Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::stl_interfaces::operator!=
// In header: <boost/stl_interfaces/iterator_interface.hpp> template<typename IteratorInterface1, typename IteratorInterface2> decltype(v1_dtl::derived_iterator(lhs), !(lhs==rhs)) operator!=(IteratorInterface1 lhs, IteratorInterface2 rhs);