在我的boost :: spirit语法中,我有以下片段;
implicit_method_declaration = (-(qi::token(ABSTRACT)) >> ...)
– (qi :: token(ABSTRACT)的类型是boost :: optional< boost :: iterator_range< std :: string :: iterator>>但是我只是使用这个构造来检查是否抽象关键字,实际上是现在,也就是说,我宁愿 – (qi :: token(ABSTRACT)的类型为bool,值为boost :: optional< ...> operator bool()const.
我将如何实现这一目标？
解决方法
我想你正在寻找qi :: matches []：
implicit_method_declaration =
qi::matches[qi::token(ABSTRACT)] >> ...;
implicit_method_declaration =
(
qi::token(ABSTRACT) >> qi::attr(true)
| qi::attr(false)
) >> ...;
再次快速演示：http://coliru.stacked-crooked.com/a/ed8bbad53e8c1943
#include <boost/spirit/include/qi.hpp>
namespace qi = boost::spirit::qi;
template <typename It,typename Skipper = qi::space_type>
struct parser : qi::grammar<It,bool(),Skipper>
{
parser() : parser::base_type(implicit_method_declaration)
{
using namespace qi;
implicit_method_declaration = matches["abstract"];
BOOST_SPIRIT_DEBUG_NODES((implicit_method_declaration));
}
private:
qi::rule<It,Skipper> implicit_method_declaration;
};
bool doParse(const std::string& input)
{
typedef std::string::const_iterator It;
auto f(begin(input)),l(end(input));
parser<It,qi::space_type> p;
bool data;
try
{
bool ok = qi::phrase_parse(f,l,p,qi::space,data);
if (ok)
{
std::cout << "parse success\n";
std::cout << "data: " << data << "\n";
}
else std::cerr << "parse Failed: '" << std::string(f,l) << "'\n";
if (f!=l) std::cerr << "trailing unparsed: '" << std::string(f,l) << "'\n";
return ok;
} catch(const qi::expectation_failure<It>& e)
{
std::string frag(e.first,e.last);
std::cerr << e.what() << "'" << frag << "'\n";
}
return false;
}
int main()
{
doParse("abstract");
doParse("static final");
}
产量
parse success data: 1 parse success data: 0 trailing unparsed: 'static final'
