X3，什么是attr_gen? [英] X3, what is attr_gen?
问题描述
我最终会遇到很多这些移动错误，并且除了与我解析字符串的方式有关之外，我不太确定为什么.删除所有与虚拟"有关的内容，错误会再次出现.
I end up getting these move errors a lot and am not quite sure why other than having something to do with the way I'm parsing strings. Remove everything having to do with 'dummy' and the errors come back.
有人提到使用attr_gen(无法在文档中找到它)，这样做，我可以克服这些"traits :: move_to"编译错误，但是解析器仍然失败.我已经标记了为使它可以编译而添加的行，但是认为不需要用< ---".
Someone mentioned using attr_gen (couldn't find this in the docs) and by doing so, I can get past these "traits::move_to" compile errors, but the parser still fails. I've marked the lines that I've added to get it to compile, but don't think are necessary with "<---".
#define BOOST_SPIRIT_X3_DEBUG
#include <complex>
#include <iostream>
#include <string>
#include <vector>
#include <boost/spirit/home/x3.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/include/io.hpp>
namespace client {
namespace ast {
struct number {
int num1;
int num2;
};
struct comment {
std::string text;
bool dummy; // <---
};
struct input {
std::vector<comment> comments;
std::vector<number> numbers;
};
}
}
BOOST_FUSION_ADAPT_STRUCT(client::ast::comment, text, dummy) // <---
BOOST_FUSION_ADAPT_STRUCT(client::ast::number, num1, num2)
BOOST_FUSION_ADAPT_STRUCT(client::ast::input, comments, numbers)
namespace client {
namespace parser {
namespace x3 = boost::spirit::x3;
namespace ascii = boost::spirit::x3::ascii;
using namespace x3;
x3::attr_gen dummy; // <---
auto const comment = char_ % ' ' >> dummy(false); // <---
//auto const comment = lexeme[+graph] >> dummy(false);
auto const number = int_ >> int_;
auto lines = [](auto p) { return *(p >> eol); };
auto const input = skip(blank) [
lines(comment) >>
lines(number)
];
}
}
int main()
{
namespace x3 = boost::spirit::x3;
using boost::spirit::x3::ascii::blank;
using x3::char_;
std::string const iss(R"(this is a test
1 2)");
auto iter = iss.begin(), eof = iss.end();
client::ast::input types;
bool ok = parse(iter, eof, client::parser::input, types);
if (iter != eof) {
std::cout << "Remaining unparsed: '" << std::string(iter, eof) << "'\n";
}
std::cout << "Parsed: " << (100.0 * std::distance(iss.begin(), iter) / iss.size()) << "%\n";
std::cout << "ok = " << ok << std::endl;
for (auto& item : types.comments) { std::cout << boost::fusion::as_deque(item) << "\n"; }
for (auto& item : types.numbers) { std::cout << boost::fusion::as_deque(item) << "\n"; }
}
推荐答案
x3::attr() is perfectly well documented (the generator type behind it is an implementation detail, much like you'd use x3::int_, not x3::int_gen).
您需要它的事实已经得到回答.关键是具有单元素融合序列.
The fact that you need it has been answered before. The key is having single-element fusion sequences.
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