如何在AST中使用Boost Spirit自动规则?

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问题描述

我扩展了sehe的示例，以在我要在另一条规则上使用它时显示该问题: http://liveworkspace.org/code/22lxL7 $ 17

I expanded sehe's example to show the problem when I want to use it on another rule: http://liveworkspace.org/code/22lxL7$17

我正在尝试提高Boost Spirit解析器的性能，并且看到自C ++ 11起，就可以使用这样的自动规则:

I'm trying to improve the performances of my Boost Spirit parser and I saw that since C++11, it was possible to use auto-rules like that:

auto comment = "/*" >> *(char_ - "*/") >> "*/";

(或使用BOOST_AUTO或BOOST_SPIRIT_AUTO).

(or with BOOST_AUTO or BOOST_SPIRIT_AUTO).

我有一个这样的规则声明者:

I have a rule declarer like that:

qi::rule<lexer::Iterator, ast::SimpleType()> simple_type;

并定义如下:

simple_type %=
        const_
    >>  lexer.identifier;

如果我用auto声明它，它将编译，但不能在其他规则中用作AST.

If I declare it with auto, it compiles, but it cannot be used as AST in other rules.

是否可以定义使用自动规则创建AST的规则?我也对在Boost Spirit中加快AST创建的其他方式感兴趣.

Is it possible to define rules creating AST with auto rules ?I'm also interested in other ways to speedup AST creation in Boost Spirit.

推荐答案

首先，我尝试了一个简单的示例，并使用简单的适应结构对我有用":

First of all, I tried a simple example and "it works for me" with a simple adapted struct:

struct fixed
{
    int integral;
    unsigned fractional;
};

BOOST_FUSION_ADAPT_STRUCT(fixed, (int, integral)(unsigned, fractional));

template <typename It, typename Skipper = qi::space_type>
    struct parser : qi::grammar<It, std::vector<fixed>(), Skipper>
{
    parser() : parser::base_type(start)
    {
        using namespace qi;

        BOOST_SPIRIT_AUTO(qi, fixed_rule, lexeme [ int_ >> -('.' >> uint_ | attr(0u)) ]);
        start = *fixed_rule;

        BOOST_SPIRIT_DEBUG_NODE(start);
    }

  private:
    qi::rule<It, std::vector<fixed>(), Skipper> start;
};

这很高兴地解析了输入: http://liveworkspace.org/code/22lxL7$1

This happily parses the inputs: http://liveworkspace.org/code/22lxL7$1

我想您可能是说要求属性兼容的地方，并且

I think you might mean where attribute compatibility is required, and

attr_cast (doc)
as< T(parse_expr) (doc)

应该能够帮上大忙.

有关attr_cast(以及一般的属性兼容性)的更多详细信息，请参见以下答案:

See this answer for more details on attr_cast (and attribute compatibility in general): String parser with boost variant recursive wrapper

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