从Boost.Spirit语法属性：从错误的std：升压::变种矢量 [英] Attributes from Boost.Spirit grammar: error from std:vector of boost::variant
问题描述
我有一个工作解析器阅读棋盘游戏职位描述（国际汇票，官方语法）
I got a working parser for reading position descriptions for a board game (international draughts, official grammar):
#include <boost/spirit/home/x3.hpp>
#include <iostream>
namespace x3 = boost::spirit::x3;
auto const colon = x3::lit(':');
auto const comma = x3::lit(',');
auto const dash = x3::lit('-');
auto const dot = x3::lit('.');
auto const king = x3::char_('K');
auto const color = x3::char_("BW");
auto const num_sq = x3::int_;
auto const num_pc = -king >> num_sq; // Kxx means king on square xx, xx a man on that square
auto const num_rng = num_pc >> dash >> num_sq; // xx-yy means range of squares xx through yy (inclusive)
auto const num_seq = (num_rng | num_pc) % comma; // <--- attribute should be std::vector<boost::variant>
auto const ccn = colon >> color >> -num_seq;
auto const num_not = x3::repeat(2)[ccn]; // need to specify both white and black pieces
auto const fen = color >> num_not >> -dot;
<大骨节病> 住在Coliru
现在我想提取合成的属性值，所以我也围绕Boost.Fusion等样板舞蹈，
Now I want to extract the values from the synthesized attributes, so I did the boilerplate dance around Boost.Fusion etc.,
namespace ast {
struct num_pc { boost::optional<char> k; int sq; };
struct num_rng { boost::optional<char> k; int first, last; };
using rng_or_pc = boost::variant<num_rng, num_pc>;
struct num_seq { std::vector<rng_or_pc> sqrs; };
struct ccn { char c; boost::optional<num_seq> seq; };
struct num_not { std::vector<ccn> n; };
struct fen { char c; num_not n; };
} // namespace ast
BOOST_FUSION_ADAPT_STRUCT(ast::num_pc, (boost::optional<char>, k), (int, sq))
BOOST_FUSION_ADAPT_STRUCT(ast::num_rng, (boost::optional<char>, k), (int, first), (int, last))
BOOST_FUSION_ADAPT_STRUCT(ast::num_seq, (std::vector<ast::rng_or_pc>, sqrs))
BOOST_FUSION_ADAPT_STRUCT(ast::ccn, (char, c), (boost::optional<ast::num_seq>, seq))
BOOST_FUSION_ADAPT_STRUCT(ast::num_not, (std::vector<ast::ccn>, n))
BOOST_FUSION_ADAPT_STRUCT(ast::fen, (char, c), (ast::num_not, n))
x3::rule<class num_pc_class, ast::num_pc > num_pc = "num_pc";
x3::rule<class num_rng_class, ast::num_rng> num_rng = "num_rng";
x3::rule<class num_seq_class, ast::num_seq> num_seq = "num_seq";
x3::rule<class ccn_class, ast::ccn > ccn = "ccn";
x3::rule<class num_not_class, ast::num_not> num_not = "num_not";
x3::rule<class fen_class, ast::fen > fen = "fen";
auto const colon = x3::lit(':');
auto const comma = x3::lit(',');
auto const dash = x3::lit('-');
auto const dot = x3::lit('.');
auto const king = x3::char_('K');
auto const color = x3::char_("BW");
auto const num_sq = x3::int_;
auto const num_pc_def = -king >> num_sq;
auto const num_rng_def = num_pc >> dash >> num_sq;
auto const num_seq_def = (num_rng | num_pc) % comma;
auto const ccn_def = colon >> color >> -num_seq;
auto const num_not_def = x3::repeat(2)[ccn];
auto const fen_def = color >> num_not >> -dot;
BOOST_SPIRIT_DEFINE(num_pc, num_rng, num_seq, ccn, num_not, fen)
<大骨节病> 住在Coliru
不过，我然后得到一个错误，指出
However, I then get an error saying that
错误：static_assert失败属性不具有预期
大小。
error: static_assert failed "Attribute does not have the expected size."
