Compile error due boost spirit placeholder limit not more than 10

问题

I'm getting a

"qi::_10 is not a member of qi "

error when compiling grammar for qi.

Is there a way to increase the maximum allowed?

回答1:

Off-hand: Avoid the code smell of large numbers of function arguments.

That said,

Before:

Live On Coliru

#define SPIRIT_ARGUMENTS_LIMIT 10
#include <boost/spirit/include/qi.hpp>

int main() {
    auto& _10 = boost::spirit::labels::_10;
}

After:

Live On Coliru

#define SPIRIT_ARGUMENTS_LIMIT 11
#include <boost/spirit/include/qi.hpp>

int main() {
    auto& _10 = boost::spirit::labels::_10;
}

BONUS

You can cheat and hard-code your own placeholders:

boost::phoenix::actor<boost::spirit::argument<998> > const _999;

Note the discrepancy between 998 and _999; this is an implementation detail that is not documented, so it's probably better not rely on it, or at least have tests.

来源：https://stackoverflow.com/questions/54034181/compile-error-due-boost-spirit-placeholder-limit-not-more-than-10