template<class charT, class traits = char_traits<charT>>
class basic_string_view {

  // 7.7, basic_string_view modifiers
  constexpr void clear() noexcept;
  constexpr void remove_prefix(size_type n);
  constexpr void remove_suffix(size_type n);
  constexpr void swap(basic_string_view& s) noexcept;

};