精神x3如何添加一個向量的AST

Question

我想解析一個文件，並將數據複製到一個類對象內的向量。我採取了員工示例，並將其修改爲我正在嘗試執行的操作。正在解析的文件看起來像這樣（但多行）...

1 0.2 0.3 0.4 

我添加了一個向量爲結構的員工和我在phrase_parse線越來越斷言失敗。

static assertion failed: Attribute does not have the expected size. 
static_assert(
^ 

我有點認爲預期的大小與矢量有關。關於我哪裏出錯的想法？

namespace client { 
    namespace ast { 

    struct employee 
    { 
     int id; 
     std::vector<double> coords; 
    }; 

    using boost::fusion::operator<<; 
}} 

BOOST_FUSION_ADAPT_STRUCT(
    client::ast::employee, 
    (int, id) 
    (std::vector<double>, coords) 
) 

namespace client 
{ 
    namespace parser 
    { 
     namespace x3 = boost::spirit::x3; 
     namespace ascii = boost::spirit::x3::ascii; 

     using x3::int_; 
     using x3::double_; 

     x3::rule<class employee, ast::employee> const employee = "employee"; 
     auto const employee_def = 
      int_ >> double_ >> double_ >> double_; 
     BOOST_SPIRIT_DEFINE(employee) 
    } 
} 

int main() 
{ 
    using boost::spirit::x3::ascii::space; 
    using client::parser::employee; 

    string fil("test-file.in"); 

    mapped_file_source map(fil); 
    istringstream iss(map.data()); 
    map.close(); 

    client::ast::employee emp; 

    boost::spirit::istream_iterator iter(iss >> noskipws), eof; 

    phrase_parse(iter, eof, employee, space, emp); 
    // failure on above line 
} 

Answer 1

根據文檔，double_ >> double_ >> double_來合成融合的序列雙，雙，雙（所以fusion::tuple<double, double, double>或fusion::list<double, double, double>等）。

你想要一個載體，所以你需要一個重複的解析器（運營商）

• 重複指令將做repeat(3) [double_]
• Kleene星號（operator *）或加號（operator +）很有趣（但無界）
• 列表運算符（operator %）也無界但接受分隔符（例如double_ % ','

在這種情況下，我會走另一條路：用適當的AST的語法：

Live On Coliru

struct coord { 
    double x,y,z; 
}; 

struct employee 
{ 
    int id; 
    coord coords; 
}; 

適應他們比你使用老式的方法更簡單：

BOOST_FUSION_ADAPT_STRUCT(client::ast::coord, x, y, z) 
BOOST_FUSION_ADAPT_STRUCT(client::ast::employee, id, coords) 

解析器是一個乾淨

auto const coord_def = double_ >> double_ >> double_; 
auto const employee_def = int_ >> coord; 

完整的示例：

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#include <boost/spirit/home/x3.hpp> 
#include <boost/spirit/include/support_istream_iterator.hpp> 
#include <boost/fusion/adapted/struct.hpp> 
#include <iostream> 

namespace client { 
    namespace ast { 

    struct coord { 
     double x,y,z; 
    }; 

    struct employee 
    { 
     int id; 
     coord coords; 
    }; 

    using boost::fusion::operator<<; 
}} 

BOOST_FUSION_ADAPT_STRUCT(client::ast::coord, x, y, z) 
BOOST_FUSION_ADAPT_STRUCT(client::ast::employee, id, coords) 

namespace client 
{ 
    namespace parser 
    { 
     namespace x3 = boost::spirit::x3; 
     namespace ascii = boost::spirit::x3::ascii; 

     using x3::int_; 
     using x3::double_; 

     x3::rule<class employee, ast::coord> const coord = "coord"; 
     x3::rule<class employee, ast::employee> const employee = "employee"; 

     auto const coord_def = double_ >> double_ >> double_; 
     auto const employee_def = int_ >> coord; 

     BOOST_SPIRIT_DEFINE(employee, coord); 
    } 
} 

int main() 
{ 
    using boost::spirit::x3::ascii::space; 
    using client::parser::employee; 

    std::istringstream iss("1 0.2 0.3 0.4"); 

    client::ast::employee emp; 

    boost::spirit::istream_iterator iter(iss >> std::noskipws), eof; 

    bool ok = phrase_parse(iter, eof, employee, space, emp); 
    if (ok) 
     std::cout << "parsed: " 
      << emp.id  << " " 
      << emp.coords.x << " " 
      << emp.coords.y << " " 
      << emp.coords.z << "\n"; 
}