和几页下来：
^的main.cpp：16：8：注意：候选构造函数（隐式转移构造函数）不可行的：没有已知的转换
的std ::矢量＆lt;提高::变体LT; AST :: num_rng，AST :: num_pc＆gt;中来
的std ::分配器＆LT;提高::变体LT; AST :: num_rng，AST :: num_pc＆GT; ＆GT; ＆GT;
AST :: num_seq'的第一个参数结构num_seq {
的std ::矢量＆lt;＆rng_or_pc GT; sqrs; };
^ main.cpp:16:8: note: candidate constructor (the implicit move constructor) not viable: no known conversion from '
std::vector<boost::variant<ast::num_rng, ast::num_pc>, std::allocator<boost::variant<ast::num_rng, ast::num_pc> > >' to 'ast::num_seq' for 1st argument struct num_seq {std::vector<rng_or_pc>sqrs; };
^的main.cpp：16：8：注意：候选构造函数（隐式拷贝构造函数）不可行的：没有已知的转换
的std ::矢量＆lt;提高::变体LT; AST :: num_rng，AST :: num_pc＆gt;中来
的std ::分配器＆LT;提高::变体LT; AST :: num_rng，AST :: num_pc＆GT; ＆GT; ＆GT;
常量AST :: num_seq'的第一个参数结构num_seq {
的std ::矢量＆lt;＆rng_or_pc GT; sqrs; };
^ main.cpp:16:8: note: candidate constructor (the implicit copy constructor) not viable: no known conversion from
'std::vector<boost::variant<ast::num_rng, ast::num_pc>,
std::allocator<boost::variant<ast::num_rng, ast::num_pc> > >' to
'const ast::num_seq' for 1st argument struct num_seq {
std::vector<rng_or_pc> sqrs; };
问：其中是来自此错误，以及如何解决它？显然，我的 num_seq 规则的综合属性不等于的std ::矢量＆lt;增强::变种＆GT;＆GT; 。我怎样才能解决这个？
Question: where is this error coming from, and how to resolve it? Apparently the synthesized attribute of my num_seq rule is not equal to std::vector<boost::variant>>. How can I correct this?
推荐答案
我花了一些时间去理解语法。
I've spent some time trying to understand the grammar.
的我强烈建议可读的标识符。这是很难理解这是怎么回事，而我有很强的IM pression它实际上是一个非常简单的语法的
我建议如下所示的简化版本。
I suggest a simplification version shown below.
- 因为你的语法并不使用递归有该规则没有真正的需要和标签解析器类型。
- 也可以使用一个命名空间解析器文物。
- 考虑封装采用了船长，而不是让来电者决定的（
X3 ::跳过[]） -
添加几个助手能够打印的AST进行验证：
- Because your grammar doesn't use recursion there's no real need for the rule and tagged parser types.
- Also use a namespace for the parser artefacts.
- Consider encapsulation the use of a skipper instead of letting the caller decide (
x3::skip[]) Add a few helpers to be able to print the AST for verification:
template <typename T> std::ostream& operator<<(std::ostream& os, std::vector<T> const& v) {
os << "{"; for (auto& el : v) os << el << " "; return os << "}";
}
std::ostream& operator<<(std::ostream& os, num_pc const& p) { if (p.k) os << p.k; return os << p.sq; }
std::ostream& operator<<(std::ostream& os, num_rng const& r) { return os << r.pc << "-" << r.last; }
std::ostream& operator<<(std::ostream& os, ccn const& o) { return os << o.c << " " << o.seq; }
std::ostream& operator<<(std::ostream& os, num_not const& nn) { return os << nn.n; }
我会避免缠绕其他矢量不必要太：
I'd avoid wrapping the other vector unnecessarily too:
using num_not = std::vector<ccn>;
使用现代ADAPT宏（如你正在使用C ++ 14的定义）：
Use the modern ADAPT macros (as you're using C++14 by definition):
BOOST_FUSION_ADAPT_STRUCT(ast::num_pc, k, sq)
BOOST_FUSION_ADAPT_STRUCT(ast::num_rng, pc, last)
BOOST_FUSION_ADAPT_STRUCT(ast::ccn, c, seq)
BOOST_FUSION_ADAPT_STRUCT(ast::fen, c, n)
-
-
<大骨节病> 住在Coliru
