std::basic_string_view<CharT,Traits>::back

constexpr const_reference back() const;

(since C++17)

Returns reference to the last character in the view. The behavior is undefined if empty() == true.

(none).

Reference to the last character, equivalent to operator[](size() - 1).

Constant.

front	accesses the first character (public member function)
empty	checks whether the view is empty (public member function)