Parse an integer with non-digits in between using boost spirit

Question

I am trying to parse the numeric value from a string with non-digits in between. Is it possible to do it with boost spirit? For example,

std::string s = "AB1234xyz5678C9";
int x = 0;
boost::spirit::qi::parse(s.begin(), s.end(), /* Magic Input */, x);
// x will be equal 123456789

Answer 1

A bit of a hack:

weird_num = as_string[ skip(alpha) [+digit] ] [_val = stol_(_1) ];

This requires you to adapt std::stol for use in the semantic action:

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#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>

BOOST_PHOENIX_ADAPT_FUNCTION(long, stol_, std::stol, 1);
namespace qi = boost::spirit::qi;

int main()
{
    std::string const s = "AB1234xyz5678C9";
    qi::rule<std::string::const_iterator, long()> weird_num;

    {
        using namespace qi;
        weird_num = as_string[ skip(alpha) [+digit] ] [_val = stol_(_1) ];
    }

    long x = 0;
    if (boost::spirit::qi::parse(s.begin(), s.end(), weird_num, x))
        std::cout << "Got it: " << x << "\n";
}

Prints

Got it: 123456789