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dridk/main.cpp

Last active May 7, 2019
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SQL parser with spirit X3 in C++
#include <boost/spirit.hpp>
#include <string>
#include <typeinfo>
namespace VQL
{
template <typename Iterator>
auto parse(Iterator begin, Iterator end, bool& success)
{
using namespace boost::spirit::x3;
using x3::lexeme;
using x3::alpha;
using x3::phrase_parse;
using x3::ascii::space;
using x3::_attr;
vector<std::string> select;
std::string from;
std::string where;
std::string region;
auto toSelect = [&](auto & ctx) {select = _attr(ctx);};
auto toFrom = [&](auto & ctx) {from = _attr(ctx);};
auto toWhere = [&](auto & ctx) {where = _attr(ctx);};
auto toRegion = [&](auto & ctx) {region = _attr(ctx);};
auto keywords = x3::lit("SELECT") |
x3::lit("FROM") |
x3::lit("WHERE") |
x3::lit("REGION");
auto word = *(x3::alnum - keywords);
auto cond = *(x3::char_ - keywords);
success = phrase_parse(begin, end,
"SELECT" >>
(word % ",")[toSelect] >>
("FROM" >> word[toFrom]) >>
-("WHERE" >> x3::lexeme[cond][toWhere]) >>
-("REGION" >> word[toRegion])
,
space
);
return std::make_tuple(select,from,where,region);
}
}
int main(int argc, char **argv)
{
std::string query = "SELECT chr, pos,chrom FROM variants WHERE chr=3 AND chr=4 REGION exonic";
bool success = false;
auto results = VQL::parse(query.begin(), query.end(), success);
if (success)
{
for (auto& field : std::get<0>(results))
std::cout<<"fields "<<field<<"\n";
std::cout<<"from "<< std::get<1>(results)<<std::endl;
std::cout<<"where "<< std::get<2>(results)<<std::endl;
std::cout<<"region "<< std::get<3>(results)<<std::endl;
std::cout<<std::flush;
}
}
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