boost::spirit 算术公式解析器编译失败

Question

我正在尝试为填充抽象语法树的算术表达式编写精神解析器。如果我不尝试填充 AST，解析器会编译，但在当前版本中会失败（有一个 24K 错误）。我在 Ubuntu 14.4.

上使用带有 -std=c++11 和运行的 clang++ 3.5.0

#include <string>
#include <vector>
#include <utility>

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

#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/adapted.hpp>
#include <boost/fusion/include/adapted.hpp>

#include <boost/variant/variant.hpp>
#include <boost/variant/recursive_wrapper.hpp>

using std::string;
using std::vector;
using std::pair;

using boost::spirit::qi::grammar;
using boost::spirit::qi::space_type;
using boost::spirit::qi::rule;

struct Term; // forward dec
typedef boost::recursive_wrapper<Term> RWTerm;
typedef pair<char, RWTerm> OpAndRWTerm;
typedef pair<RWTerm, vector<OpAndRWTerm> > Expr;
typedef boost::variant<Expr, double> Factor;
typedef pair<char, Factor> OpAndFactor;
struct Term : public pair<Factor, vector<OpAndFactor> >{};

template<typename It>
struct formula_parser : grammar<It, Expr(), space_type> {
  formula_parser() : formula_parser::base_type(expr_rule) {
    using boost::spirit::qi::double_;
    using boost::spirit::ascii::char_;

    factor_rule %= double_ | parenthesis_rule;
    parenthesis_rule %= '(' >> expr_rule >> ')';
    op_and_factor_rule %= char_("/*") >> factor_rule;
    term_rule %= factor_rule >> *op_and_factor_rule;
    op_and_term_rule %= char_("+-") >> term_rule;
    expr_rule %= term_rule >> *op_and_term_rule;
  }
  rule<It, OpAndRWTerm(), space_type> op_and_term_rule;
  rule<It, Expr(), space_type> expr_rule;
  rule<It, OpAndFactor(), space_type> op_and_factor_rule;
  rule<It, RWTerm(), space_type> term_rule;
  rule<It, Expr(), space_type> parenthesis_rule;
  rule<It, Factor(), space_type> factor_rule;
};

int main() {
  formula_parser<string::const_iterator> grammar;
}

我从错误消息中了解到，融合混淆了规则 term_rule 中的类型因子和 RWTerm。

我做错了什么？

Answer 1

如果我改变两件事，它会为我编译：

由于 Term 继承自 std::pair，Term 是 new 类型。因此，您需要将 BOOST_FUSION_ADAPT_STRUCT 应用到 Term，无论是否已经在 <boost/fusion/adapted/std_pair.hpp>:
中对 std::pair 应用
```
BOOST_FUSION_ADAPT_STRUCT(
    Term,
    (Factor, first)
    (std::vector<OpAndFactor>, second)
)
```
或者，您可以使 Term 成为具有两个成员的独立结构，然后在其上应用 BOOST_FUSION_ADAPT_STRUCT：
```
struct Term { Factor f; std::vector<OpAndFactor>  o;};

BOOST_FUSION_ADAPT_STRUCT(
    Term,
    (Factor, f)
    (std::vector<OpAndFactor>, o)
)
```
顺便说一句：你必须在这里完全限定 std::vector，因为下面的 will not compile:
```
using std::vector;
BOOST_FUSION_ADAPT_STRUCT(
    Term,
    (Factor, f)
    (vector<OpAndFactor>, o)
)
```
在声明 term_rule 时使用 Term 而不是 RWTerm：
```
rule<It, Term(), space_type> term_rule;
```

完整代码：

#include <string>
#include <vector>
#include <utility>

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

#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/adapted.hpp>
#include <boost/fusion/include/adapted.hpp>

#include <boost/variant/variant.hpp>
#include <boost/variant/recursive_wrapper.hpp>

using boost::spirit::qi::grammar;
using boost::spirit::qi::space_type;
using boost::spirit::qi::rule;

struct Term; // forward dec
typedef boost::recursive_wrapper<Term> RWTerm;
typedef std::pair<char, RWTerm> OpAndRWTerm;
typedef std::pair<RWTerm, std::vector<OpAndRWTerm> > Expr;
typedef boost::variant<Expr, double> Factor;
typedef std::pair<char, Factor> OpAndFactor;
struct Term : public std::pair<Factor, std::vector<OpAndFactor> >{};

BOOST_FUSION_ADAPT_STRUCT(
    Term,
    (Factor, first)
    (std::vector<OpAndFactor>, second)
)


template<typename It>
struct formula_parser : grammar<It, Expr(), space_type> {
  formula_parser() : formula_parser::base_type(expr_rule) {
    using boost::spirit::qi::double_;
    using boost::spirit::ascii::char_;

    factor_rule %= double_ | parenthesis_rule;
    parenthesis_rule %= '(' >> expr_rule >> ')';
    op_and_factor_rule %= char_("/*") >> factor_rule;
    term_rule %= factor_rule >> *op_and_factor_rule;
    op_and_term_rule %= char_("+-") >> term_rule;
    expr_rule %= term_rule >> *op_and_term_rule;
  }
  rule<It, OpAndRWTerm(), space_type> op_and_term_rule;
  rule<It, Expr(), space_type> expr_rule;
  rule<It, OpAndFactor(), space_type> op_and_factor_rule;
  rule<It, Term(), space_type> term_rule;
  rule<It, Expr(), space_type> parenthesis_rule;
  rule<It, Factor(), space_type> factor_rule;
};

int main() {
  formula_parser<std::string::const_iterator> grammar;
}

live example

boost::spirit 算术公式解析器编译失败

boost::spirit arithmetic formulas parser fails to compile

c++

boost-fusion

boost-variant

boost-spirit-qi