c++ - boost::spirit: qi::rule 或包含 qi::rule 作为解析结果的结构

Question

我想做的是在运行时从 ABNF 语法文件创建一个解析器。我已经在 qi::grammar 中实现了所有 ABNF 规则，如下所示:

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中，根据读入的语法创建了一个新的qi::rule:

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(就像我通常预期的那样)，我将丢失在 ParserFactory 中分配的每个规则名称(如在 fromRule 中) .我想这是由 spirit 内部工作方式引起的(= 运算符总是创建一个新的未命名规则。并且 = 用于分配 px::bind 函数结果)

但是，如果我尝试将我的 qi::rule 包装到一个结构中以避免这个问题，我将无法再使用 spirit 调试来编译我的代码。这是我尝试过的:

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(在这里发帖太长了)。我已经搜索了几天试图解决这个问题，但没有任何运气。我希望我提到了足够的细节。

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。在尝试按照 sehe 的建议编写 SSCCE 时，我发现我的方法实际上一直有效。我在尝试解决这个问题时遇到了很多麻烦...:C

这是我尝试做的工作示例。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“RULE( unnamed-rule )”作为属性。这让我相信，由于在分配 px::bind 结果时使用了 = 运算符，分配的规则名称丢失了。由于调试 result 规则显示了正确的名称，我假设“未命名规则”输出根本没有显示正确的最终合成属性，而是显示当前的“空”属性。

当我看到“未命名规则”并花了很多天试图解决这个问题，甚至在没有通过调试 result 规则实际测试整个事情的情况下在这里询问时，我感到非常羞耻.

无论如何，谢谢你试图帮助我。我希望这至少对其他人有用。