精神 x3 如何将矢量添加到 AST

Question

我正在尝试解析一个文件并将数据复制到类对象中的向量中。我以员工为例，并将其修改为我正在尝试做的事情。正在解析的文件看起来像这样(但更多行(...

1 0.2 0.3 0.4

我已经为结构员工添加了一个向量，并且在phrase_parse行上遇到断言失败。

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

我有点认为预期的大小与矢量有关。关于我哪里出错的想法？

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

根据文档，double_ >> double_ >> double_合成了双精度、双精度、双精度(如此fusion::tuple<double, double, double>或fusion::list<double, double, double>等(的融合序列。

你想要一个向量，所以你需要一个重复解析器(运算符(

• 重复指令将执行repeat(3) [double_]
• 克莱恩星(operator *(或加号(operator +(很有趣(但无界(
• 列表运算符(operator %(也是无界的，但接受分隔符(例如double_ % ','

在这种情况下，我会走另一条路：为语法使用适当的 AST：

住在科里鲁

struct coord {
double x,y,z;
};
struct employee
{
int id;
coord coords;
};

调整它们比您使用的老式方法更简单：

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

解析器是一个干净的

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

完整演示：

住在科里鲁

#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";
}