的语法创建一个新的qi ::规则：

std::map<std::string, ReturnType> fromRulelist(std::vector<ReturnType> &rules)
{
    // return a map with <rulename, rule>
};

parserRule fromRule(std::string &name, parserRule &rule)
{
    //name the rule an return it
    rule.name(name);
    return rule;
};

问题是关于parserRule的类型。

如果我使用qi :: rule作为类型（就像我通常所希望的那样），我将丢失在ParserFactory中分配的每个规则名称（如fromRule中所示）。我猜这是由精神在内部工作的方式引起的（=运算符总是创建一个新的，未命名的规则。=用于分配px :: bind函数结果）

但是，如果我尝试将qi :: rule包装到结构中以避免此问题，我将无法再使用精灵调试来编译我的代码。这是我试过的：

typedef qi::rule<std::string::const_iterator, std::string()> FactoryRuleType;
struct parserRule
{
    FactoryRuleType mRule;
};

BOOST_FUSION_ADAPT_STRUCT(
 parserRule,
(FactoryRuleType, mRule)
)

[...] //rule definitions like above

debug(rule);
debug(rulelist);
[...] //debug all other rules

这会给我一大堆编译错误（这是很长的时间来发布）。我已经搜索了几天试图解决这个问题，但没有运气。我希望我提到足够的细节。

感谢任何帮助。

编译输出摘录：

/usr/include/boost/proto/operators.hpp:295:9: note:   template argument deduction/substitution failed:
/usr/include/boost/proto/operators.hpp: In substitution of ‘template<class Left, class Right> const typename boost::proto::detail::enable_binary<boost::proto::domainns_::deduce_domain, boost::proto::detail::not_a_grammar, boost::mpl::or_<boost::proto::is_extension<Arg>, boost::proto::is_extension<Right> >, boost::proto::tagns_::tag::shift_left, Left&, Right&>::type boost::proto::exprns_::operator<<(Left&, Right&) [with Left = std::basic_ostream<char>; Right = const boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, std::basic_string<char>()> >]’:
/usr/include/boost/spirit/home/support/attributes.hpp:1226:17:   required from ‘static void boost::spirit::traits::print_attribute_debug<Out, T, Enable>::call_impl3(Out&, const T_&, mpl_::false_) [with T_ = boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, std::basic_string<char>()> >; Out = std::basic_ostream<char>; T = boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, std::basic_string<char>()> >; Enable = void; mpl_::false_ = mpl_::bool_<false>]’
/usr/include/boost/spirit/home/support/attributes.hpp:1242:67:   required from ‘static void boost::spirit::traits::print_attribute_debug<Out, T, Enable>::call_impl2(Out&, const T_&, mpl_::false_) [with T_ = boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, std::basic_string<char>()> >; Out = std::basic_ostream<char>; T = boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, std::basic_string<char>()> >; Enable = void; mpl_::false_ = mpl_::bool_<false>]’
/usr/include/boost/spirit/home/support/attributes.hpp:1277:52:   required from ‘static void boost::spirit::traits::print_attribute_debug<Out, T, Enable>::call_impl(Out&, const T_&, mpl_::true_) [with T_ = boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, std::basic_string<char>()> >; Out = std::basic_ostream<char>; T = boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, std::basic_string<char>()> >; Enable = void; mpl_::true_ = mpl_::bool_<true>]’
/usr/include/boost/spirit/home/support/attributes.hpp:1283:52:   required from ‘static void boost::spirit::traits::print_attribute_debug<Out, T, Enable>::call(Out&, const T&) [with Out = std::basic_ostream<char>; T = boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, std::basic_string<char>()> >; Enable = void]’
/usr/include/boost/spirit/home/support/attributes.hpp:1303:53:   required from ‘void boost::spirit::traits::print_attribute(Out&, const T&) [with Out = std::basic_ostream<char>; T = boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, std::basic_string<char>()> >]’
/usr/include/boost/spirit/home/support/attributes.hpp:1196:57:   [ skipping 34 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
