• All forms return a random-access iterator for the end of the reverse iteration over the string (the
position before the first character).
• Note that the character at the reverse end is not defined. Thus, *s.rend() and *s.crend()
result in undefined behavior.
• If the string is empty, the call is equivalent to rbegin() or crbegin().
• For details about reverse iterators, see Section 9.4.1, page 448.