...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::v1::v1_dtl::decrementable_sentinel<Range, void_t< decltype(--std::declval< sentinel_t< Range > & >())>>
// In header: <boost/stl_interfaces/fwd.hpp> template<typename Range> struct decrementable_sentinel<Range, void_t< decltype(--std::declval< sentinel_t< Range > & >())>> : public true_type { };