template<class charT, class traits>
basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& os,
basic_string_view<charT, traits> str);
Effects: Behaves as a formatted output function of os. Forms a character sequence seq, initially consisting of the elements defined by the range [str.begin(), str.end()). Determines padding for seq as described in [ostream.formatted.reqmts]. Then inserts seq as if by calling os.rdbuf()->sputn(seq, n), where n is the larger of os.width() and str.size(); then calls os.width(0).