toString override in C++ [duplicate]

std::ostream & operator<<(std::ostream & Str, Object const & v) { 
  // print something from v to str, e.g: Str << v.getX();
  return Str;
}

If you write this in a header file, remember to mark the function inline: inline std::ostream & operator<<(... (See the C++ Super-FAQ for why.)