[Boost-users] Boost Log: Use of operator<<

Subject: [Boost-users] Boost Log: Use of operator<<
From: Florian Lindner (mailinglists_at_[hidden])
Date: 2016-01-21 08:30:57

Hello,

I want to put a custom object called DynamicVector on the BOOG_LOG_SEV
stream.

For that I defined an operator<<

template<typename Vector>
typename std::enable_if<tarch::la::IsVector<Vector>::value,
std::ostream&>::Type operator<< (std::ostream & os, const Vector &
vector);

IsVector<Vector> will be true, since

template<typename Scalar>
struct IsVector<DynamicVector<Scalar> >
{
   static const int value = true;
};

The operator itself is working:

// getCoords returns a DynamicVector<double> 
std::cout << inMesh->vertices()[j].getCoords(); 
// compiles just fine.

but

 BOOST_LOG_SEV(_log, boost::log::trivial::severity_level::error) <<
 inMesh->vertices()[j].getCoords();

gives an compile error:

/usr/include/boost/log/utility/formatting_ostream.hpp:799:19: error:

invalid operands to binary expression ('ostream_type' (aka
'basic_ostream<char_type, traits_type>') and 'const
tarch::la::DynamicVector<double>') strm.stream() << value;

str.stream() seems to be an ostream_type which is an
basic_ostream<char_type, traits_type>. 

I wonder why this isn't convertible to std::ostream, like

http://stackoverflow.com/questions/17269499/overloading-operator-for-boost-logging-object

and the comment at

http://www.boost.org/doc/libs/1_54_0/boost/log/utility/formatting_ostream.hpp

suggest.

Any help appreciated!

Thanks,
Florian