24 Ranges library [ranges]

24.5 Range utilities [range.utility]

24.5.3 View interface [view.interface]

24.5.3.2 Members [view.interface.members]

constexpr decltype(auto) front() requires forward_­range<D>; constexpr decltype(auto) front() const requires forward_­range<const D>;
Preconditions: !empty() is true.
Effects: Equivalent to: return *ranges​::​begin(derived());
constexpr decltype(auto) back() requires bidirectional_­range<D> && common_­range<D>; constexpr decltype(auto) back() const requires bidirectional_­range<const D> && common_­range<const D>;
Preconditions: !empty() is true.
Effects: Equivalent to: return *ranges​::​prev(ranges​::​end(derived()));