[Boost-users] Simple XML parser - error handling - line number

I see tutorial sample: https://www.boost.org/doc/libs/1_67_0/libs/spirit/example/qi/mini_xml3.cpp <https://www.boost.org/doc/libs/1_67_0/libs/spirit/example/qi/mini_xml3.cpp> on_error<fail> ( xml , std::cout << val("Error! Expecting ") << _4 // what failed? << val(" here: \"") << construct<std::string>(_3, _2) // iterators to error-pos, end << val("\"") << std::endl ); How print line number, or how print _2 and _3 . If I write _2 instead _4, is compiler error. -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Users-f2553780.html