9 Iterators library [iterators]

9.7 Iterator adaptors [iterators.predef]

9.7.1 Reverse iterators [iterators.reverse]

9.7.1.2 reverse_iterator operations [reverse.iter.ops]

9.7.1.2.12 operator[] [reverse.iter.opindex]

constexpr reference operator[]( difference_type n) const requires RandomAccessIterator<I>;

1

Returns: current[-n-1].