9 Iterators library [iterators]

9.7 Iterator adaptors [iterators.predef]

9.7.8 Unreachable sentinel [unreachable.sentinels]

9.7.8.2 unreachable operations [unreachable.sentinel.ops]

9.7.8.2.2 operator!= [unreachable.sentinel.op!=]

template <Iterator I> constexpr bool operator!=(const I& x, unreachable y) noexcept; template <Iterator I> constexpr bool operator!=(unreachable x, const I& y) noexcept;

Returns: true.