我正在尝试(但失败)使用Boost Spirit X3通过以下代码来解析map<int, variant<string, float>>
:
#include <boost/spirit/home/x3/support/ast/variant.hpp>
#include <boost/fusion/adapted/struct.hpp>
#include <boost/spirit/home/x3.hpp>
#include <iostream>
#include <map>
#include <variant>
#include <string>
using namespace std;
namespace x3 = boost::spirit::x3;
int main() {
auto variantRule = x3::rule<class VariantClass, x3::variant<std::string, float>>() = (*x3::alnum | x3::float_);
auto pairRule = x3::rule<class PairClass, pair<int, x3::variant<std::string, float>>>() = x3::int_ >> ":" >> variantRule;
auto mapRule = x3::rule<class MapClass, map<int, x3::variant<std::string, float>>>() = pairRule >> * ( "," >> pairRule );
string input = "1 : 1.0, 2 : hello, 3 : world";
map<int, x3::variant<std::string, float>> variantMap;
auto success = x3::phrase_parse(input.begin(), input.end(), mapRule, x3::space, variantMap);
return 0;
}
由于某种原因,我无法解析pair<int, variant<string, float>>
的地图。但是,我能够解析变体的向量,只有当我尝试解析变体的映射时,我的代码才会失败。值得一提的是,我还完成了X3教程。任何帮助将不胜感激。
编辑1
考虑到@liliscent的回答以及其他一些更改,我终于能够使它工作,这里是正确的代码:
#include <boost/spirit/home/x3/support/ast/variant.hpp>
#include <boost/fusion/adapted/std_pair.hpp>
#include <boost/spirit/home/x3.hpp>
#include <iostream>
#include <map>
#include <variant>
#include <string>
using namespace std;
namespace x3 = boost::spirit::x3;
int main() {
auto stringRule = x3::rule<class StringClass, string>() = x3::lexeme[x3::alpha >> *x3::alnum];
auto variantRule = x3::rule<class VariantClass, x3::variant<std::string, float>>() = (stringRule | x3::float_);
auto pairRule = x3::rule<class PairClass, pair<int, x3::variant<std::string, float>>>() = x3::int_ >> ':' >> variantRule;
auto mapRule = x3::rule<class MapClass, map<int, x3::variant<std::string, float>>>() = pairRule % ",";
string input = "1 : 1.0, 2 : hello, 3 : world";
map<int, x3::variant<std::string, float>> variantMap;
auto bg = input.begin(), ed = input.end();
auto success = x3::phrase_parse(bg, ed, mapRule, x3::space, variantMap) && bg == ed;
if (!success) cout<<"Parsing not succesfull";
return 0;
}
答案 0 :(得分:3)
如果您想让spirit
识别std::pair
和std::map
,则需要包括std::pair
的融合适配器:
#include <boost/fusion/adapted/std_pair.hpp>
这应该可以解决您的compilation problem。但是您的代码中还有其他问题,该规则(*x3::alnum | x3::float_);
不能满足您的要求,因为左侧部分可以直接匹配为空。您需要重新考虑如何定义此标识符。
此外,写pairRule % ","
比写pairRule >> * ( "," >> pairRule );
更好。
您应该将输入作为左值迭代器开始传递,因为这样它将在解析期间进行高级处理,以便您可以检查解析器是否提前终止。