Re: [Boost-users] ambiguous overload for operator>> error when using lexical_cast with qvm::vec

2016-09-17 12:20 GMT+03:00 kique G :

Hi,

I am trying to use lexical_cast to convert from strings to qvm vectors, but I keep getting an ambiguous operator>> error. I have overloaded the >> operator for istreams and that seems to be working fine when I use it to read from a istringstream. In a lexical_cast, though, I get the "ambiguous overload for operator>>" error. I have tried declaring my operator>> overload inside the std and boost::qvm namespaces to check if it was something related to ADL, but I keep getting the same error. The thing is the other candidates do not seem to make a lot of sense to me. Could somebody please tell me what I am doing wrong?

Thanks in advance,

Enrique Garcia

This is a minimal example (I am building gcc/boost from the last versions on their repositories):

#include <iostream> #include #include

std::ostream& operator<<(std::ostream& out, boost::qvm::vec const& v) { out << "(" << v.a[0] << "," << v.a[1] << "," << v.a[2] << ")"; }

std::istream& operator>>(std::istream& in, boost::qvm::vec& v) { char c; return in >> c >> v.a[0] >> c >> v.a[1] >> c >> v.a[2] >> c; }

int main() { boost::qvm::vec vect { 1.0f, 2.0f, 3.0f }; std::cout << vect << std::endl;

// This code works just fine. (4.0,5.0,6.0) is printed std::istringstream istream("(4.0,5.0,6.0"); istream >> vect; std::cout << vect << std::endl;

// This code generates an ambiguous overload for operator>> error (see below) vect = boost::lexical_cast>("(1.0,2.0,3.0)"); std::cout << vect << std::endl;

return 0; }

You have defined the operator << and operator>> in global namespace instead of namespace boost::qvm. So those operators could not be found using ADL. Try adding `namespace boost { namespace qvm {` and `}}` around them and everything must work well. Note that defining anything in boost::* namespace is not portable, not recommended and will definitely break some time. Take a closer look at the Boost.QVM and fill a feature request if QVM does not have istream operators. -- Best regards, Antony Polukhin