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/include/as_vector.hpp>
#include <boost/fusion/include/io.hpp>
#include <boost/optional/optional_io.hpp>
#include <boost/optional.hpp>
#include <boost/spirit/home/x3.hpp>
#include <boost/variant.hpp>
#include <iostream>
#include <vector>
namespace ast {
struct num_pc {
boost::optional<char> k;
int sq;
};
struct num_rng {
num_pc pc;
int last;
};
using rng_or_pc = boost::variant<num_rng, num_pc>;
using num_seq = std::vector<rng_or_pc>;
struct ccn {
char c;
boost::optional<num_seq> seq;
};
using num_not = std::vector<ccn>;
struct fen {
char c;
num_not n;
};
template <typename T> std::ostream& operator<<(std::ostream& os, std::vector<T> const& v) {
os << "{"; for (auto& el : v) os << el << " "; return os << "}";
}
std::ostream& operator<<(std::ostream& os, num_pc const& p) { if (p.k) os << p.k; return os << p.sq; }
std::ostream& operator<<(std::ostream& os, num_rng const& r) { return os << r.pc << "-" << r.last; }
std::ostream& operator<<(std::ostream& os, ccn const& o) { return os << o.c << " " << o.seq; }
}
BOOST_FUSION_ADAPT_STRUCT(ast::num_pc, k, sq)
BOOST_FUSION_ADAPT_STRUCT(ast::num_rng, pc, last)
BOOST_FUSION_ADAPT_STRUCT(ast::ccn, c, seq)
BOOST_FUSION_ADAPT_STRUCT(ast::fen, c, n)
namespace FEN {
namespace x3 = boost::spirit::x3;
namespace grammar
{
using namespace x3;
template<typename T>
auto as = [](auto p) { return rule<struct _, T>{} = as_parser(p); };
uint_type const number {};
auto const color = char_("BW");
auto const num_pc = as<ast::num_pc> ( -char_('K') >> number );
auto const num_rng = as<ast::num_rng> ( num_pc >> '-' >> number );
auto const num_seq = as<ast::num_seq> ( (num_rng | num_pc) % ',' );
auto const ccn = as<ast::ccn> ( ':' >> color >> -num_seq );
auto const num_not = as<ast::num_not> ( repeat(2)[ccn] );
auto const fen = as<ast::fen> ( color >> num_not >> -lit('.') );
}
using grammar::fen;
}
int main() {
for (std::string const t : {
"B:W18,24,27,28,K10,K15:B12,16,20,K22,K25,K29",
"B:W18,19,21,23,24,26,29,30,31,32:B1,2,3,4,6,7,9,10,11,12",
"W:B1-20:W31-50", // initial position
"W:B:W", // empty board
"W:B1:W", // only black pieces
"W:B:W50" // only white pieces
}) {
auto b = t.begin(), e = t.end();
ast::fen data;
bool ok = phrase_parse(b, e, FEN::fen, FEN::x3::space, data);
std::cout << t << "\n";
if (ok) {
std::cout << "Parsed: " << boost::fusion::as_vector(data) << "\n";
} else {
std::cout << "Parse failed:\n";
std::cout << "\t on input: " << t << "\n";
}
if (b != e)
std::cout << "\t Remaining unparsed: '" << std::string(b, e) << '\n';
}
}
打印：
B:W18,24,27,28,K10,K15:B12,16,20,K22,K25,K29
Parsed: (B {W {18 24 27 28 K10 K15 } B {12 16 20 K22 K25 K29 } })
B:W18,19,21,23,24,26,29,30,31,32:B1,2,3,4,6,7,9,10,11,12
Parsed: (B {W {18 19 21 23 24 26 29 30 31 32 } B {1 2 3 4 6 7 9 10 11 12 } })
W:B1-20:W31-50
Parsed: (W {B {1-20 } W {31-50 } })
W:B:W
Parsed: (W {B -- W -- })
W:B1:W
Parsed: (W {B {1 } W -- })
W:B:W50
Parsed: (W {B -- W {50 } })
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