/usr/include/boost/function/function_template.hpp:722:7:   required from ‘boost::function4<R, T1, T2, T3, T4>::function4(Functor, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type) [with Functor = boost::spirit::qi::debug_handler<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, boost::spirit::context<boost::fusion::cons<FactoryReturnType&, boost::fusion::nil>, boost::fusion::vector0<> >, boost::spirit::unused_type, boost::spirit::qi::simple_trace>; R = bool; T0 = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >&; T1 = const __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >&; T2 = boost::spirit::context<boost::fusion::cons<FactoryReturnType&, boost::fusion::nil>, boost::fusion::vector0<> >&; T3 = const boost::spirit::unused_type&; typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type = int]’
/usr/include/boost/function/function_template.hpp:1069:16:   required from ‘boost::function<R(T0, T1, T2, T3)>::function(Functor, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type) [with Functor = boost::spirit::qi::debug_handler<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, boost::spirit::context<boost::fusion::cons<FactoryReturnType&, boost::fusion::nil>, boost::fusion::vector0<> >, boost::spirit::unused_type, boost::spirit::qi::simple_trace>; R = bool; T0 = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >&; T1 = const __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >&; T2 = boost::spirit::context<boost::fusion::cons<FactoryReturnType&, boost::fusion::nil>, boost::fusion::vector0<> >&; T3 = const boost::spirit::unused_type&; typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type = int]’
/usr/include/boost/function/function_template.hpp:1124:5:   required from ‘typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, boost::function<R(T0, T1, T2, T3)>&>::type boost::function<R(T0, T1, T2, T3)>::operator=(Functor) [with Functor = boost::spirit::qi::debug_handler<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, boost::spirit::context<boost::fusion::cons<FactoryReturnType&, boost::fusion::nil>, boost::fusion::vector0<> >, boost::spirit::unused_type, boost::spirit::qi::simple_trace>; R = bool; T0 = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >&; T1 = const __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >&; T2 = boost::spirit::context<boost::fusion::cons<FactoryReturnType&, boost::fusion::nil>, boost::fusion::vector0<> >&; T3 = const boost::spirit::unused_type&; typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, boost::function<R(T0, T1, T2, T3)>&>::type = boost::function<bool(__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >&, const __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >&, boost::spirit::context<boost::fusion::cons<FactoryReturnType&, boost::fusion::nil>, boost::fusion::vector0<> >&, const boost::spirit::unused_type&)>&]’
/usr/include/boost/spirit/home/qi/nonterminal/debug_handler.hpp:122:13:   required from ‘void boost::spirit::qi::debug(boost::spirit::qi::rule<Iterator, T1, T2, T3, T4>&) [with Iterator = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >; T1 = FactoryReturnType(); T2 = boost::spirit::unused_type; T3 = boost::spirit::unused_type; T4 = boost::spirit::unused_type]’
../src/AbnfReader.hpp:350:14:   required from ‘AbnfRules<Iterator>::AbnfRules() [with Iterator = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >]’
../src/AbnfReader.cpp:27:12:   required from here
/usr/include/boost/proto/operators.hpp:295:9: error: no type named ‘type’ in ‘struct boost::proto::detail::enable_binary<boost::proto::domainns_::deduce_domain, boost::proto::detail::not_a_grammar, boost::mpl::or_<boost::proto::is_extension<std::basic_ostream<char> >, boost::proto::is_extension<const boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, std::basic_string<char>()> > >, mpl_::bool_<false>, mpl_::bool_<false>, mpl_::bool_<false> >, boost::proto::tagns_::tag::shift_left, std::basic_ostream<char>&, const boost::spirit::qi::reference<const boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, std::basic_string<char>()> >&>’
make: *** [src/AbnfReader.o] Error 1

