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[英]Can I use BOOST_FUSION_ADAPT_STRUCT with struct consisting of std::vector?
[英]BOOST_FUSION_ADAPT_STRUCT using a recursive struct with a std::vector<self_type> member
我正在嘗試為 spirit x3 解析器聲明遞歸 AST。 解析器語法正在運行,並且由於建議避免語義操作,我正在嘗試改編Rexpr 官方文檔示例。
在主文檔中,解析的結構可以用 map 表示,其中鍵是字符串,值是字符串或另一個 map。
在我的例子中,被解析的結構是一個簡單的 n-ary 樹,我希望我能用遞歸結構和forward_ast
解決問題:
#include <boost/spirit/home/x3.hpp>
#include <boost/spirit/home/x3/support/ast/variant.hpp>
#include <boost/fusion/adapted/struct/adapt_struct.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
namespace ast
{
struct node
{
std::string name;
double length;
std::vector<boost::spirit::x3::forward_ast<node>> children;
};
}
BOOST_FUSION_ADAPT_STRUCT(ast::node, name, length, children)
但是我沒有成功編譯 - boost fusion 告訴我
error: explicit specialization of undeclared template struct 'tag_of'
BOOST_FUSION_ADAPT_STRUCT(ast::node, name, length, children)
所以我想我也不明白:
我不確定我是否解決了這個問題,但這也許有幫助:
#include <boost/spirit/home/x3.hpp>
#include <boost/spirit/home/x3/support/ast/variant.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/include/io.hpp>
#include <iostream>
namespace ast {
using boost::spirit::x3::forward_ast;
struct node {
std::string name;
double length;
std::vector<forward_ast<node>> children;
};
} // namespace ast
BOOST_FUSION_ADAPT_STRUCT(ast::node, name, length, children)
namespace ast {
using boost::fusion::operator<<;
static inline std::ostream& operator<<(std::ostream& os, std::vector<forward_ast<node>> const& nn) {
os << "[";
auto sep = "";
for (auto& n : nn)
os << std::exchange(sep, ", ") << n.get();
return os << "]";
}
} // namespace ast
int main() {
ast::node n{
"demo",
42,
{
ast::node{"nested1", 43, {}},
ast::node{"nested4",
47,
{
ast::node{"nested2", 45, {}},
ast::node{"nested3", 46, {}},
}},
ast::node{"nested5", 48, {}},
},
};
std::cout << "No problem: " << n << "\n";
}
印刷
No problem: (demo 42 [(nested1 43 []), (nested4 47 [(nested2 45 []), (nested3 46 [])]), (nested5 48 [])])
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