提升精神 x3 变体和 std::pair

Question

我尝试运行一些简单的解析器来解析 [1, 11, 3, 6-4]。基本上，带有范围表示法的整数列表。

我想将所有内容都放入 AST 中，而不需要语义操作。所以我使用 x3::variant。我的代码“似乎”与表达式示例非常相似。但是，它不能在 g++ 6.2 下编译。它确实可以用 clang++ 6.0 编译，但产生错误的结果。

增强版本是 1.63。 看来我有一些“移动”或初始化问题。

#include <iostream>
#include <list>
#include <vector>
#include <utility> 

#include <boost/spirit/home/x3.hpp>
#include <boost/spirit/home/x3/support/ast/variant.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/adapted/std_pair.hpp>
#include <boost/fusion/include/io.hpp>

namespace ns
{
  namespace ast
  {
    namespace x3 = boost::spirit::x3;

    // forward definition
    class uintObj;
    struct varVec;

    // define type
    using uintPair_t = std::pair<unsigned int, unsigned int>;
    using uintVec_t = std::vector<uintObj>;

    // general token value:
    class uintObj : public x3::variant <
      unsigned int,
      uintPair_t
      >
    {
     public:
      using base_type::base_type;
      using base_type::operator=;
    };

    struct varVec
    {
      uintVec_t valVector;
    };
  }
}

BOOST_FUSION_ADAPT_STRUCT(
  ns::ast::varVec,
  valVector
  )

namespace ns
{
  namespace parser
  {
    // namespace x3 = boost::spirit::x3;
    // using namespace x3;
    using namespace boost::spirit::x3;

    // definition of the range pair:
    rule<class uintPair, ast::uintPair_t> const uintPair = "uintPair";

    auto const uintPair_def =
      uint_
      >> '-'
      >> uint_
      ;

    rule<class uintObj, ast::uintObj> const uintObj = "uintObj";

    auto const uintObj_def =
      uint_
      | uintPair
      ;

    // define rule definition : rule<ID, attrib>
    // more terse definition :
    // struct varVec_class;
    // using varVec_rule_t = x3::rule<varVec_class, ast::varVec>;
    // varVec_rule_t const varVec = "varVec";
    // varVec is the rule, "varVec" is the string name of the rule.
    rule<class varVec, ast::varVec> const varVec = "varVec";

    auto const varVec_def =
      '['
      >> uintObj % ','
      >> ']'
      ;

    BOOST_SPIRIT_DEFINE(
      varVec,
      uintObj,
      uintPair
      );
  }
}

int main()
{
  std::string input ("[1, 11, 3, 6-4]\n");
  std::string::const_iterator begin = input.begin();
  std::string::const_iterator end = input.end();

  ns::ast::varVec result;                 // ast tree
  using ns::parser::varVec;               // grammar
  using boost::spirit::x3::ascii::space;

  bool success = phrase_parse(begin, end, varVec, space, result);

  if (success && begin == end)
    std::cout << "good" << std::endl;
  else
    std::cout << "bad" << std::endl;

  return 0;
}

Answer 1

交换uintObj_def的替代顺序

auto const uintObj_def =
    uintPair
  | uint_
  ;

您现在拥有的公式将始终与uint_ 匹配，因为uintPair 以有效的uint_ 开头。

Answer 2

mjcaisse 的回答指出了我认为您遇到的主要问题。有一些缺失的部分，所以我决定制作一个显示解析结果的简化版本：

Live On Wandbox

#include <iostream>
#include <iomanip>

//#include <boost/fusion/adapted.hpp>
//#include <boost/fusion/include/io.hpp>
#include <boost/spirit/home/x3.hpp>
#include <boost/spirit/home/x3/support/ast/variant.hpp>

namespace x3 = boost::spirit::x3;

namespace ns { namespace ast {

    // forward definition
    struct uintObj;
    //struct varVec;

    // define type
    using uintPair_t = std::pair<unsigned int, unsigned int>;
    using uintVec_t = std::vector<uintObj>;

    // general token value:
    struct uintObj : x3::variant<unsigned int, uintPair_t> {
        using base_type::base_type;
        using base_type::operator=;

        friend std::ostream& operator<<(std::ostream& os, uintObj const& This) {
            struct {
                std::ostream& os;
                void operator()(unsigned int v) const { os << v; }
                void operator()(uintPair_t v) const { os << v.first << "-" << v.second; }
            } vis { os };
            boost::apply_visitor(vis, This);
            return os;
        }
    };

    using varVec = uintVec_t;
} }

namespace ns { namespace parser {
    using namespace boost::spirit::x3;

    template <typename T> auto as = [](auto p) { return rule<struct _, T> {} = p; };

    auto const uintPair = as<ast::uintPair_t> ( uint_ >> '-' >> uint_       );
    auto const uintObj  = as<ast::uintObj>    ( uintPair | uint_            );
    auto const varVec   = as<ast::varVec>     ( '[' >> uintObj % ',' >> ']' );
} }

int main() {
    using namespace ns;
    std::string const input("[1, 11, 3, 6-4]\n");
    auto begin = input.begin(), end = input.end();

    ast::varVec result; // ast tree
    bool success = phrase_parse(begin, end, parser::varVec, x3::ascii::space, result);

    if (success) {
        std::cout << "good\n";
        for (auto& r : result) 
            std::cout << r << "\n";
    }
    else
        std::cout << "bad\n";

    if (begin != end)
        std::cout << "Remaining unparsed: " << std::quoted(std::string(begin, end)) << std::endl;
}

打印

good
1
11
3
6-4