Answer 1

嗯，这很尴尬。在尝试编写像sehe建议的SSCCE时，我发现我的方法实际上一直在工作。我在试图解决这个问题时遇到了很多麻烦......：C

以下是我尝试做的一个工作示例。虽然它有效但行为仍然有点奇怪，这就是我认为它不能以这种方式工作的原因。

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

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

typedef qi::rule<std::string::const_iterator, std::string()> parserRule;


namespace std
{
std::ostream& operator<<(std::ostream& stream, const parserRule& val);
}
std::ostream& std::operator<<(std::ostream& stream, const parserRule& val)
{
    stream << "RULE( " << val.name();
    stream << " )";
    return stream;
}

class Factory
{
public:
    Factory(){}
    parserRule createParser(std::string str)
    {
        parserRule r;
        r = qi::char_(str);
        r.name("FactoryRule");
        std::cout << r.name() << " now parses >" + str + "<" << std::end;
        return r;
    }
};

template <typename Iterator>
struct TestGrammar : qi::grammar<Iterator, parserRule()>
{

    TestGrammar() : TestGrammar::base_type(start, "Test grammar")
    {
        start = stringRule.alias();
        stringRule =    (
                ascii::char_("'") >>
                *(ascii::char_ - ascii::char_("'"))[qi::_a += qi::_1] >>
                ascii::char_("'")
        )[qi::_val = px::bind(&Factory::createParser, &factory, qi::_a)];

        start.name("Start");
        stringRule.name("StringRule");

        qi::debug(start);       // shows "RULE( unnamed-rule )"
        qi::debug(stringRule);  // shows "RULE( unnamed-rule )"
    }

    qi::rule<Iterator, parserRule() > start;
    qi::rule<Iterator, parserRule(), qi::locals<std::string> > stringRule;
    Factory factory;
};

int main()
{
    typedef std::string::const_iterator iterator_type;
    typedef TestGrammar<iterator_type> TGrammar;


    TGrammar test_parser;

    std::string test = "parse THIS!";
    std::string input = "'"+test+"'";
    parserRule result;

    std::string::const_iterator iter = input.begin();
    std::string::const_iterator end = input.end();

    bool r = parse(iter, end, test_parser, result);

    if (r && iter == end)
    {
        std::cout << "-------------------------\n";
        std::cout << "1st Parsing succeeded\n";
        std::cout << "-------------------------\n";
    }
    else
    {
        std::string rest(iter, end);
        std::cout << "-------------------------\n";
        std::cout << "1st Parsing failed\n";
        std::cout << "stopped at: \"" << rest << "\"\n";
        std::cout << "-------------------------\n";
    }

    iterator_type first(test.begin()), last(test.end());

    qi::debug(result); //shows correct rule name
    r = qi::phrase_parse(first, last, result, boost::spirit::ascii::space);

    if (r && iter == end)
    {
        std::cout << "-------------------------\n";
        std::cout << "2nd Parsing succeeded\n";
        std::cout << "-------------------------\n";
    }
    else
    {
        std::string rest(first, last);
        std::cout << "-------------------------\n";
        std::cout << "2nd Parsing failed\n";
        std::cout << "stopped at: \"" << rest << "\"\n";
        std::cout << "-------------------------\n";
    }
}

这是输出：

FactoryRule now parses >parse THIS!<
<Start>
  <try>'parse THIS!'</try>
  <StringRule>
    <try>'parse THIS!'</try>
    <success></success>
    <attributes>[[RULE( unnamed-rule )]]</attributes><locals>(parse THIS!)</locals>
  </StringRule>
  <success></success>
  <attributes>[[RULE( unnamed-rule )]]</attributes>
</Start>
-------------------------
1st Parsing succeeded
-------------------------
<FactoryRule>
  <try>parse THIS!</try>
  <success>arse THIS!</success>
  <attributes>[[p]]</attributes>
</FactoryRule>
-------------------------
2nd Parsing succeeded
-------------------------

如您所见，调试规则start和stringRule将始终显示＆＃34; RULE（未命名规则）＆＃34;作为属性。这使我相信，在分配=结果时，由于使用了px::bind - 运算符，已分配的规则名称已丢失。由于调试result规则显示正确的名称，我假设＆＃34;未命名规则＆＃34;输出只是没有显示正确的FINAL合成属性，而是显示当前的＆＃34;空＆＃34;之一。

在我看到＆＃34;未命名的规则＆＃34;时，我会立刻感到恐慌。并花费很多天试图解决这个问题，甚至在这里询问，而不是通过调试result规则来实际测试整个事情。

感谢您无论如何都想帮助我。我希望这至少对其他人有用。

Answer 2

这里有两个问题，仅仅是经验，没有进一步的代码：

单元素适应结构构成问题，请参阅：[link coming]
调试信息需要专门调试打印特征（可以追溯到ostream流式传输）。显然，qi::rule尚未做到这一点。所以，要么添加它。

也许，也许你可以让包含结构iostream能够避免它（但我担心融合适应可能会优先考虑。这是一次尝试）

Q值。是的，你是对的。我必须在运行时动态编写语法。为了确保这是可能的，我已经编写了一堆按预期工作的测试片段。

非常生硬：精神不是那种工具。 Spirit是一种工具，可以从“praser表达式”生成静态编译的语法，这些表达式是表达式模板。整个目的是成为编译时并使用静态多态与完全优化。我建议可能创建一组运行时 - 多态解析器组件（你可以反过来，使用Spirit实现:)）并用它们组成你的动态语法。

一种可能的中间立场是使用qi::lazy和一组预定义的不可变“原子”规则（因此不是动态组合），并通过引用使用这些“原子”规则组合你的解析器。 / p>
基本上，只要您不尝试动态撰写表达式模板（而是现成的类型擦除非终端），您应该没事。

如果您需要更多，您很快就会进入UB-land。有些时候你可以使用boost::proto::deep_copy来解决问题，但是有一些限制。

boost :: spirit：qi ::包含qi :: rule的规则或结构作为解析结果

2 个答案: