boost::log::operator<<
// In header: <boost/log/utility/manipulators/to_log.hpp> template<typename CharT, typename TraitsT, typename AllocatorT, typename T, typename TagT> basic_formatting_ostream< CharT, TraitsT, AllocatorT > & operator<<(basic_formatting_ostream< CharT, TraitsT, AllocatorT > & strm, to_log_manip< T, TagT > manip);