我一直在尝试使用 Boost Spirit 解析字符串,如下所示:
integer_count int1 int2 int3 ... intN
其中 N 是 integer_count。例如,
5 1 2 3 4 5
代码如下:
#define BOOST_SPIRIT_USE_PHOENIX_V3
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <string>
namespace qi = boost::spirit::qi;
namespace spirit = boost::spirit;
namespace ascii = boost::spirit::ascii;
using boost::phoenix::ref;
template <typename Iterator>
struct x_grammar : public qi::grammar<Iterator, std::string(), ascii::space_type>
{
public:
x_grammar() : x_grammar::base_type(start_rule, "x_grammar")
{
using namespace qi;
int repeat_count = 0;
start_rule = int_[ref(repeat_count) = _1] > repeater > *char_;
std::cout << "repeat_count == " << repeat_count << std::endl;
repeater = repeat(repeat_count)[int_[std::cout << _1 << ".\n"]];
}
private:
qi::rule<Iterator, std::string(), ascii::space_type> start_rule;
qi::rule<Iterator, std::string(), ascii::space_type> repeater;
};
int main()
{
typedef std::string::const_iterator iter;
std::string storage("5 1 2 3 4 5 garbage");
iter it_begin(storage.begin());
iter it_end(storage.end());
std::string read_data;
using boost::spirit::ascii::space;
x_grammar<iter> g;
try {
bool r = qi::phrase_parse(it_begin, it_end, g, space, read_data);
if(r) {
std::cout << "Pass!\n";
} else {
std::cout << "Fail!\n";
}
} catch (const qi::expectation_failure<iter>& x) {
std::cout << "Fail!\n";
}
}
输出是:
repeat_count == 0
Pass!
意思就是
ref(repeat_count) = _1
从未被调用。那么有没有办法将整数运行时读入局部变量并使用该值进行进一步解析?